We recently blogged about the final chapter (at the district court level, anyway) of the big defense win in the Mirena MDL.  The long-overdue result was entry of summary judgment for the defendant against all claims.  As the blog also chronicled, the key Mirena decision had been earlier – and was already appealed and affirmed – Daubert required exclusion of the plaintiffs’ general causation experts.

We’re not revisiting that today.  However, in reading the recent opinion, though, we noticed this:

As an appendix to its submissions in support of its motion for summary judgment, [defendant] has supplied citations to hundreds of cases from . . . 53 jurisdictions. . . .   [Defendant] cites this authority to support . . . the argument[s] . . . that general causation is an element of complex products liability tort claims, and . . . that general causation in such cases requires proof in the form of expert testimony. . . .  The Court is persuaded that every jurisdiction requires a showing of general causation in cases, like this one, in which a plaintiff alleges that the use of a product gave rise, through a complex causal mechanism, to a medical injury or impairment.

In re Mirena IUS Levonorgestrel-Related Products Liability Litigation (No. II), ___ F. Supp.3d ___, 2019 WL 2433552, at *9 n.2 (S.D.N.Y. June 11, 2019) (emphasis added).

Well, well well. . . .  A collection of cases requiring expert testimony in “complex” causation product liability cases from 53 jurisdictions?   Sounds like something right up the DDLaw Blog’s alley.  It’s a publicly filed document, we have a PACER account, and we know how to use it.  So we located and downloaded the aforementioned appendix, and used it as the starting point for this post – and it was a very good starting point, indeed (kudos to defense counsel’s research) – for the 50-state survey that follows.

We’ve endeavored to collect as many no-expert prescription medical product liability litigation dismissals as we could find, as well as similar decisions in other product liability and toxic tort cases.  Along with selected caselaw from every state, we’ve produced fifty states’ worth of precedent that, we hope, means that none of our clients will ever have to start from scratch again, should they feel the need to present similar research in support of the expert witness requirement that prevailed in Mirena – that all states require dismissal of prescription medical product liability plaintiffs who lack admissible expert witnesses.

To start, we found a number of cases, some mentioned in the Mirena opinion, holding broadly that “every state in the union” – or some equivalent phrase − require expert-based evidence in complex product liability cases, concern causation and/or defect issues.  First, of course, there is Mirena itself:  “all relevant jurisdictions require some evidence of general causation in products liability cases involving complex products liability (or medical) issues.”  2019 WL 2433552, at *9.

It is well established that expert testimony is required to establish causation where the issue of causation is beyond the knowledge of lay jurors.  Other courts, surveying the law of the 50 states and territories, have concluded that each jurisdiction typically adheres to this principle.

*          *          *          *

[G]enerally in products liability cases involving complex causation issues, including cases involving pharmaceuticals or medical devices, to establish causation, plaintiffs must offer admissible expert testimony regarding both general causation and specific causation. There are many holdings in accord.

Id. at *11-12 (citations and quotation marks omitted).

[A]ll jurisdictions have a similar rule requiring expert testimony where a matter is outside the ken of an ordinary lay juror.  Because [the product] is a medical device and the theory of secondary perforation is a concept requiring a nuanced understanding of . . . anatomy, the Court has no serious doubt that all jurisdictions would treat this issue as one requiring expert testimony to prove causation.

In re Mirena IUD Products Liability Litigation, 202 F. Supp.3d 304, 313 (S.D.N.Y. 2016), aff’d, 713 F. Appx. 11, 16 (2d Cir. 2017) (“Plaintiffs have not identified any state that does not require expert testimony in the circumstances at issue here”).  See also Barnes v. Anderson, 202 F.3d 150, 159 (2d Cir. 1999) (“[t]he requirement that plaintiffs produce expert medical evidence in order to prove proximate causation of medical injury also is often expressed”) (applying federal law); In re Lipitor Marketing, Sales Practices & Products Liability Litigation, 227 F. Supp.3d 452, 469 (D.S.C. 2017) (“While the specific language used by courts varies to some degree, all jurisdictions require expert testimony at least where the issues are medically complex and outside common knowledge and lay experience.”); In re Lipitor (Atorvastatin Calcium) Marketing, Sales Practices & Products Liability Litigation, 226 F. Supp.3d 557, 569-70 (D.S.C. 2017) (same); In re Zoloft (Sertraline hydrochloride) Products Liability Litigation, 176 F. Supp.3d 483, 490 (E.D. Pa. 2016) (“Plaintiffs have not cited cases from any jurisdiction holding that the complex scientific question of whether a prescription drug is a teratogen can be answered without expert testimony or based on circumstantial evidence, and the legal principles upon which the Court has relied tend to be consistent across jurisdictions.”), aff’d, 858 F.3d 787 (3d Cir. 2017); In re Bausch & Lomb, Inc. Contacts Lens Solution Products Liability Litigation, 693 F. Supp.2d 515, 518 (D.S.C. 2010) (Under the law of “all the applicable jurisdictions,” “plaintiffs’ claims cannot survive” after “plaintiffs’ only general causation expert, has been excluded.”), aff’d, 429 F. Appx. 249 (4th Cir. 2011); In re Rezulin Products Liability Litigation, 441 F. Supp.2d 567, 575 & n.68 (S.D.N.Y. 2006) (expert causation testimony in prescription medical product liability litigation “is a requirement in every state in which these plaintiffs have brought their claims”); In re Phenylpropanolamine (PPA) Products Liability Litigation, 2003 WL 27382559, at *1 (W.D. Wash. Oct. 24, 2003) (“Given the medically and scientifically complex nature of this litigation, expert testimony is crucial to the establishment of causation.”); In re Norplant Contraceptive Products Liability Litigation, 215 F. Supp.2d 795, 830, 833 (E.D. Tex. 2002) (“[e]vidence of general causation must be provided in the form of expert testimony”; summary judgment granted; “Plaintiffs have not produced a shred of evidence or expert testimony that supports an association between Norplant and any of the [more than 950] exotic conditions”).

PART ONE

Anyway, as our research often does, this project became much more substantial than we originally expected.  The law was more extensive than we thought, and to do it justice required going beyond prescription medical product liability litigation.  So in order not to overwhelm our readers with too much at once, we’ve decided to break this 50-state survey – at least initially – into three roughly equal parts.  Part one is Alabama through maritime law.

Alabama

Under Alabama law, expert testimony is required to establish causation where “the nature and origin” of the injury is “beyond the understanding of the average person.”  Ex parte Trinity Industries, Inc., 680 So.2d 262, 269 (Ala. 1996).  Thus, “[p]laintiffs must prove the toxicity of [a product] and that it had a toxic effect on them causing the injuries that they suffered,” and “[t]his type of proof requires expert testimony.”  McClain v. Metabolife International, Inc., 401 F.3d 1233, 1237 (11th Cir. 2005) (applying Alabama law).

The interaction between a complex and technical medical device and the unique physiological and medical circumstances of the patient in which it is implanted is a subject on which no ordinary juror could rationally be expected to have knowledge.  The net result is that, without the benefit of expert testimony, a reasonable jury could not possibly make a determination . . . that [plaintiff’s] injuries were caused by a . . . defect in the [product].

Hughes v. Stryker Sales Corp., 2010 WL 1961051, at *5 (S.D. Ala. May 13, 2010), aff’d, 423 F. Appx. 878, 881 (5th Cir. 2011) (on basis of district court’s reasoning).  “[I]n the typical case involving a complex medical device, the absence of expert testimony would force a jury to engage in speculation and conjecture on issues of defect and causation,” thus “courts routinely require expert testimony in such matters.”  Id.

Thus, “Alabama courts consistently have opined that . . ., when the product at issue is of a complex and technical nature, the plaintiff’s proof of a defect should be in the form of expert testimony. Bloodsworth v. Smith & Nephew, Inc., 476 F. Supp.2d 1348, 1353 n.3 (M.D. Ala. 2006).  See Drake v. Ortho-McNeil-Janssen Pharmaceuticals, 2018 WL 1431646 (N.D. Ala. March 22, 2018) (“[d]ue to the complex nature of the claims, expert testimony generally is required to establish general and specific causation in product liability cases”); Brantley v. International Paper Co., 2017 WL 2292767, at *16 (M.D. Ala. May 24, 2017) (“The plaintiffs must establish both general and specific causation through expert evidence.”); Jones v. Novartis Pharmaceuticals Corp., 2017 WL 553134, at *17 (N.D. Ala. Feb. 10, 2017) (“plaintiffs must provide expert testimony to establish both general and specific causation”), aff’d, 720 F. Appx. 1006 (11th Cir. 2018); Benkwith v. Matrixx Initiatives, Inc., 467 F. Supp.2d 1316, 1332 (M.D. Ala. 2006) (plaintiff “must present expert evidence on general causation.  Without proof of causation, she cannot prevail”) (citation omitted); Sutherland v. Matrixx Initiatives, Inc., 2006 WL 6617000, at *14 (N.D. Ala. 2006) (“without an expert to connect a toxin to an injury, there is no toxic tort”); Emody v. Medtronic, Inc., 238 F. Supp.2d 1291, 1295 (N.D. Ala. 2003) (“An essential element of all product liability cases is expert testimony . . . that a defect was the medical cause of plaintiff’s claimed injuries.”).

Alaska

Expert testimony is required in Alaska to establish a causal connection “where there is no reasonably apparent . . . causal relationship between the event demonstrated and the result sought to be proved.”  Choi v. Anvil, 32 P.3d 1, 3 (Alaska 2001) (citation and quotation marks omitted).  This question is one “of law to which we apply our independent judgment.”  D.P. v. Wrangell General Hospital, 5 P.3d 225, 228 (Alaska 2000).  Thus, a plaintiff is “required by law to support his claim with expert testimony unless the causation of his alleged injury was of a non-technical nature.”  Parker v. Tomera, 89 P.3d 761, 766 (Alaska 2004).  See Voyles v. State, 2008 WL 4951416, at *18 (Alaska App. Nov. 19, 2008) (“The test is whether the basis of the [casual] conclusion (once explained) can be readily understood and assessed by lay jurors.”); Coppe v. Bleicher, 2008 WL 8614177 (Alaska Super. Aug. 29, 2008) (“Expert testimony is required to establish medical causation when the nature and character of a person’s injuries require the special skill of an expert to render the evidence comprehensible.”); Gallant v. United States, 392 F. Supp.2d 1077, 1080-81 (D. Alaska 2005) (expert testimony required in any case that “is not a situation where negligence could be evident to a lay person”) (footnote omitted).

Arizona

In Arizona litigation, “[w]hen [a] causal connection is not readily apparent, it must be established by expert medical testimony”  Aguayo v. Industrial Commission, 333 P.3d 31, 33-346 (Ariz. App. 2014).  Thus, “[w]here causation is peculiarly within the knowledge of medical experts . . . we must rely upon the opinion of medical experts.”  McNeely v. Industrial Commission, 501 P.2d 555, 557 (Ariz. 1972).  “Expert medical testimony is . . . generally required to establish proximate cause unless a causal relationship is readily apparent to the trier of fact.”  Rasor v. Northwest Hospital, LLC, 373 P.3d 563, 566 (Ariz. App. 2016), rev’d on other grounds, 403 P.3d 572 (Ariz. 2017) (holding plaintiff’s expert unqualified).  See also Clemens v. DMB Sports Clubs Ltd. Partnership, 2015 WL 8166584, at *3 (Ariz. App. Dec. 8, 2015) (“the plaintiff must prove the cause of . . . physical injury damages through expert medical testimony, unless a causal relationship is readily apparent to the trier of fact”) (citation and quotation marks omitted); Gentry v. Daugherity, 2015 WL 1346097, at *3 (D. Ariz. March 24, 2015) (“Unless an injury is obvious to the jury, expert medical testimony is required to establish the nature and extent of the injury as well as its relationship to the accident.”); Cloud v. Pfizer, Inc., 198 F. Supp.2d 1118, 1138-39 (D. Ariz. 2001) (a plaintiff “cannot prove causation” “in the absence” of expert testimony).

Arkansas

Arkansas requires expert testimony regarding causation in the “vast majority of our cases” where it involves medical issues that are “not within the comprehension of a jury of laymen.”  Mitchell v. Lincoln, 237 S.W.3d 455, 599 (Ark. 2006).  “Except in the most obvious cases, such causation must be established by expert medical testimony.”  Baldwin v. Club Products Co., 604 S.W.2d 568, 570 (Ark. App. 1980).  Where a plaintiff’s “alleged resulting injuries involved complex medical issues outside the jury’s common knowledge, . . . expert testimony was necessary.”  Engleman v. McCullough, 535 S.W.3d 643, 649 (Ark. App. 2017).

In product liability “to prove a defect by showing a safer alternative design . . . [plaintiff] could not meet his burden without an expert.”  Anderson v. Raymond Corp., 340 F.3d 520, 524 (8th Cir. 2003) (applying Arkansas law).  Thus, “Whether proceeding on a negligence or strict liability theory, a plaintiff in a toxic tort case must, under Arkansas law, establish medical causation through expert testimony.”  National Bank of Commerce v. Associated Milk Producers, Inc., 22 F. Supp.2d 942, 949 (E.D. Ark. 1998), aff’d, 191 F.3d 858 (8th Cir. 1999).  “Under Arkansas law, expert witness testimony is required to prove that any negligence of Defendants was a proximate cause of Plaintiff’s injuries, as Plaintiff in this case alleged medical injuries based on a theory that involved complex determinations of medical issues.”  Isham v. Booneville Community Hospital, 2015 WL 4133098, at *2 (W.D. Ark. July 8, 2015).

California

California law establishes that “the decisive consideration in determining the necessity of expert opinion evidence is whether the subject of inquiry is one of such common knowledge that persons of ordinary education could reach a conclusion as intelligently as the witness or whether, on the other hand, the matter is sufficiently beyond common experience that the opinion of an expert is required.”  Campbell v. General Motors Corp., 649 P.2d 224, 231 (Cal. 1982).  “In cases like the one before us, presenting complicated and possibly esoteric medical causation issues, the standard of proof ordinarily required is ‘a reasonable medical probability based upon competent expert testimony that the defendant’s conduct contributed to [the] plaintiff’s injury.’”  Bockrath v. Aldrich Chemical Co., 980 P.2d 398, 403 (Cal. 1999) (quoting Rutherford v. Owens-Illinois, Inc., 941 P.2d 1203, 1219 n.11 (Cal .1997)).  Where “the complexity of the causation issue is beyond common experience, expert testimony is required to establish causation.”  Stephen v. Ford Motor Co., 37 Cal. Rptr.3d 9, 17 (Cal. App. 2005).  See Miranda v. Bomel Construction Co.,. 115 Cal. Rptr.3d 538, 545-46 (Cal. App 2010) (“The law is well settled that in a personal injury action causation must be proven within a reasonable medical probability based upon competent expert testimony.”); People v. Racy, 56 Cal. Rptr.3d 455, 460 (2007) (“expert testimony would have been necessary because the effects of [the product] . . . are matters beyond the experience of average jurors”); Jones v. Ortho Pharmaceutical Corp., 209 Cal. Rptr. 456, 461 (Cal. App. 1985) (“the unknown and mysterious etiology of cancer” is “beyond the experience of laymen and can only be explained through expert testimony”).

Thus, “In California, ‘in a personal injury action causation must be proven within a reasonable medical probability based upon competent expert testimony.’”  Avila v. Willits Environmental Remediation Trust, 633 F.3d 828, 836 (9th Cir. 2011) (quoting Jones, 209 Cal. Rptr. at 460).

The law is well-settled that in a personal injury action causation must be proven within a reasonable medical probability based upon competent expert testimony.  And where, as here, the complexity of the causation issue is beyond common experience, expert testimony is required to establish causation.

Brown v. Johnson & Johnson, 2019 WL 2577296, at *5 (E.D. Cal. June 24, 2019) (citations and quotation marks omitted).  See Nelson v. Matrixx Initiatives, Inc., 592 F. Appx. 591, 592 (9th Cir. 2015) (“General and specific causation” “must be proven within a reasonable medical probability based upon competent expert testimony.”) (also quoting Jones) (applying California law); Pierson v. Ford Motor Co., 445 F. Appx. 966, 968 (9th Cir. 2011) (quoting Stephen) (applying California law); In re Baycol Products Litigation, 596 F.3d 884, 889 (8th Cir. 2010) (“To succeed in his strict liability and negligence claims, [plaintiff] has the burden of proving medical causation through the use of a medical expert.”) (citing Bockrath) (applying California law); Shalaby v. Newell Rubbermaid, Inc., 379 F. Appx. 620, 623 (9th Cir. 2010 (where “the plaintiffs had not presented the expert testimony required to establish causation . . ., the plaintiffs had not established a prima facie case”) (quoting Stephen) (applying California law); Viramontes v. Pfizer, Inc., 2018 WL 3363699, at *9 (E.D. Cal. July 10, 2018) (“The applicable law requires that ‘in a personal injury action causation must be proven within a reasonable medical probability based upon competent expert testimony.’”) (also quoting Jones); Sclafani v. Air & Liquid Systems Corp., 14 F. Supp.3d 1351, 1355 (C.D. Cal. 2014) (issues of causation “beyond the experience of laymen . . . can only be explained through expert testimony”); Thomas v. Abbott Laboratories, 2014 WL 4197494, at *11 (C.D. Cal. July 29, 2014) (“Where causation is beyond a jury’s experience, it is the expert who must rule out the other possible causes.”); Sanchez v. Stryker Corp., 2012 WL 1570569 at *6 (C.D. Cal. May 2, 2012) (“Probable causes in a medical tort case are beyond the experience of laymen and can only be explained through expert testimony.”); Cox v. Depuy Motech, Inc., 2000 WL 1160486, at *7 (S.D.Cal. March 29, 2000) (“Because plaintiff does not have an expert who can establish medical causation, an essential element of a products liability claim, plaintiff cannot withstand defendant’s motion for summary judgment on the issue of causation.”); Huntman v. Danek Medical, Inc., 1998 WL 663362, at *3–4 (S.D.Cal. July 24, 1998) (“[i]n the absence of expert testimony . . . plaintiff’s strict liability and negligence claims must fail”); Sanderson v. International Flavors & Fragrances, Inc., 950 F. Supp. 981, 985 (C.D. Cal. 1996)  (“It should be emphasized that expert testimony is required to establish causation, since this case involves scientific issues that are beyond the experience of laymen.”).

Colorado

Under Colorado law, when “the applicable standard is not within the common knowledge and experience of ordinary persons, the applicable standard must be established by expert testimony.”  United Blood Services, a Div. of Blood Systems, Inc. v. Quintana, 827 P.2d 509, 520 (Colo. 1992).  Expert testimony is required for any “complex medical question outside lay competence.”  Mathison v. United States, 619 F. Appx. 691, 694 (10th Cir. 2015) (applying Colorado law).

Thus, “[u]nder Colorado law, products liability claims involving matters outside the experience of the average layperson, like negligence claims involving such complex or technical issues, require expert testimony to prove issues such as causation.”  Xtreme Coil Drilling Corp. v. Encana Oil & Gas (USA), Inc., 2010 WL 3777303, at *7 (D. Colo. Sept. 19, 2010).  Thus, Colorado law “require[s] expert witness testimony to establish the causal link between complex injuries and [an] incident.”  Sanchez-Ironshell v. Brinker Restaurant Corp., 2017 WL 5990090, at *3 (D. Colo. June 15, 2017).  See Truck Insurance Exchange v. MagneTek, Inc., 360 F.3d 1206, 1215 (10th Cir. 2004) (“without the excluded expert testimony . . ., a jury could not reasonably make the necessary inference that the [product] caused the [accident]”) (applying Colorado law); Brown v. Johnson & Johnson, 2016 WL 897021, at *1 (D. Colo. March 9, 2016) (“these injuries were allegedly caused by chemicals working within [plaintiff’s] body.  A lay jury does not have the competence to conclude, based on everyday experience, that [a drug] in fact caused [plaintiff’s] injuries.”); Howell v. Centric Group, LLC, 2011 WL 4499372, at *5 (D. Colo. Sept. 27, 2011) (“where questions of causation are beyond the knowledge and experience of ordinary persons, expert testimony may be required”), aff’d, 508 F. Appx. 834, 836 (10th Cir. 2013) (“[w]here an injury has multiple potential etiologies, expert testimony is necessary to establish causation”) (citation and quotation marks omitted) (applying Colorado law).

Connecticut

In Connecticut, “[i]f lay witnesses and common experience are not sufficient to remove the case from the realm of speculation, the plaintiff will need to present expert testimony to establish a prima facie case.”  Metropolitan Property & Casualty Insurance Co. v. Deere & Co., 25 A.3d 571, 584 (Conn. 2011).  Thus, “[d]epending on the type of product at issue − namely, its complexity − expert testimony regarding product defect or causation may be required in order to make out a prima facie product liability case.”  D’Ascanio v. Toyota Industrial Corp., 72 A.3d 1019, 1026 (Conn. 2013).  Accord Bagley v. Adel Wiggins Group, 171 A.3d 432, 447 (Conn. 2017) (“proof [of asbestos exposure] required the assistance of an expert because the subject matter was technical in nature and beyond the field of ordinary knowledge of a lay juror.  Because the plaintiff did not produce an expert, she failed to prove her case.”); Santopietro v. City of New Haven, 682 A.2d 106 (Conn. 1996) (“If the determination of the standard of care requires knowledge that is beyond the experience of an ordinary fact finder, expert testimony will be required.”).

“When the causation issue involved goes beyond the field of ordinary knowledge and experience of judges and jurors, expert testimony is required.”  Theodore v. Lifeline Systems Co., 163 A.3d 654, 666 (Conn. App. 2017) (citation and quotation marks omitted).  “[W]e . . . consistently have held that expert testimony is required when the question involved goes beyond the field of the ordinary knowledge and experience of judges or jurors.”  White v. Mazda Motor, Inc., 54 A.3d 643, 650 (Conn. App. 2012) (citation and quotation marks omitted), aff’d, 99 A.3d 1079 (Conn. 2014).

Proof that a defect in the product caused the injury in controversy is a prerequisite to recovery for product-caused injury in every products liability case. . . .  When the causation issue involved goes beyond the field of ordinary knowledge and experience of judges and jurors, expert testimony is required.  The product at issue in the present case is a complex product:  a spinal system . . . implanted into the patient’s spine. . . .  Accordingly, we agree with the trial court’s determination that expert testimony was required to establish causation.

Ferrari v. Johnson & Johnson, Inc., ___ A.3d ___, 2019 WL 2167849, at *6 (Conn. App. May 21, 2019).  Accord Milton v. Robinson, 27 A.3d 480, 493 (Conn. App. 2011) (expert testimony mandatory in case that “concerns complex details regarding the adequacy of a phase III clinical study and standards of care in designing experimental drugs”).

Thus, “Connecticut courts consistently hold ‘that expert testimony is required when the question involved goes beyond the field of the ordinary knowledge and experience of judges or jurors.’” Brown v. Johnson & Johnson Pharmaceuticals, 2015 WL 235135, at *3 (D. Conn. Jan. 16, 2015) (quoting White).  “[W]ithout expert medical testimony causally linking [the drug] to [plaintiff’s] injuries, a reasonable jury could not find that it is more probable than not that [the drug] caused [those] injuries.”  Id. at *4.  See Grenger v. General Electric Co., 2019 WL 2743577, at *2 (D. Conn. July 1, 2019) (entering summary judgment because “[w]ithout competent expert testimony, plaintiff will be unable to demonstrate” exposure); Beyer v. Anchor Insulation Co., 238 F. Supp.3d 270, 294 (D. Conn. 2017) (“The complexity of the causal link between [the product] and Plaintiffs’ health problems necessitates expert testimony as to general causation.”); K.E. v. GlaxoSmithKline LLC, 2017 WL 440242, at *26 (D. Conn. Feb. 1, 2017) (summary judgment granted in prescription medical product liability case after plaintiffs’ experts excluded); Sullivan v. Pfizer, Inc., 2016 WL 868155, at *4 n.4 (D. Conn. March 4, 2016) (“Because prescription drugs and their effects on the human body are complex issues, Sullivan cannot avoid the need for expert testimony by relying on the doctrine of res ipsa loquitur.”); Walters v. Howmedica Osteonics Corp., 676 F. Supp.2d 44, 52 (D. Conn. 2009) (“the standard of care that the designer and manufacturer of [a medical device] must follow lay beyond the experience and ken of the ordinary fact finder”; summary judgment entered for lack of expert testimony) (citation and quotation marks omitted); Koger v. Synthes North America, Inc., 2009 WL 5110780, at *3 (D. Conn. Dec. 17, 2009) (“plaintiff’s proof of defect and causation involves complex issues, requiring expert testimony”); Gold v. Dalkon Shield Claimants Trust, 1998 WL 351456, at *3 (D. Conn. June 15, 1998) (“without a proffer of expert medical testimony as to causation to link the defect to the injury, a reasonable jury could not find that the plaintiff has proved that the defect caused her specific injuries”), aff’d, 189 F.3d 460 (2d Cir. 1999).

Delaware

“It is settled Delaware law that, if a claim requires proof of facts that are “not within the common knowledge of laymen,” those facts “must be presented through competent expert testimony.”  Campbell v. DiSabatino, 947 A.2d 1116, 1118 (Del. 2008).  “When the plaintiff’s claim involves bodily injuries, the causal connection between the defendant’s alleged negligent conduct and the plaintiff’s alleged injury must be proven by the direct testimony of a competent medical expert.”  Roache v. Charney, 38 A.3d 281, 286 (Del. 2012).  “[I]f the matter in issue is one within the knowledge of experts only and not within the common knowledge of laymen, it is necessary for the plaintiff to introduce expert testimony in order to establish a prima facie case.”  Money v. Manville Corp. Asbestos Disease Compensatory Trust Fund, 596 A.2d 1372, 1375 (Del. 1991) (citations and quotation marks omitted).

If a party intends to make an argument involving an issue that is within the knowledge of experts only and not within the common knowledge of laymen, the party must present competent expert testimony to support that argument.  Expert testimony is required where a reasoned decision on the question of proximate cause may require understanding and analysis of issues beyond the ken of the typical jury.

Davis v. Maute, 770 A.2d 36, 40 n.3 (Del. 2001) (citations and quotation marks omitted).

Thus, “[i]n pharmaceutical cases such as this, involving complex scientific evidence, a plaintiff must present expert witnesses to provide evidence of both general and specific causation.”  Scaife v. Astrazeneca LP, 2009 WL 1610575, at *20 (Del. Super. June 9, 2009) (footnote omitted).  See Hopkins v. Janssen Pharmaceuticals, Inc., 2019 WL 1567840, at *2 (D. Del. April 11, 2019) (granting summary judgment because “Plaintiff cannot establish proximate cause, as a matter of law, because he has not produced an expert report”); Guinan v. A.I. duPont Hospital for Children, 597 F. Supp.2d 517, 533 (E.D. Pa. 2009) (summary judgment granted where plaintiff’s expert’s “report is devoid of an opinion regarding causation”) (applying Delaware law), aff’d, 393 F. Appx. 884 (3d Cir. 2010); Collis v. Topper’s Salon & Health Spa, Inc., 2013 WL 4716237, at *2 (Del. Super. Aug. 29, 2013) (“Medical expert testimony regarding causation is required when there is a claim for bodily injuries, regardless of the nature of the negligence involved.”); Gunzl v. Warner’s Moving & Storage, Inc., 1993 WL 331084, at *3 (Del. Super. Aug. 4, 1993) (“Medical testimony is necessary to establish causation between the accident and the alleged disability if the medical question becomes sufficiently complicated so that it is within the field of medical experts.”).

District of Columbia

District of Columbia litigants must produce expert testimony “in cases presenting medically complicated questions due to multiple and/or preexisting causes.”  Baltimore v. B.F. Goodrich Co., 545 A.2d 1228, 1231 (D.C. 1988).  “Our rule for medically complicated cases is that proof of causation normally requires medical opinion testimony.”  Lasley v. Georgetown University, 688 A.2d 1381, 1384 (D.C. 1997).  “In cases presenting medically complicated questions . . ., we have held that expert testimony is required on the issue of causation.”  Brin v. S.E.W. Investors, 902 A.2d 784, 793 (D.C. 2006) (quoting Williams v. Patterson, 681 A.2d 1147, 1150 (D.C. 1996)).

Federal courts apply the expert requirement to all defect and causation questions.  “D.C. law often requires expert testimony in tort cases even when the facts underlying the plaintiff’s injury might seem fairly straightforward.” Davis v. Bud and Papa, Inc., 885 F. Supp.2d 85, 89 (D.D.C. 2012).  See Westinghouse Electric Corp. v. Nutt, 407 A.2d 606, 612 (D.C. 1979) (“[t]he jury needed supporting expert testimony to assess the burden of precaution to avoid harm”); Kubicki v. Medtronic, Inc., 293 F. Supp.3d 129, 156 (D.D.C. 2018) (“in complex medical product liability cases such as this one, expert testimony regarding causation is ordinarily indispensable under District of Columbia law”); Arias v. DynCorp, 928 F. Supp.2d 1, 9 (D.D.C. 2013) (“Because the nexus between the plaintiffs’ exposure and their increased risk of cancer would not be obvious to the jury, expert evidence is required to explain the underlying medical science and avoid jury guesswork or speculation as to the issue of causation.”); Halcomb v. Woods, 610 F. Supp.2d 77, 85 (D.D.C. 2009) (“expert testimony is necessary to demonstrate a causal link between a defendant’s act and a plaintiff’s harm “in cases presenting medically complicated questions”); Willis v. Besam Automated Entrance Systems, Inc., 2005 WL 2902494, at *14 (E.D. Pa. Nov. 3, 2005) (“In order to prevail on a theory of strict liability, the plaintiff must rely on expert testimony when the subject presented is so distinctly related to some science, profession, business or occupation as to be beyond the ken of the average layman.”) (citation and quotation marks omitted) (applying District of Columbia law), aff’d in pertinent part, 228 F. Appx. 246 (3d Cir. 2007); Webster v. Pacesetter, Inc., 259 F. Supp.2d 27, 34 (D.D.C. 2003) (“even if they could identify a defect, [plaintiffs] have failed to proffer evidence from an expert who can testify to a reasonable degree of certainty that the defect more likely than not caused the injuries”).

First Nations

“The Navajo Nation Supreme Court has recognized the need for expert testimony where a layperson is not qualified to provide a reliable analysis.”  Harvey v. United States, 685 F.3d 939, 955 (10th Cir. 2012) (applying Navajo law).  “Diagnosis of an individual requires professional expertise; when such a diagnosis is used outside the context of its professional use it introduces the risks of mischaracterizations, inaccuracy and potential prejudice and bias.”  Baldwin v. Chinle Family Court, 2008 WL 5444666 (Navajo Oct. 30, 2008).

Florida

Florida “[t]oxic tort cases . . . are won or lost on the strength of the scientific evidence presented to prove causation.”  Rink v. Cheminova, Inc., 400 F.3d 1286, 1297 (11th Cir. 2005) (applying Florida law).  Expert testimony is necessary “to establish legal causation where the issue is beyond the common knowledge of laymen.”  Benitez v. Joseph Trucking, Inc., 68 So.3d 428, 431 (Fla. App. 2011); accord Gouveia v. Phillips, 823 So.2d 215, 227 (Fla. App. 2002) (expert testimony required “when the discrete issue to be decided is not within the abilities of lay jurors”).  Likewise, “the adequacy or inadequacy of the warning to inform a physician must, except in the more obvious situations, be proved by expert testimony.”  Upjohn Co. v. MacMurdo, 562 So.2d 680, 683 (Fla. 1990).

[I]n complex cases where a jury is asked to assess complex medical or scientific issues outside the scope of a layperson’s knowledge, an expert’s testimony is required. Without expert testimony, the plaintiff’s claim fails as a matter of law.

Small v. Amgen, Inc., 723 F. Appx. 722, 726 (11th Cir. 2018) (citations and quotation marks omitted) (applying Florida law).  See Chapman v. Procter & Gamble Distributing, LLC, 766 F.3d 1296, 1316 (11th Cir. 2014) (plaintiffs “were required to have Daubert-qualified, general and specific-causation-expert testimony”) (emphasis original) (applying Florida law); Kilpatrick v. Breg, Inc., 613 F.3d 1329, 1334 n.4 (11th Cir. 2010) (following McClain, see Alabama) (applying Florida law); Hendrix v. Evenflo Co., 609 F.3d 1183, 1203 (11th Cir. 2010) (“without this [expert] testimony there is no genuine dispute of material fact regarding causation . . . [and] the district court’s grant of summary judgment on [plaintiff’s] sole remaining claim was appropriate.”) (applying Florida law); Guinn v. AstraZeneca Pharmaceuticals LP, 602 F.3d 1245, 1256 (11th Cir. 2010) (“the exclusion of [plaintiffs’ expert’s] testimony is a basis for granting summary judgment”) (applying Florida law); In re Diet Drugs (Phentermine/Fenfluramine/Dexfenfluramine) Products Litigation, 85 F. Appx. 845, 847 (3d Cir. 2004) (“under Florida law [plaintiff] must present expert testimony regarding causation in order to sustain his suit”) (applying Florida law); Tonelli v. NCL (Bahamas) Ltd., 2019 WL 935384 (S.D. Fla. Feb. 26, 2019) (“In Florida, cases involving complicated medical questions require expert opinions to establish causation.”); In re Abilify (Aripiprazole) Products Liability Litigation, 299 F. Supp.3d 1291, 1306 (N.D. Fla. 2018) (“To prevail in a pharmaceutical products liability case, a plaintiff must establish both general and specific causation through reliable expert testimony.”); Bryant v. C. R. Bard, Inc., 2017 WL 2350228, at *3 (S.D.W. Va. May 30, 2017) (with expert testimony stricken, plaintiff “has not produced any evidence to show medical causation”) (applying Florida law); Olmo v. Davol, Inc., 2017 WL 1367231, at *6-7 (S.D. Fla. April 10, 2017) (summary judgment on causation granted in medical device case after plaintiff’s experts excluded), aff’d, 710 F. Appx. 861 (11th Cir. 2018); Marshick v. Johnson & Johnson, 2015 WL 9266955, at *3 (M.D. Fla. Dec. 11, 2015) (“A plaintiff must prove general and specific causation by expert testimony.”); McCasland v. Pro Guard Coatings, Inc., 2018 WL 5786164, at *3 (M.D. Fla. Nov. 5, 2018) (plaintiff “must present expert testimony linking [the product] to his medical condition to meet this burden”); Payne v. C.R. Bard, Inc., 7, 2014 WL 1887297, at *2 (M.D. Fla. May 12, 2014) (“Expert testimony is generally necessary to prove that a complex product like a medical device is defective.”), aff’d, 606 F. Appx. 940 (11th Cir. 2015); Jacob v. Korean Air Lines Co., 2014 WL 1584444, at *6 (S.D. Fla. March 20, 2014) (“Although causation is an issue generally left to a jury, medical causation falls beyond the scope of a layperson’s knowledge and requires competent medical testimony.”); Faile v. Dillard’s Inc., 2011 WL 13192673, at *2 (N.D. Fla. Nov. 7, 2011) (“plaintiffs must introduce expert testimony to establish medical causation in Florida”), aff’d, 480 F. Appx. 951 (11th Cir. 2012); In re Trasylol Products Liability Litigation, 2011 WL 7109297, at *10 (S.D. Fla. April 27, 2011) (“Plaintiff must, but cannot, establish causation with competent expert testimony in this complex medical case.); Savage v. Danek Medical, Inc., 31 F. Supp.2d 980, 983 (M.D.Fla.1999) (“A defect must be proven by expert testimony”); Baker v. Danek Medical, 35 F. Supp.2d 875, 880 (N.D. Fla. 1998) (“An invitation to the jury to join in speculation is not sufficient medical causation testimony to defeat a summary judgment challenge.”).

Georgia

Georgia law mandates expert testimony “where the existence of a causal link between the defendant’s conduct and the plaintiff’s injury cannot be determined from common knowledge and experience and instead requires the assistance of experts with specialized medical knowledge.”  Cowart v. Widener, 697 S.E.2d 779, 784 (Ga. 2010).  “[E]ven in simple negligence cases, plaintiffs must come forward with expert evidence . . . where ‘medical questions’ relating to causation are involved.”  Id.  “[T]oxic tort” cases are a another “example.”  Id. at 785.  “Causation is an essential element of a toxic tort case,” and proof of causation in such cases “generally requires reliable expert testimony.”  Butler v. Union Carbide Corp., 712 S.E.2d 537, 544 (Ga. App. 2011) (footnote omitted).  Thus, Georgia “[t]oxic tort cases . . . are won or lost on the strength of the scientific evidence presented to prove causation.”  Rider v. Sandoz Pharmaceuticals Corp., 295 F.3d 1194, 1197 (11th Cir. 2002).  See Barko Response Team, Inc. v. Sudduth, 795 S.E.2d 198, 201-02 (Ga. App. 2016) (reversible error to deny summary judgment where plaintiff submitted no expert evidence in toxic mold case); Seymour Electrical & Air Conditioning Service v. Statom, 710 S.E.2d 874, 877-78 (Ga. App. 2011) (reversible error to deny summary judgment where plaintiff submitted no expert evidence in carbon monoxide poisoning case); Allstate Insurance Co. v. Sutton, 658 S.E.2d 909, 915 (Ga. App. 2008) (summary judgment affirmed in toxic mold case where plaintiff had no expert medical testimony) (punctuation and footnotes omitted).

Product liability claims fall into the same category.

That [the product] can and did cause systemic disease in [plaintiff] is not a natural inference that a juror could make through human experience. Thus, medical expert testimony was essential to prove causation in this case.

Allison v. McGhan Medical Corp., 184 F.3d 1300, 1320 (11th Cir. 1999) (applying Georgia law).  See Thurmond v. Bayer Healthcare Pharmaceuticals, Inc., 649 F. Appx. 1003, 1006, n.1 (11th Cir. 2016) (“medical expert testimony is essential in products liability actions when the theory of causation is not a natural inference that a juror could make through human experience”) (applying Georgia law); Wilson v. Taser International, Inc., 303 F. Appx. 708, 715 (11th Cir. 2008) (applying Georgia law) (“[i]n product liability cases, proof of causation generally requires reliable expert testimony”); O’Shea v. Zimmer Biomet Holdings, 342 F. Supp.3d 1354, 1364 (N.D. Ga. 2018) (design defect plaintiff “must produce evidence from an expert who . . . opine[s] that the risk inherent in the [product] design outweigh the utility or benefit derived from the product”); Roper v. Kawasaki Heavy Industries, Ltd., 2015 WL 11236553, at *20 (N.D. Ga. June 29, 2015) (“expert testimony is necessary to prove causation if the causal connection between the defective product and the plaintiff’s injuries is not a natural inference that a juror could make through human experience”); Wheeler v. Novartis Pharmaceuticals Corp., 944 F. Supp.2d 1344, 1352 (S.D. Ga. 2013) (“In products liability cases, proof of causation generally requires reliable expert testimony.”); Brown v. Roche Laboratories, Inc., 2013 WL 2457950, at *8 (N.D. Ga. June 6, 2013) (“[e]xpert testimony is . . . essential to establish causation in this case”), aff’d, 567 F. Appx. 860 (11th Cir. 2014); Parker v. Brush Wellman, Inc., 2010 WL 3730924, at *8 (N.D. Ga. Sept. 17, 2010) (“Plaintiffs’ lack of expert testimony is fatal to the causation element of their failure to warn claim”), aff’d, 445 F. Appx. 231 (11th Cir. 2011); Jack v. Glaxo Wellcome, Inc., 239 F. Supp.2d 1308, 1321 (N.D. Ga. 2002) (entering summary judgment after plaintiffs’ experts excluded in prescription medical product case); Wheat v. Sofamor, S.N.C., 46 F. Supp.2d 1351, 1361-62 (N.D. Ga. 1999) (same); Smith v. Ortho Pharmaceutical Corp., 770 F. Supp. 1561, 1565 (N.D. Ga. 1991) (“Scientific testimony by expert witnesses on the issue of causation plays an increasingly vital role in [Georgia] products liability litigation.”).

Hawai’i

Expert testimony in Hawai’i is required where “lay jurors are ill prepared to evaluate complicated technical data for the purpose of determining . . . whether there is a causal relationship between the violation of a duty and an injury to the patient.”  Exotics Hawaii-Kona, Inc. v. E.I. Du Pont De Nemours & Co., 172 P.3d 1021, 1044 (Haw. 2007) (quoting Bernard v. Char, 903 P.2d 676, 682 (Haw. App.), aff’d, 903 P.2d 667 (Haw. 1995)).  In medical causation cases, “[e]xpert medical testimony . . . was required to establish this essential element [causation] of the plaintiff’s case.”  Devine v. Queen’s Medical Center, 574 P.2d 1352, 1353 (Haw. 1978).  Where a plaintiff “sustained a ‘sophisticated injury,’ . . . a reasonable jury would need expert medical testimony to determine whether and to what extent any alleged negligence by Defendants contributed to his” injuries.  Barbee v. Queen’s Medical Center, 194 P.3d 1098, 1123 (Haw. App. 2008).

Thus, “the plaintiff is generally required to provide expert testimony to establish an element of their negligence case.”  Baker v. Gaspar, 2019 WL 984271, at *6 (D. Haw. Feb. 28, 2019).  “[B]ecause Plaintiffs-Appellants’ symptoms were medically complex, and . . . beyond the familiarity of the ordinary juror, the jury would have been incompetent to determine the issue of causation.  Consequently, expert testimony was essential to enabling the jury to determine causation.”  Kim-Alaniz v. Executive Center AOAO, 2013 WL 1943181, at *4 (Haw. App. May 10, 2013).

The same is true of product liability.  See Haake v. Safeway, 819 F. Supp.2d 1132, 1137 (D. Haw. 2011) (“These are not facts that are subject to common knowledge − Plaintiff needs medical evidence to substantiate these allegations.”); Windward Aviation, Inc. v. Rolls-Royce Corp., 2011 WL 2670180, at *21 (D. Haw. July 6, 2011) (“res ipsa loquitur is inapplicable to the complex technical causation issues in this case, for which Plaintiffs have offered no expert testimony in opposition”).

Idaho

Expert opinion is mandatory in Idaho litigation where “the causative factors are not ordinarily within the knowledge or experience of laymen composing the jury.”  Easterling v. Kendall, 367 P.3d 1214, 1226 (Idaho 2016).  “[M]atters [that] are scientific or far removed from the usual and ordinary experience of the average person . . . require expert knowledge.”  Kolln v. Saint Luke’s Regional Medical Center, 940 P.2d 1142, 1149 (Idaho 1997).  “[A] lay person cannot arrive at a decision as to causation without the benefit of an expert.”  Id. at 1228.

[W]here the subject matter regarding the cause of disease, injury, or death of a person is wholly scientific or so far removed from the usual and ordinary experience of the average person that expert knowledge is essential to the formation of an intelligent opinion, only an expert can competently give opinion evidence as to the cause of death, disease or physical condition.

Holdaway v. Broulim’s Supermarket, 349 P.3d 1197, 1203 (2015) (citation and quotation marks omitted).  A “permanent . . . condition as it exists months or years after the [incident] requires expert testimony to establish causation.”  Dodge-Farrar v. American Cleaning Services Co., 54 P.3d 954, 959 (Idaho App. 2002).

Thus, “[w]hether or not the [drug] taken by [plaintiff] was a cause of his [condition] is a matter of science that is far removed from the usual and ordinary experience of the average person.”  Swallow v. Emergency Medicine of Idaho, P.A., 67 P.3d 68, 77 (Idaho 2003).  Similarly,“in a toxic tort case . . . the issue of causation is framed by the expert opinions of scientists and treating physicians.”  Earl v. Cryovac, 772 P.2d 725, 728 (Idaho App. 1989).  See McGiboney v. CCA Western Properties, Inc., 2016 WL 843253, at *8 (D. Idaho March 1, 2016) (“complex questions of medical causation require expert testimony”); Sabo v. Fiskars Brands, Inc., 2014 WL 4365319, at *16 (D. Idaho Sept. 2, 2014) (“If the complexity of the causation issue is beyond common experience, expert testimony is required to establish causation.”) (citation and quotation marks omitted).

Illinois

Illinois law holds:

Without question, the human body is complex.  In most cases, the connection between the parts of the body and past and current injuries is a subject that is beyond the ken of the average layperson.  Because of this complexity, we do not believe that, in normal circumstances, a lay juror can effectively or accurately assess the relationship between a prior injury and a current injury without expert assistance.

Peach v. McGovern, ___ N.E.3d ___, 2019 WL 324608, at *5 (Ill. Jan. 25, 2019) (quoting Voykin v. Estate of DeBoer, 733 N.E.2d 1275, 1280 (Ill. 2000)).  Thus, “a plaintiff in a personal injury case must present the testimony of a medical expert to establish causation if the relationship between the claimed injury and the event in question requires special knowledge and training to establish.”  Brown v. Baker, 672 N.E.2d 69, 71 (Ill. App. 1996).  “[L]ay views about the origins of these medically complex problems do not suffice.”  Joyce v. J.C. Penney Corp., 389 F. Appx. 529, 531 (7th Cir. 2010) (applying Illinois law).

Numerous Illinois decisions have followed this rule in product liability and toxic tort cases.

[P]roduct liability cases are analogous to those involving medical malpractice:  Both types of cases involve specialized knowledge that bear directly on the standard of care in the community. . . .  [E]xpert opinion usually is required to aid the jury in determining that the pertinent standard of care has been breached.

Baltus v. Weaver Division, 557 N.E.2d 580, 589 (Ill. App. 1990).  See Clark v. River Metals Recycling, LLC, 929 F.3d 434, 441 (7th Cir. 2019) (“under Illinois law, [plaintiff] needed expert testimony to pin down exactly why the machine was designed in a defective way”) (applying Illinois law); Show v. Ford Motor Co., 659 F.3d 584, 585 (7th Cir. 2011) (“expert testimony is vital in design-defect suits when aspects of a product’s design or operation are outside the scope of lay knowledge”) (applying Illinois law); Korte v. Exxonmobil Coal USA, Inc., 164 F. Appx. 553, 556 (7th Cir. 2006) (“Expert testimony is needed to establish causation in cases alleging an adverse health effect when the medical effects of exposure to the toxin are not within the ken of the ordinary person.”) (applying Illinois law);  Fuesting v. Zimmer, Inc., 421 F.3d 528, 537 (7th Cir. 2005) (“In the absence of such [expert] evidence, [plaintiff] cannot establish the requisite elements of his claim.”), vacated in part on other grounds, 448 F.3d 936 (7th Cir. 2006) (remedy) (applying Illinois law); Wintz v. Northrop Corp., 110 F.3d 508, 515 (7th Cir. 1997) (“Under Illinois law, to serve as [evidence of] the proximate cause of the plaintiff’s injury, an expert must be able to testify with a reasonable degree of medical certainty that proximate cause existed.”) (applying Illinois law); Henry v. Panasonic Factory Automation Co., 917 N.E.2d 1086, 1091 (Ill. App. 2009) (“plaintiffs cannot establish a breach of the standard of care in this case without expert testimony”); Kane v. Motorola, Inc., 779 N.E.2d 302, 310 (Ill. App. 2002) (“plaintiffs . . . must come forward with scientific evidence regarding causation to preclude the entry of summary judgment”); Northern Trust Co. v. Upjohn Co., 572 N.E.2d 1030, 1036 (Ill. App. 1991) (“expert testimony shall be necessary . . . in a case, such as the one at bar, where a drug manufacturer’s liability for a prescription drug is based upon its failure to provide adequate warnings”); In re Depakote, 2017 WL 5483607, at *2 (S.D. Ill. Nov. 15, 2017) (“Expert testimony is necessary to establish proximate causation in cases where a drug manufacturer has failed to provide adequate warnings.”); In re Trasylol Products Liability Litigation, 2010 WL 8354662, at *18 (S.D. Fla. Nov. 23, 2010) (“Under Illinois law, where special medical knowledge is required, Plaintiff must present expert medical testimony to establish causation.”) (applying Illinois law); Lewis v. PDV America, Inc., 532 F. Supp.2d 1006, 1010-11 (N. D. Ill 2008) (lack of expert causation testimony fatal to plaintiff’s case and warrants summary judgment); Wroble v. Lockformer Co., 2006 WL 695254, at *1 (N.D. Ill. March 17, 2006) (“a plaintiff must establish proximate cause in a personal injury action through the admissible testimony of an expert witness”); Muller v. Synthes Corp., 2002 WL 460827, at *6 (N.D. Ill. March 26, 2002) (issue of “the design parameters of a medical implant . . . is one that goes beyond the knowledge that the average lay person reasonably could be expected to possess.  Accordingly, competent proof on this issue requires expert testimony.”).

Indiana

Under Indiana law, “expert testimony is required where the question involves medical factors beyond the common knowledge of the layman.”  Willis v. Westerfield, 839 N.E.2d 1179, 1188 (Ind. 2006).  “Indiana law makes clear that “questions of medical causation of a particular injury are questions of science necessarily dependent on the testimony of physicians and surgeons learned in such matters.”  Higgins v. Koch Development Corp., 794 F.3d 697, 703 (7th Cir. 2015) (quoting Armstrong v. Cerestar USA, Inc., 775 N.E.2d 360, 366 (Ind. App. 2002)) (applying Indiana law).

[W]hen there is no obvious origin to an injury and it has multiple potential etiologies, expert testimony is necessary to establish causation. . . .  Without an expert, a plaintiff in such a complex case would be free . . . to prove his allegations relying on the logical fallacy “post hoc ergo propter hoc”. . . .  [W]e conclude that a causation expert is required in this case.

Id., 794 F.3d at 703 (citations and quotation marks omitted).

Thus, where “the question of the causal connection . . . is a complicated medical question . . ., testimony of an expert witness on the issue is necessary.”  Daub v. Daub, 629 N.E.2d 873, 877 (Ind. App. 1994).  See Timm v. Goodyear Dunlop Tires North America, Ltd., ___ F.3d ___,  2019 WL 3559049, at *3 (7th Cir. Aug. 6, 2019) (“Indiana law required expert testimony here because distinguishing expected from enhanced injuries was an inquiry beyond the understanding of lay jurors”) (applying Indiana law); C.W. v. Textron, Inc., 807 F.3d 827, 838 (7th Cir. 2015) (“With no experts to prove causation − be it general or specific − the appellants cannot prove their toxic-tort case under Indiana law.”) (applying Indiana law); Piltch v. Ford Motor Co., 778 F.3d 628, 634 (7th Cir. 2015) (plaintiffs “cannot establish the existence of a defect without expert testimony”) (applying Indiana law); Ervin v. Johnson & Johnson, Inc., 492 F.3d 901, 905 (7th Cir. 2007) (“In the absence of any other expert evidence supporting [plaintiff’s] causation theory, the district court properly granted summary judgment.”).  See Armstrong v. Cerestar USA, Inc., 775 N.E.2d 360, 366 (Ind. App. 2002) (“questions of medical causation of a particular injury are questions of science necessarily dependent on the testimony of physicians and surgeons learned in such matters”) (quoting Hannan v. Pest Control Services, 734 N.E.2d 674, 679 (Ind. App. 2000)).

The same is true in prescription medical product cases.  “[W]hen the issue involves the complex internal medicine question of what caused a person’s symptoms when a drug is involved, that is a matter requiring expert opinion to connect the dots.”  Allen v. Hook-SupeRx, LLC, 2015 WL 1757086, at *3 (N.D. Ind. April 17, 2015).

Under Indiana law questions of medical causation of a particular injury are questions of science necessarily dependent on the testimony of physicians and surgeons learned in such matters.  When there is no obvious origin to an injury and it has multiple potential etiologies, expert testimony is necessary to establish causation.

Robinson v. Davol, Inc., 913 F.3d 690, 695 (7th Cir. 2019) (citations and quotation marks omitted) (applying Indiana law).

A mere temporal relationship between [Plaintiff’s] ingestion of [a drug] and his subsequent injury cannot form the basis for a reasonable finding of causation. . . .  Any finding of the fact of causation based solely on facts within the understanding of lay jurors would be bald speculation.  Therefore, this matter presents a situation where expert testimony is not only helpful but absolutely necessary.  When the issue of proximate cause is not within the understanding of lay persons, testimony of an expert witness on the issue is necessary. Questions of medical causation of a particular injury are questions of science necessarily dependent on the testimony of physicians and surgeons learned in such matters.

Porter v. Whitehall Laboratory, Inc., 791 F. Supp. 1335, 1341-42 (S.D. Ind. 1992) (citations and quotation marks omitted), aff’d, 9 F.3d 607, 612 (7th Cir. 1993) (“[w]e agree with the district court that expert testimony is necessary”).  See Dalton v. Teva North America, 891 F.3d 687, 692 (7th Cir. 2018) (“the issue of causation in [plaintiff’s] case is not obvious . . . therefore . . . [plaintiff] could not prove her tort claims without expert testimony”) (applying Indiana law); Bowersock v. Davol, Inc., 236 F. Supp.3d 1074, 1089 (S.D. Ind. 2017) (summary judgment granted on causation in medical device case after all plaintiff’s experts excluded), aff’d, 913 F.3d 690 (7th Cir. 2019); Tucker v. SmithKline Beecham Corp., 701 F. Supp.2d 1040, 1047 (S.D. Ind. 2010) (“Causation is a required element of each of the plaintiff’s claims, and, in pharmaceutical cases, expert testimony is required to prove a causal connection between the drug and its alleged effects.”); Minisan v. Danek Medical, Inc., 79 F. Supp.2d 970, 975 (N.D. Ind. 1999) (“[p]roof of legal causation in a medical device case must be by expert testimony”).

Iowa

Iowa law establishes that “medical causation . . . is essentially within the domain of expert testimony.”  Dunlavey v. Economy Fire & Casualty Co., 526 N.W.2d 845, 853 (Iowa 1995).  “[H]ighly technical questions of diagnoses and causation which lie beyond the understanding of a layperson require introduction of expert testimony.”  Donovan v. State, 445 N.W.2d 763, 766 (Iowa 1989).  “[M]edical testimony regarding whether an accident caused an injury is not within the knowledge and experience of ordinary layperson.”  Yates v. Iowa West Racing Ass’n, 721 N.W.2d 762, 774 (Iowa 2006).  “[U]nder Iowa law, due to its complex and scientific nature, medical causation almost always requires expert testimony.”  Vanderberg v. Petco Animal Supplies Stores, Inc., 906 F.3d 698, 707 (8th Cir. 2018)  (citation and quotation marks omitted) (applying Iowa law).  “[I]n toxic tort cases, ‘expert medical and toxicological testimony is unquestionably required to assist the jury’ in determining general and specific causation.”  Kinseth v. Weil-McLain, 913 N.W.2d 55, 69 (Iowa 2018) (quoting Ranes v. Adams Laboratories, Inc., 778 N.W.2d 677, 688 (Iowa 2010)).

The same rule applies in product liability litigation.  “In proving both types [general and specific] of causation, expert medical and toxicological testimony is unquestionably required to assist the jury.”  Junk v. Terminix International Co., 628 F.3d 439, 450 (8th Cir. 2010) (following Ranes) (applying Iowa law).  “In cases involving complicated technical and scientific issues expert testimony is required to submit the issue of a product defect under Iowa law.”  Iowa Great Lakes Sanitary District v. Travelers Casualty & Surety Co., 913 F.3d 760, 763 (8th Cir. 2019) (citation and quotation marks omitted) (applying Iowa law).  An “expert witness testimony opining that [the product] was a likely cause of [the injury is] a crucial element in products liability claims.”  Doe v. Baxter Healthcare Corp., 178 F. Supp.2d 1003, 1017 (S.D. Iowa 2001), aff’d, 380 F.3d 399 (8th Cir. 2004).  “Any decision which pertains to the design of the [medical] device involves engineering, metallurgical and medical principles beyond common knowledge and experience.”  Benedict v. Zimmer, Inc., 405 F. Supp.2d 1026, 1033 (N.D. Iowa 2005).  Questions concerning alternative designs “cannot be fully understood by the average juror without some expert assistance.”  Id. (citation omitted).  Similarly, “to show the device was defective because of inadequate instructions or warnings requires expert testimony.”  Id.  Likewise:

the element of causation . . . requires the presentation of expert evidence.  The court concludes the [plaintiffs] must present some expert testimony to prove the complex medical device caused [the] injuries. Causation in this case is a complex medical issue that is beyond common knowledge and experience.

Id. at 1033-34 (citations omitted).  See James v. Swiss Valley AG Service, 449 N.W.2d 886, 890 (Iowa App. 1989) (“when technical issues are involved (issues beyond common knowledge and experience) in a products liability or a products-related case, expert testimony is required to generate a jury issue”) (citation omitted); Rock v. Smith, 985 F. Supp.2d 1066, 1072 (S.D. Iowa 2013) (“Establishing liability for failure to instruct or warn also requires a plaintiff to establish that the lack of instructions or warnings caused the plaintiff harm.”) (citation omitted); Neilson v. Whirlpool Corp., 2012 WL 13018693, at *9 (S.D. Iowa Jan. 3, 2012) (“this products liability action contains issues that are beyond the understanding of the average juror and, therefore, expert testimony is required”); Korte v. Mead Johnson & Co., 824 F. Supp.2d 877, 887 (S.D. Iowa 2010) (“Plaintiffs must use the testimony of medical experts to prove medical causation”); Cummings v. Deere & Co., 589 F. Supp.2d 1108, 1118 (S.D. Iowa 2008) (“the present action involves complicated technical and scientific issues such that expert testimony is required to submit the issue of a product defect to a jury under Iowa law”) (footnote omitted); Housley v. Orteck International, Inc., 488 F. Supp.2d 819, 829 (S.D. Iowa 2007) (“The design, manufacture, use, and installation of [the product] is a matter largely outside the experiences of the average juror,” therefore “expert testimony is required”).

Kansas

“[T]he well-established test” in Kansas “for determining whether expert testimony is required is whether the subject matter is too complex to fall within the common knowledge of the jury and is beyond the capability of a lay person to decide.”  Williamson v. Amrani, 152 P.3d 60, 72 (Kan. 2007) (superseded by statute on other grounds). “Expert testimony is necessary where normal experience and qualifications of lay persons serving as jurors does not permit them to draw proper conclusions from the facts and circumstances of the case.”  Pope v. Ransdell, 833 P.2d 965, 973 (Kan. 1992).  Accord Hare v. Wendler, 949 P.2d 1141, 1148 (Kan. 1997) (quoted in Williamson).

The expert requirement has been repeatedly applied in Kansas product liability cases.  See Ralston v. Smith & Nephew Richards, Inc., 275 F.3d 965, 974 (10th Cir. 2001) (“[w]ithout the expert testimony . . ., we can discern no material issue of fact with regard to the adequacy of the warnings provided by [the medical device manufacturer]”) (applying Kansas law); Robison Farms, Inc. v. ADM Alliance Nutrition, Inc., 2007 WL 2875132, at *19 (D. Kan. Sept. 29, 2007) (where “the facts involve such technical complexities that they exceed the experience and understanding of the average layman . . . without the aid of expert testimony, a reasonable trier of fact could not determine the cause of the harm”) (citation, footnote, and quotation marks omitted); Vanderwerf v. SmithKlineBeecham Corp., 529 F. Supp.2d 1294, 1306 (D. Kan. 2008) (“plaintiffs cannot meet their burden of proving medical causation without expert testimony that [the drug] can cause [plaintiff’s injury]”); Miller v. Pfizer, Inc., 196 F. Supp.2d 1095, 1125 (D. Kan. 2002) (“Because plaintiffs have no scientific evidence of general causation, their claim of failure to warn must fail as a matter of law.”), aff’d, 356 F.3d 1326 (10th Cir. 2004); Smith v. Pfizer Inc., 2001 WL 968369, at *12 (D. Kan. Aug. 14, 2001) (“plaintiff cannot establish general causation, inadequate testing, or inadequate warning because she has no expert through whom to present evidence that a causal relationship or an association exists”).

Kentucky

In Kentucky courtrooms, “[i]t is an accepted principle that in most medical negligence cases, proof of causation requires the testimony of an expert witness because the nature of the inquiry is such that jurors are not competent to draw their own conclusions from the evidence without the aid of such expert testimony.”  Baylis v. Lourdes Hospital, Inc., 805 S.W.2d 122, 124 (Ky. 1991) (citations and footnote omitted).  “[T]he human body is perhaps the most complex system known to humankind, so . . . this is exactly why our legal system requires reliable expert proof on issues such as medical causation.”  Kingery v. Sumitomo Electric Wiring, 481 S.W.3d 492, 499 (Ky. 2015).  Thus, “[e]xperts are often required in complex cases in which a jury will not understand, through common knowledge or experience, the intricacies involved in the negligence claim.”  Caniff v. CSX Transportation, Inc., 438 S.W.3d 368, 374 (Ky. 2014).

Likewise, “expert testimony is required in a products liability case . . . when the subject presented is so distinctly related to an area that is so far removed from the grasp of the average lay person.”  Stevens v. Keller Ladders, 1 F. Appx. 452, 458 (6th Cir. 2001) (applying Kentucky law).

As a general rule, expert witnesses are generally necessary, indeed essential, in products liability cases, as they are in medical malpractice actions, to prove such matters as a product defect and proximate causation, unless of course the nature of the defect and resultant injuries are so obvious as to fall within the general knowledge of the ordinary person.

Thomas v. Manchester Tank & Equipment Corp., 2005 WL 3673118, at *1 (W.D. Ky. May 13, 2005) (citation and quotation marks omitted).

[E]xpert testimony is necessary to support the element of causation in a negligence action when the common knowledge or experience of lay persons cannot recognize or infer a causal connection between the alleged negligence and the injury.  Courts have held that personal injury cases arising out of exposure to drugs involve complex questions of medical causation beyond the understanding of a lay person, and these require expert testimony on causation issues.

Hans v. Matrixx Initiatives, Inc., 2007 WL 2668594, at *3 (W.D. Ky. Sept. 6, 2007) (citations omitted).  See Hill v. Express Tan, Inc., 2019 WL 1757534, at *3 (W.D. Ky. April 19, 2019) (“Without expert testimony on any defect related to the tanning bed, the jury would be left to speculate.”) (citation and quotation marks omitted); Sturgeon v. Johnson & Johnson, 2017 WL 4080686, at *2 (E.D. Ky. Sept. 14, 2017) (summary judgment appropriate against expert-less plaintiff because “[t]he nature of any defect in the [medical device] is not something that falls within the general knowledge of ordinary people”); Wells v. Wal-Mart Stores Inc., 2016 WL 1453912, at *1 (E.D. Ky. April 13, 2016) (“Expert witnesses are ‘generally necessary’ in a Kentucky products liability case to prove the presence of a defect.”); Earle v. United States, 2016 WL 8814363, at *6 (Mag. E.D. Ky. Feb. 8, 2016) (“Laypeople certainly are not competent, based on common, everyday experience, to judge relative injury causation or delay effect as to a highly complex area of the body.”), adopted, 2016 WL 1417811, at *5 (E.D. Ky. April 11, 2016); Hinken v. Sears Roebuck & Co., 2015 WL 165027, at *4 (E.D. Ky. Jan. 13, 2015) (following Thomas and Watson; granting summary judgment); Trent v. Ford Motor Co., 2 F. Supp.3d 1022, 1027 (W.D. Ky. 2014) (plaintiff’s “design defect claim turns on specialized knowledge that cannot be determined intelligently from testimony on the basis of ordinary knowledge gained in the ordinary affairs of life.”) (citation and quotation marks omitted); Fimbres v. Garlock Equipment Co., 2014 WL 2612513, at *8 (W.D. Ky. June 11, 2014) (“Without the benefit of expert testimony on this issue, Plaintiff cannot meet her burden of producing evidence of the inadequacy of [defendant’s] warnings.”); Burgett v. Troy-Bilt LLC, 970 F. Supp.2d 676, 683 (E.D. Ky. 2013) (plaintiffs’ “attempt to establish causation would crumble for another reason: they need an expert witness”), aff’d, 579 F. Appx. 372 (6th Cir. 2014); Adams v. Cooper Industries, Inc., 2012 WL 2339741, at *1 (E.D. Ky. June 19, 2012) (“Both elements of causation require scientific assessments that must be established through expert testimony.”); Jeffrey v. Taylor, 2012 WL 694030, at *5 (W.D. Ky. March 1, 2012) (“the complicated nature of the issues of medical causation and damages require expert testimony and not merely Plaintiff’s lay opinion”); Dailey v. Hoffman/New Yorker, Inc., 2011 WL 5598908, at *3 (E.D. Ky. Nov. 17, 2011) (the product “is a technical piece of equipment and expert testimony is required not only to explain the various possible explanations for the accident, including any design and manufacturing defects, but also to opine about the probable cause of the accident”); Freytes v. Wal-Mart Stores East, LP, 2011 WL 2119383, at *4 (E.D. Ky. May 26, 2011) (“expert testimony establishing a connection between the [product] and [plaintiff’s] injuries is likely necessary”; plaintiff “simply asks the jury to speculate and surmise too much”); May v. Ford Motor Co., 2010 WL 5391605, at *2 (E.D. Ky. Dec. 22, 2010) (following Thomas; granting summary judgment); Watson v. Ford Motor Co., 2009 WL 5064316, *3 (E.D .Ky. Dec. 15, 2009) (“Expert witnesses are generally necessary, indeed essential, in products liability cases, as they are in medical malpractice actions, to prove such matters as a product defect and proximate causation.”); Snyder v. American Honda Motor Co., 2009 WL 2342733, at *7 (E.D. Ky. July 28, 2009) (“Kentucky law requires Plaintiffs to present expert testimony demonstrating that Defendants’ product was defective because the subject matter falls outside the general knowledge of the ordinary person”); Honaker v. Innova, Inc., 2007 WL 1217744, at *2 (W.D. Ky. April 23, 2007) (“Expert testimony is almost always needed to meet the plaintiff’s burden in a products liability case.”).

Louisiana

For once, Louisiana law is not peculiar, holding that “only a physician or other qualified expert is capable of judging what [medical] risk exists and the likelihood of occurrence.”  Snider v. Louisiana Medical Mutual Insurance Co., 130 So.3d 922, 930 (La. 2013).

[W]e find the plaintiff was required to produce evidence from a medical expert to establish a breach of the standard of care, as well as causation. . . .  Here, the plaintiff was required to present medical evidence to establish the defendant’s actions fell below the standard of care and caused her injuries.  Without this evidence, the plaintiff has, in our view, failed to show that she will be able to carry her burden of proof at trial. . . .  We conclude the plaintiff . . . was required to produce expert medical evidence sufficient to establish that she will be able to satisfy her evidentiary burden of proof at trial.

Schultz v. Guoth, 57 So.3d 1002, 1009-10 (La. 2011) (citations omitted).  “[O]ur long standing jurisprudence has held, because of the complex medical and factual issues involved, a plaintiff will likely fail to sustain his burden of proving his claim . . . without medical experts.”  Khammash v. Clark, 145 So.3d 246, 259 (La. 2014) (citations and quotation marks omitted).  See Madere v. Collins, 241 So.3d 1143, 1149 (La. App. 2018) (“complex surgical and medical actions . . . require expert evidence of the applicable standard of care and expert testimony regarding negligence and causation”).

The same is true in product liability and toxic tort actions. (“When a conclusion regarding medical causation is not one within common knowledge, expert medical testimony is required in a tort action.”  Johnson v. E.I. DuPont de Nemours & Co., 7 So.3d 734, 740 (La. App. 2009).  “[T]o conclude that a different [design] or a different warning would have” changed the outcome in a product liability action,

therefore raises questions that are of sufficient complexity to be beyond the expertise of the average judge and juror and that common sense does not make obvious.  Accordingly, [plaintiffs] were required to provide the jury with expert testimony related to causation.

Stewart v. Capital Safety USA, 867 F.3d 517, 521-22 (5th Cir. 2017) (applying Louisiana law).  See Boudreaux v. Bollinger Shipyard, 197 So.3d 761, 775 (La. App. 2016) (“expert medical testimony is required when the conclusion regarding medical causation is one that is not within common knowledge”); Bourgeois v. Garrard Chevrolet, Inc., 811 So.2d 962, 967 (La. App. 2002) (“Without expert testimony, the plaintiff cannot carry his burden of proof that the [product] was defective in design or that an alternative design would have prevented the plaintiff’s injuries”); Hutchinson v. Shah, 648 So.2d 451, 452 (La. App. 1994) (“When the conclusion regarding medical causation is not one within common knowledge, expert medical testimony is required.”); Winstead v. Georgia Gulf Corp., 77 F. Appx. 267, 271 (5th Cir. 2003) (plaintiff “was required to present expert testimony because the cause of [a] chemical release is beyond the understanding of an untrained lay person”) (applying Louisiana law); Barber v. Spinal Elements, 2019 WL 3554200, at *4 (E.D. La. Aug. 5, 2019) (“courts consistently require expert testimony in products liability cases, when the product or feature in question is complex, and a layman may not readily grasp the implications”); Talbot v. Electric Insurance Co., 2018 WL 6274314, at *3 (M.D. La. Nov. 30, 2018) (“as a matter of law, non-expert testimony by a fact witness is insufficient to establish medical causation”); Patton v. Boston Scientific Corp., 2018 WL 4760846, at *2 (W.D. La. Oct. 2, 2018) (“in tort actions involving complex medical devices and concepts, medical causation cannot be established without the aid of expert medical testimony”); Williams v. Janssen Pharmaceuticals, 2016 WL 6127526, at *2 (W.D. La. Oct. 20, 2016) (“A plaintiff must have expert medical testimony to prove causation in a product liability claim involving prescription medications.”); Hooks v. Nationwide Housing Systems, LLC, 2016 WL 3667134, at *13 (E.D. La. July 11, 2016) (“In a toxic tort case, the plaintiff must present admissible expert testimony to establish general causation as well as specific causation. Konrick v. Exxon Mobil Corp., 2016 WL 430404, at *2 (E.D. La. Feb. 4, 2016) (“In a toxic tort suit, the plaintiff must present admissible expert testimony to establish general causation and specific causation”); Underwood v. General Motors LLC, 2015 WL 5475610, at *3 (M.D. La. Sept. 17, 2015) (“it is not possible for a jury to determine a product to be defective . . . without expert testimony”), aff’d, 642 F. Appx. 468 (5th Cir. 2016); Burst v. Shell Oil Co., 2014 WL 3893304, at *2 (E.D. La. Aug. 8, 2014) (“expert medical testimony is required to resolve the issue of general causation”); Demouchet v. General Nutrition Corp., 2014 WL 1652518, at *4 (W.D. La. April 24, 2014) (“In cases such as this, involving complex issues of medical causation that are beyond the realm of knowledge and experience of the ordinary juror, expert testimony must be presented by the plaintiff to prove specific causation.”); Sadler v. International Paper Co., 2014 WL 1217954, at *3 (W.D. La. March 24, 2014) (“A plaintiff in a toxic tort case must establish medical causation through expert testimony.”); Pratt v. Landings at Barksdale, 2013 WL 5376021, at *3 (W.D. La. Sept. 24, 2013) (“In a toxic tort suit, the plaintiff must present admissible expert testimony to establish general causation as well as specific causation.”) (citation and quotation marks omitted); Rhodes v. Bayer Healthcare Pharmaceuticals, Inc., 2013 WL 1282450, at *2 (W.D. La. March 28, 2013) (“lack of an expert to establish causation is fatal to Plaintiffs’ claims”); Autery v. SmithKline Beecham Corp., 2011 WL 1812793, at *6 (Mag. W.D. La. April 12, 2011) (“courts routinely dismiss product liability cases in which expert testimony on causation is lacking”), adopted, 2011 WL 1828343 (W.D. La. May 12, 2011), aff’d, 496 F. Appx. 388 (5th Cir. 2012); Horton v. Wyeth Pharmaceuticals, 2010 WL 11607305, at *3 (W.D. La. May 27, 2010) (“summary judgment is appropriate on the independent ground that [plaintiffs] have failed to identify an expert witness or submit an expert report.  Such failure is fatal to their prescription drug product liability action, as expert medical testimony is required”); Smith v. Glaxosmithkline Corp., 2008 WL 4938426, at *2 (E.D. La. Nov. 17, 2008) (“Plaintiffs can only establish the required elements of causation between [the drug] and [decedent’s] death through expert testimony”); Waters v. Bayer Corp., 2006 WL 725820, at *2 (W.D. La. March 22, 2006) (“In a case such as this, involving complex medical issues not commonly known to the average person, the courts have held that expert medical testimony must be offered to prove causation.”); Kemp v. Metabolife International, Inc., 2004 WL 2095618, at *3 (E.D. La. Sept. 13, 2004) (“proof of actual causation requires medical testimony”).

Maine

Under Maine law, “[a]llowing a jury to infer causation on complex medical facts without the aid of expert testimony on the subject . . . stretches the jury’s role beyond its capacity.”  Merriam v. Wanger, 757 A.2d 778, 782 (Me. 2000).  Where a case “concerns such technical and involved medical procedure that it rules out any possibility of understanding on the part of a layman as to its medical nature” it falls within “the general rule [requiring] expert medical testimony.”  Cyr v. Giesen, 108 A.2d 316, 318 (Me. 1954).

[T]he identification of a cause for serious medical conditions . . . − let alone prospective injuries that have not yet developed − is neither a lay exercise” nor “a matter within common, non-expert understanding.  Rather, the causal relationship . . . draws on sophisticated science beyond the ken of the average juror.  Accordingly, a jury may not infer causation on complex medical facts without the aid of expert testimony.

Darney v. Dragon Products Co., LLC, 640 F. Supp.2d 117, 123 (D. Me. 2009) (citations, quotation marks, and footnote omitted).  See Samaan v. St. Joseph Hospital, 670 F.3d 21, 38 (1st. Cir. 2012) (“Given the complex medical question that underlies the issue of causation in this instance, expert testimony was essential.”) (applying Maine law); Rollins v. Wentworth, 2013 WL 3781504, at *7 (D. Me. 2013) (“with a plaintiff having as complex a medical history as [plaintiff], it would be necessary to produce expert testimony from a qualified medical expert”); Kalis v. Strang, 2005 WL 2715239, at *4 (Me. Super. May 9, 2005) (“because plaintiff never named an expert, he will be unable to link his symptoms to the [accident]”).

Maritime

The rule in maritime cases is that “[e]xpert testimony is required whenever proof of an element of a claim, such as the duty of care or causation, calls for information that is outside an ordinary person’s common knowledge.”  Rhodes v. Energy Marine LLC, 2016 WL 6700973, at *3 (D. Ariz. Nov. 15, 2016) (applying maritime law).

Where, however, the nexus between the injury and the alleged cause would not be obvious to the lay juror, expert evidence is often required to establish the causal connection between the accident and some item of physical or mental injury.  In a case such as this, where an injury has multiple potential etiologies, expert testimony is necessary to establish causation, even in view of plaintiff’s reduced burden to prove causation.

Wills v. Amerada Hess Corp., 379 F.3d 32, 46 (2d Cir. 2004) (citations and quotation marks omitted) (Sotomayor, J.) (applying maritime law).  See Seaman v. Seacor Marine L.L.C., 326 F. Appx. 721, 729 (5th Cir. 2009) (in toxic exposure case, with expert testimony excluded, plaintiff “lacks competent summary judgment evidence that would create a genuine fact issue regarding . . . causation”) (applying maritime law); Gauthreaux v. United States, 694 F. Supp.2d 460, 465 (E.D. Va. 2009) (“in a products liability action, proof of causation must ordinarily be supported by expert testimony because of the complexity of the causation facts”) (applying maritime law); Holman v. Applied Drilling Technology, Inc., 2007 WL 1577660, at *3 (S.D. Tex. May 31, 2007) (“Expert testimony is particularly necessary in chemical-exposure cases, in which medically complex diseases and causal ambiguities compound the need for expert testimony.”) (citation and quotation marks omitted) (applying maritime law).

Maryland

The Maryland Court of Appeals has held that, “lay jurors would not be permitted to draw an inference of negligence without the aid of expert testimony” where a case presents an “issue” of a “complex and technical nature.”  Holzhauer v. Saks & Co., 697 A.2d 89, 96 (Md. 1997).

This is not an “obvious injury” case.  Resolution of the issues of negligence and causation involved in a case of this kind necessarily requires knowledge of complicated matters, including human anatomy, medical science, operative procedures, areas of patient responsibility, and standards of care.  Complex issues of the type generated by a case of this kind should not be resolved by laymen without expert assistance.

Orkin v. Holy Cross Hospital, Inc., 569 A.2d 207, 209 (1990).  “[W]here the cause of an [injury] claimed to have resulted from a negligent act is a complicated medical question involving fact finding which properly falls within the province of medical experts. . ., proof of the cause must be made by such witnesses.”  Wilhelm v. State Traffic Safety Commission, 185 A.2d 715, 719 (Md. 1962) (citations omitted).  See Levitas v. Christian, 164 A.3d 228, 230 (Md. 2017) (“the complex issues of causation in lead paint cases generally require expert testimony”); Aventis Pasteur, Inc. v. Skevofilax, 914 A.2d 113, 135 (Md. 2007) (“a medical expert on specific causation was necessary” because whether vaccines cause autism is “a complex medical question”); Miller v. Mandrin Homes, Ltd., 305 F. Appx. 976, 980 (4th Cir. 2009) (plaintiffs “produced no evidence of medical causation. . . .  The district court properly granted summary judgment.”) (applying Maryland law).

In product liability cases, it is also “well settled that expert testimony is required when the subject of the inference is so particularly related to some science or profession that it is beyond the ken of the average layman.”  Wood v. Toyota Motor Corp., 760 A.2d 315, 319 (Md. Spec. App. 2000) (citations and quotation marks omitted).  “Maryland courts have adopted the general rule that expert testimony is required when the subject of the inference that a product is defective is particularly related to some science or profession that it is beyond the ken of the average layman.”  Jones v. Reichert Jung, Inc., 211 F. Supp.2d 661, 667 (D. Md. 2002) (citing Wood).

[E]xpert testimony is usually necessary since the evidence relating to causation involves technical medical questions beyond the common knowledge of laypersons, and the interaction of a [medical device] with the human body raises technical questions requiring expert testimony.  Thus, if the plaintiff has failed to identify admissible evidence with respect to establishing that the [devices] were defective, and that such defect caused her injuries, then [defendant] is entitled to summary judgment, because each of the tort claims . . . depends upon plaintiff proving both defect, and causation.

Miskin v. Baxter Healthcare Corp., 107 F. Supp.2d 669, 672 (D. Md. 1999) (citations omitted), aff’d, 213 F.3d 632 (4th Cir. 2000) (affirmed “on the reasoning” of the court below).  See John Crane, Inc. v. Linkus, 988 A.2d 511, 522 (Md. App. 2010) (following Wood on causation); American Strategic Insurance Corp. v. Scope Services, Inc., 2017 WL 4098722, at *2 (D. Md. Sept. 15, 2017) (“It is well established under Maryland law that expert testimony is required when the subject of the inference is so particularly related to some science or profession that it is beyond the ken of the average laymen.”) (citation and quotation marks omitted); Osunde v. Lewis, 281 F.R.D. 250, 261 (D. Md. 2012) (“the notion that complicated issues of medical causation require expert testimony is well established in Maryland law”); Selective Insurance Co. v. Empire Comfort Systems, 2007 WL 7681251, at *4 (D. Md. March 21, 2007) (in claims “alleg[ing] the malfunction of complex machinery, expert testimony is required to establish negligence and causation”); Giddings v. Bristol-Myers Squibb Co., 192 F. Supp.2d 421, 423 (D. Md. 2002) (following Miskin); Markey v. Centocor, Inc., 2008 WL 6087370, at *8 (Md. Cir. April 29, 2008) (“Because this case involves numerous drug companies and a drug study . . ., whatever Plaintiffs theory of liability, it necessarily involves a complicated medical question. . . .  Without expert testimony, Plaintiff cannot proceed with her case and the entry of summary judgment in favor of [defendant] would be appropriate.”).

Massachusetts

Massachusetts recognizes that “[m]edical causation has two components, both of which require expert opinion evidence . . . general causation, i.e., that the drug can cause the injury, and specific causation, i.e., that the drug did cause the injury in this case.”  Reckis v. Johnson & Johnson, 28 N.E.3d 445, 461 n.33 (Mass. 2015).  Recognition that medical causation is “a matter beyond the common knowledge of the ordinary layman and proof of it must rest upon expert medical testimony” goes back decades.  Hachadourian’s Case, 162 N.E.2d 663, 666 (Mass. 1959).

The presence of such a defect cannot be inferred in the absence of expert testimony.  The opinion of the nonexperts who testified at trial cannot substitute for this absence of expert testimony.  Lacking expert testimony, other possible causes of the [accident] were not sufficiently eliminated.

Enrich v. Windmere Corp., 616 N.E.2d 1081, 1084 (Mass. 1993) (citations omitted).  “Because understanding medical causation is beyond the . . . knowledge of the ordinary layman . . . proof of it must rest upon expert medical testimony.”  Case of Canavan, 733 N.E.2d 1042, 1051 (Mass. 2000).  Summary judgment is “appropriate” where “[w]ithout the aid of an expert in the field, jurors would also be left to speculate about whether alternatively engineered designs might have prevented the accident.”  Esturban v. Massachusetts Bay Transportation Authority, 865 N.E.2d 834, 836 (Mass. App. 2007).  “[I]f the causation question involves questions of medical science or technology, the jury requires the assistance of expert testimony.”  Held v. Bail, 547 N.E.2d 336, 338 (Mass. App. 1989) (citations omitted).

In product liability cases:

It is also well-settled under Massachusetts law that understanding medical causation is a matter beyond the common knowledge of the ordinary layman and proof of it must rest upon expert medical testimony.  This applies to the requisite showings for both general and specific causation.  Without such expert testimony, a fact finder would have no basis other than conjecture, surmise, or speculation upon which to conclude that the injuries of which a plaintiff complains were caused by the impact of the Defendants’ product.

Jackson v. Johnson & Johnson, 330 F. Supp.3d 616, 625 (D. Mass. 2018) (citations and quotation marks omitted).  See Goffredo v. Mercedes-Benz Truck Co., 520 N.E.2d 1315, 1319 (Mass. 1988) (“[w]ithout the testimony of an expert . . ., the evidence was insufficient to establish that the design of the [product] was defective and that the defect caused” plaintiff’s injuries); Milward v. Rust-Oleum Corp., 820 F.3d 469, 476 (1st Cir. 2016) (“expert testimony is required to establish medical causation”; “This applies to both general and specific causation.”) (applying Massachusetts law); Hochen v. Bobst Group, Inc., 290 F.3d 446, 451 (1st Cir. 2002) (“here the nature of the defect or breach of warranty and its causal relation to the accident were complex and thus appropriately the subject of expert testimony”) (applying Massachusetts law); Carrozza v. CVS Pharmacy, Inc., ___ F. Supp.3d ___, 2019 WL 2913987, at *6 (D. Mass. July 8, 2019) (“in Massachusetts expert testimony is required on highly technical medical issues, including injury causation”) (citation and quotation marks omitted); Williams v. Techtronic Industries North America, Inc., 2014 WL 2865874, at *5 (D. Mass. June 23, 2014), (“In products liability cases, where the causal link between the alleged defect and the accident are beyond the ken of the jury, expert testimony is necessary to defeat summary judgment.”), aff’d, 600 F. Appx. 1 (1st Cir. 2015); Calisi v. Abbott Laboratories, 2013 WL 5441355, at *15 (D. Mass. Sept. 27, 2013) (“Under Massachusetts law, when the nature of the defect or breach of warranty and its causal relation to the [injury is] complex, a plaintiff must introduce expert testimony.”) (citations and quotation marks omitted); Carlucci v. CNH America LLC, 2012 WL 4094347, at *10 (D. Mass. Sept. 14, 2012) (“a plaintiff generally must provide expert testimony when the product is complex or technical such that it is beyond the common knowledge of the jury”); Kerlinsky v. Sandoz Inc., 783 F. Supp.2d 236, 242 (D. Mass. 2011) (“the issue of medical causation requires expert analysis”); Langadinos v. Hosokawa Micron International, Inc., 2011 WL 1213079, at *1 (D. Mass. March 31, 2011) (“given the nature of the injury and complexity of the relevant machinery, expert testimony is necessary to support plaintiff’s claims”); Pritchard v. Stanley Access Technologies, LLC, 2011 WL 309662, at *5 (D. Mass. Jan. 27, 2011) (“a jury could not reasonably conclude, on the basis of the evidence of record and in the absence of expert testimony, that Defendants’ negligence was more likely than not the cause of [plaintiff’s] alleged injuries”) (emphasis original); In re Neurontin Marketing & Sales Practices & Products Litigation, 2010 WL 3169485, at *2 (D. Mass. Aug. 10, 2010) (summary judgment granted where “plaintiff does not have an expert who will testify that [the drug] specifically caused her symptoms”); Morse v. Ford Motor Co., 2010 WL 2773527, at *1 (D. Mass. July 13, 2010) (“In cases involving claims of product defect (such as this case), expert testimony is required because the answers to the highly technical and specialized questions raised by such claims lie outside the knowledge of most lay jurors.”); Alves v. Mazda Motor of America, Inc., 448 F. Supp.2d 285, 301 (D. Mass. 2006) (“As expert evidence is essential to [plaintiff’s] case, the defendants are clearly entitled to prevail now that their evidence is being excluded.”); Polaino v. Bayer Corp., 122 F. Supp.2d 63, 71 (D. Mass. 2000) (“without such [expert] testimony, plaintiff can prove neither a design defect nor causation”).

Michigan

Michigan law has “long recognized the importance of expert testimony . . . to educate the jury and the court regarding matters not within their common purview.”  Locke v. Pachtman, 521 N.W.2d 786, 790 (Mich. 1994).  See Woodard v. Custer, 702 N.W.2d 522, 525 (Mich. 2005) (quoting and following Locke).  Likewise, determining causation in toxic tort cases is “scientific in nature . . . [so] it is to the scientific community that the law must look for the answer.  For this reason, expert witnesses are indispensable.”  Nelson v American Sterilizer Co., 566 N.W.2d 671 (Mich. App. 1996).  “[I]n toxic tort cases involving complex chemicals and their effects on human health, expert testimony is often required because the alleged injuries are not immediately obvious and the connection between exposure and injury is not a matter of common sense or everyday experience.”  Hendrian v. Safety-Kleen Systems, Inc., 2015 WL 4770966, at *4 (E.D. Mich. Aug. 13, 2015) (citation and quotation marks omitted).  See also Lowery v. Enbridge Energy Ltd. Partnership, 898 N.W.2d 906, 917-18 (Mich. 2017) (“expert testimony on causation is necessary in a toxic tort case when the legal proposition is beyond the common knowledge of an ordinary juror”) (Markman, C.J., concurring).

The same is true in product liability.

Plaintiffs have failed to proffer expert evidence . . . to support their contention that [the medical device] . . . caused [the] injuries in this case.  This requires the Court to grant Defendant’s motion for summary judgment. . . .  [E]xpert testimony is indispensable to prove causation where it is to the scientific community that the law must look for the answer.”

Avendt v. Covidien, Inc., 262 F. Supp.3d 493, 532 (E.D. Mich. 2017) (citations and quotation marks omitted).  See Swartz v. Procter & Gamble Manufacturing Co., 2018 WL 2239558, at *5 (E.D. Mich. May 16, 2018) (“expert testimony is required to demonstrate the existence of a reasonable alternative design that would satisfy the elements of a plaintiff’s claim”); In re Dow Corning Corp., 541 B.R. 643, 654 (E.D. Mich. 2015) (“Both causation inquiries − general and specific − involve scientific assessments that must be established through the testimony of a medical expert.”), aff’d, 667 F. Appx. 538 (6th Cir. 2016); Eiben v. Gorilla Ladder Co., 2013 WL 1721677, at *16 (E.D. Mich. April 22, 2013 (“Because the expert’s testimony is inadmissible, . . . Plaintiff’s claim of design defect cannot survive summary judgment.”); Dow v. Rheem Manufacturing Co., 2011 WL 4484001, at *22 (E.D. Mich. Sept. 26, 2011) (“expert testimony on causation is necessary, where the claim presents technical issues that are beyond the common experience and understanding of the common juror.”) (citations and quotation marks omitted), aff’d, 527 F. Appx. 434 (6th Cir. 2013); Gillett v. Sofamor, S.N.C., 2001 WL 1135304, at *6 (E.D. Mich. Sept. 13, 2001) (without expert testimony “Plaintiff has not presented sufficient evidence to establish a prima facie case that an alternative design was available”); Berry v. Crown Equipment Corp., 108 F. Supp.2d 743, 756 (E.D. Mich. 2000) (“In the absence of expert testimony concerning reasonableness of the plaintiff’s proposed alternative design, a manufacturer is entitled to entry of judgment as a matter of law.”).

Minnesota

In Minnesota, “[e]xpert opinion is required to prove causation if the issue is outside the realm of common knowledge.”  Walton v. Jones, 286 N.W.2d 710, 715 (Minn. 1979).

It is well-settled law . . . that the need for positive expert testimony to establish a causal connection between the defendant’s negligent act and the plaintiff’s injury or condition depends upon the nature of the question.  Where the question involves obscure and abstruse medical factors such that the ordinary layman cannot reasonably possess well-founded knowledge of the matter and could only indulge in speculation in making a finding, there must be expert testimony, based on an adequate factual foundation, that the thing alleged to have caused the result not only might have done so, but in fact did cause it.

Stahlberg v. Moe, 166 N.W.2d 340, 345 (Minn. 1969) (citations omitted).  “Where a question involves obscure and abstruse medical factors such that the ordinary [lay person] cannot reasonably possess well-founded knowledge in the matter and could only indulge in speculation . . . there must be expert testimony.”  Gross v. Victoria Station Farms, Inc., 578 N.W.2d 757, 762 (Minn. 1998) (citation and quotation marks omitted).  Thus, “[e]xpert testimony is generally required” in cases that “involve complex scientific or technological issues.”  Mercer v. Andersen, 715 N.W.2d 114, 122 (Minn. App. 2006).

The rule in product liability is the same.  “[P]ersonal injury cases involving pharmaceuticals, toxins or medical devices involve complex questions of medical causation beyond the understanding of a lay person.”  In re Baycol Products Litigation, 321 F. Supp.2d 1118, 1126 (D. Minn. 2004).  “Under Minnesota law, expert testimony is required to prove causation in cases involving complex medical issues with which a jury is unlikely to have experience.”  In re Viagra Products Liability Litigation, 658 F. Supp.2d 950, 968 (D. Minn. 2009) (quoting Johnson v. Zimmer, Inc., 2004 WL 742038, at *6 (D. Minn. March 31, 2004)).  See Fireman’s Fund Insurance Co. v. Canon U.S.A., Inc., 394 F.3d 1054, 1060-61 (8th Cir. 2005) (“Absent the excluded opinions of the . . . experts, [plaintiff] presented no evidence of any defect in the [product].”) (applying Minnesota law); Polski v. Quigley Corp., 2007 WL 2580550, at *11 (D. Minn. Sept. 5, 2007) (“Because the Court will not permit [plaintiffs’ expert] to testify that [the product] caused [their] injuries, [plaintiffs] will not be able to establish causation at trial.”), aff’d, 538 F.3d 836 (8th Cir. 2008); Rye v. Matrixx Initiatives, Inc., 2007 WL 2475960, at *4 (D. Minn. Aug. 24, 2007) (also quoting Johnson); Willert v. Ortho Pharmaceutical Corp., 995 F. Supp. 979, 983 (D. Minn. 1998) (“the present case involves such obscure and abstruse medical questions requiring competent expert testimony”).

Mississippi

In Mississippi litigation, “[e]xpert testimony is required unless the matter in issue is within the common knowledge of laymen.”  Denham v. Holmes, 60 So.3d 773, 789 (Miss. 2011) (quoting Palmer v. Biloxi Regional Medical Center, Inc., 564 So.2d 1346, 1355 (Miss. 1990)). “ In all but the simple and routine cases, it is necessary to establish medical causation by expert testimony.”  Short v. Wilson Meat House, LLC, 36 So.3d 1247, 1253 (Miss. 2010) (citation and quotation marks omitted).  Thus, “Mississippi law requires expert medical testimony where causation is an issue in a complicated case because such determinations are generally outside the scope of the average experiences and qualifications of most lay jurors.”  Brown v. Eli Lilly & Co., 654 F.3d 347, 358 (2d Cir. 2011) (applying Mississippi law).

Similar holdings under Mississippi law have occurred in product liability and toxic tort cases.  See Savage v. Pilot Travel Centers, L.L.C., 464 F. Appx. 288, 290 (5th Cir. 2012) (“Under Mississippi law, actions involving ‘medically complicated’ injuries require expert testimony on causation.”) (applying Mississippi law); Hill v. Koppers, Inc., 2009 WL 4908836, at *7-8 (N.D. Miss. Dec. 11, 2009 (Daubert exclusion of plaintiff’s experts created a “complete failure of proof . . . on general and specific causation”); Berry v. Southwest Airlines Co., 2008 WL 3874368, at *3 (S.D. Miss. Aug. 15, 2008) (“with injuries that are medically complicated, as is the case here, expert testimony is required to prove causation”); Jackson v. Bayer Corp., 2007 WL 2580379, at *4 (S.D. Miss. Sept. 4, 2007) (applying Mississippi law) (plaintiffs “have not offered any expert proof at all . . . that [the drug] caused or contributed to the plaintiffs’ alleged injuries and damages.  Failure to offer evidence on a critical matter upon which they bear the burden is fatal to their case”).

Missouri

Under the law of Missouri, “[m]edical causation, which is not within common knowledge or experience, must be established by scientific or medical evidence showing the relationship between the complained of condition and the asserted cause.”  Malam v. State, Dept. of Corrections, 492 S.W.3d 926, 929 (Mo. 2016) (quoting Gordon v. City of Ellisville, 268 S.W.3d 454, 461 (Mo. App. 2008)).

When a fact at issue is so technical or complex that no fact finder could resolve the issue without expert testimony, expert testimony is necessary and, therefore, required.  For example, expert testimony has been required to explain the results of medical tests and blood work . . . or to establish causation when there is a sophisticated injury that involves a highly scientific technique for diagnosis.

Stone v. Missouri Dept. of Health & Senior Services, 350 S.W.3d 14, 21 (Mo. 2011) (citations and quotation marks omitted).  “Proof of causation generally requires expert testimony to establish the causal connection between the accident and the injury.”  Host v. BNSF Railway Co., 460 S.W.3d 87, 104 (Mo. App. 2015).

This rule is applied in toxic tort and product liability litigation.  “[C]ausation in cases involving exposure to a toxic substance typically requires a certain degree of scientific expertise.”  Brown v. Seven Trails Investors, LLC, 456 S.W.3d 864, 869 (Mo. App. 2014).  “The nature of [a] medication’s side effects, the doses necessary to manifest those effects, and the biomedical interaction of [different] medications are all matters beyond that of a layperson’s common knowledge and experience.”  Love v. Waring, 560 S.W.3d 614, 620 (Mo. App. 2018).  “[E]xpert testimony is necessary” in product liability cases where “the lay jury [does] not possess the experience or knowledge of the subject matter sufficient to enable them to reach an intelligent opinion without help.”  Pro Service Automotive, L.L.C. v. Lenan Corp., 469 F.3d 1210, 1214 (8th Cir. 2006) (applying Missouri law) (quoting Wright v. Barr, 62 S.W.3d 509, 524 (Mo. App. 2001)).  See Redd v. DePuy Orthopaedics, Inc., 700 F. Appx. 551, 555 (8th Cir. 2017) (summary judgment affirmed because “the fracture of [plaintiff’s] . . . implant was a sophisticated injury, and [plaintiff] lacked any admissible expert testimony on the cause of that fracture”) (applying Missouri law); Menz v. New Holland North America, Inc., 507 F.3d 1107, 1112 (8th Cir. 2007) (“The district court did not abuse its discretion in concluding a lay jury would lack the experience and knowledge necessary to determine causation on [plaintiff’s] warnings claim without the aid of expert testimony.”) (applying Missouri law); Turner v. Iowa Fire Equipment Co., 229 F.3d 1202, 1210 (8th Cir. 2000) (“Without [an expert] opinion that the [product] exposure caused the . . . injuries, [plaintiffs] cannot prove causation.”) (applying Missouri law); Howard v. Bosch Thermotechnology Corp., 2018 WL 2087259, at *3 (E.D. Mo. May 4, 2018) (expert testimony “is necessary if determining a relevant factual issue involves information that is so complex or technical that no fact finder could resolve the issue without help”); Hoover v. Bayer Healthcare Pharmaceuticals, Inc., 2017 WL 2313177, at *4 (W.D. Mo. Jan. 11, 2017) (“Without reliable expert testimony concerning specific causation . . ., the Court concludes Plaintiff is unable to establish the necessary element of causation.”); Martin v. Crown Equipment Corp., 2008 WL 11337826, at *3 (W.D. Mo. Jan. 16, 2008) (“[w]hen a failure-to-warn claim involves technical and complex machinery not commonly utilized by typical lay jurors, it is appropriate for the Court to require expert testimony”); Hilton v. Ethicon, Inc., 2007 WL 541603, at *3 (W.D. Mo. Feb. 16, 2007) (“Without such expert testimony, Plaintiff cannot establish causation.”); Looney v. Zimmer, Inc., 2004 WL 1918720, at *5 (W.D. Mo. Aug. 19, 2004) (“When an injury is sophisticated, proof of causation generally must be established by expert testimony.”); Shaffer v. Amada America, Inc., 335 F. Supp.2d 992, 998 (E.D. Mo. 2003) (plaintiff “needs competent expert testimony to establish that this [product] is defective and unreasonably dangerous”); Glastetter v. Novartis Pharmaceuticals Corp., 107 F. Supp.2d 1015, 1045 (E.D. Mo. 2000) (Daubert exclusion of plaintiff’s experts created “the absence of any scientifically valid evidence supporting plaintiffs’ theory of causation,” requiring summary judgment), aff’d, 252 F.3d 986 (8th Cir. 2001);  Eppler v. Ciba-Geigy Corp., 860 F. Supp. 1391, 1395 (W.D. Mo. 1994) (in “a product liability action of a highly technical and scientific nature, expert testimony is essential to establish causation”).

Montana

In Montana, matters “not readily apparent to a layman” “obligate[ the plaintiff] to present expert testimony.”  Dubiel v. Montana Dep’t of Transportation, 272 P.3d 66, 70 (Mont. 2012).  “[E]xpert testimony is required when the issue presented is sufficiently beyond the common experience of the trier of fact and the expert testimony will assist the trier of fact in determining the issue or understanding the evidence.”  Hinkle v. Shepherd School Dist. No. 37, 93 P.3d 1239, 1246 (Mont. 2004).  Accord Dayberry v. City of East Helena, 80 P.3d 1218, 1220-21 (Mont. 2003) (same language).

A Plaintiff’s testimony alone is not sufficient “to establish causation of the injury where the nature of the injury is such that laymen can neither plainly see, nor infer from the injury. . . .  Rather, qualified medical testimony from an expert witness is necessary to prove the cause … of such injuries.”

Green v. Montana Dep’t of Public Health & Human Services, 2014 WL 12591834, at *6 (D. Mont. Jan. 3, 2014) (quoting Bleek v. Supervalu, Inc., 95 F. Supp.2d 1118, 1121 (D. Mont. 2000)).  See Horob v. McCone County, 2010 WL 5441961, at *1 (D. Mont. Dec. 28, 2010) (“evidence of causation must be proved with expert medical testimony unless the cause of injury is obvious”), aff’d, 507 F. Appx. 679 (9th Cir. 2013); Wilderness Development, LLC v. Hash, 606 F. Supp.2d 1275, 1281 (D. Mont. 2009) (“the causation issue will require the trier of fact to resolve issues beyond the common experience and knowledge of lay people and, thus, expert testimony will be required”).

The same is true in product liability and toxic tort cases.  In a prescription drug case the Montana Supreme Court held:

There are no Montana cases specifically holding that a plaintiff must produce expert testimony to sustain an action against a drug company for failure to warn adequately of side effects of its products.  There are, however, numerous Montana decisions to the effect that, in a malpractice suit . . . , expert evidence is the only proper guide and without it a plaintiff cannot recover.  We hold that the reasoning of these decisions extends to the situation involved here.  In matters with respect to which a layman can have no knowledge at all, the court and jury must be dependent on expert evidence.  The adequacy of a warning directed to physicians is such a matter.

Hill v. E.R. Squibb & Sons, 592 P.2d 1383, 1388 (Mont. 1979) (citations omitted).  Where a product liability “case involves matters beyond the common experience of a lay juror . . ., summary judgment dismissal is warranted if the plaintiff fails to present expert testimony necessary to prove the elements of his negligence claim.”  Stacy v. BNSF Railway Co., 2015 WL 1433679, at *2 (D. Mont. March 27, 2015).  See Wilhelm v. Pfizer, Inc., 2016 WL 5030359, at *4 (D. Nev. Sept. 19, 2016) “the Court finds that expert testimony is required to establish causation as to all of [plaintiff’s] claims”) (applying Montana law); Brumbaugh v. Sandoz Pharmaceutical Corp., 77 F. Supp.2d 1153, 1157 (D. Mont. 1999) (without expert testimony, “plaintiff is unable to generate a genuine issue of material fact with respect to causation, an essential element of her claim”).

Nebraska

Nebraska courts hold that “[e]xpert testimony is almost always required to prove proximate causation.”  Ewers v. Saunders County, 906 N.W.2d 653, 664 (Neb. 2018) (quoting Thone v. Regional West Medical Center, 745 N.W.2d 898, 908 (Neb. 2008)).  Medically complicated questions requir[e] expert testimony” so that “the cause and extent of [plaintiff’s] injuries must be substantiated by expert testimony.”  Doe v. Zedek, 587 N.W.2d 885, 891-92 (Neb. 1999).  “Unless its nature and effect are plainly apparent, an injury is a subjective condition requiring an expert opinion to establish a causal relationship between the incident and the injury or disability.”  Bernhardt v. County of Scotts Bluff, 482 N.W.2d 262, 263 (Neb. 1992) (syllabus).

[W]here the claimed injuries are of such a character as to require skilled and professional persons to determine the cause and extent thereof, the question is one of science.  Such a question must necessarily be determined from testimony of skilled professional persons and cannot be determined from the testimony of unskilled witnesses having no scientific knowledge of such injuries.

Hohnstein v. W.C. Frank, 468 N.W.2d 597, 602 (Neb. 1991).

In product liability cases, “[e]xpert evidence is required to establish the elements of causation and defect.”  Barrett v. Rhodia, Inc., 606 F.3d 975, 984 (8th Cir. 2010) (applying Nebraska law).  Like other “cases involving complex technical, medical, or scientific issues, causation must be established by expert testimony.”  Vallejo v. Amgen, Inc., 274 F. Supp.3d 922, 925 (D. Neb. 2017), aff’d, 902 F.3d 733 (8th Cir. 2018).

Ordinarily, in medical cases, product defect and medical causation must be established by expert testimony.  Similarly, the lack of expert testimony on the question of causation results in an insufficiency of proof where the issue involves technical, scientific or medical matters which are beyond the common knowledge or experience of jurors and the jury could only speculate as to what inference to draw.  Where the exact nature and probable genesis of a particular type of injury involves complicated medical questions far removed from the ordinary experience and knowledge of laymen, only an expert can give competent opinion evidence as to the cause of the injury.

Uribe v. Sofamor, S.N.C., 1999 WL 1129703, at *7 (D. Neb. Aug. 16, 1999) (citations, quotation marks, and footnote omitted).  See Schafersman v. Agland Coop, 681 N.W.2d 47, 56 (Neb. 2004) (“the court correctly entered summary judgment” in product liability case after excluding plaintiff’s experts); “whether or not a drug causes an individual to [suffer injury] is a complex factual question”; Grant v. Pharmavite, LLC, 452 F. Supp.2d 903, 910 (D. Neb. 2006) (“Without evidence to establish both general and specific causation, plaintiffs cannot survive defendants’ motions for summary judgment.”); Nuzum v. Chlorella, 2006 WL 3825111, at *2 (D. Neb. Dec. 27, 2006) (“the plaintiff cannot establish essential elements of his products liability claim without expert testimony”).

Similarly, “expert testimony was necessary to establish the basis for an inference that [plaintiff’s] injuries were caused by the inhalation of fumes.”  McNeel v. Union Pacific Railroad Co., 753 N.W.2d 321, 329 (Neb. 2008).  “In a toxic tort case, the plaintiff’s expert evidence must show that the toxin was the cause of the plaintiff’s injury.”  Barrett, 606 F.3d at 984 (citation and quotation marks omitted).

Nevada

Under Nevada law, “generally, because an injury is a subjective condition, an expert opinion is required to establish a causal connection between the incident or injury and disability.”  Grover C. Dils Medical Center v. Menditto, 112 P.3d 1093, 1100 (Nev. 2005).  “[I]f the plaintiff’s medical expert cannot form an opinion . . ., there is nothing on the record with which a jury can make a decision.”  Morsicato v. Sav-On Drug Stores, Inc., 111 P.3d 1112, 1116 (Nev. 2005) (citation and quotation marks omitted).  “Causation in toxic tort litigation is generally proven by expert testimony.”  Jernee v. Kennametal, Inc., 2015 WL 134767, at *1 (Nev. Jan. 8, 2015) (unpublished).  “When, as here, the cause of injuries is not immediately apparent, the opinion as to the cause should be given by one qualified as a medical expert.”  Lord v. State, 806 P.2d 548, 551 (Nev. 1991).

[Plaintiff] failed to timely disclose any expert witness or treating physician to testify regarding causation. . . .  Since [plaintiff] could not show causation, he failed to establish each element of his negligence claims.  Thus, summary judgment was appropriate.

Elliott v. City Center Veer Towers Development, LLC, 2018 WL 2041490, at *2 (Nev. App. April 20, 2018) (also quoting and following Grover).

Thus, “[u]nder Nevada law, Plaintiffs must produce medical expert testimony to establish causation, particularly where the cause of death is not immediately apparent.”  Neal-Lomax v. Las Vegas Metro. Police Dep’t, 574 F. Supp.2d 1193, 1199 (D. Nev. 2008), aff’d, 371 F. Appx. 752 (9th Cir. 2010).  See Elliott v. Prescott Cos., LLC, 2018 WL 3731087, at *5 (D. Nev. Aug. 6, 2018) (“the causal relationship between [the] chemicals and [plaintiff’s] alleged injuries is not immediately apparent or within the comprehension of the ordinary layperson.  As such, expert testimony is required to prove causation.”); Blackmon v. New Albertson’s Inc., 2012 WL 3613956, at *3 (D. Nev. Aug. 21, 2012) (“Nevada law requires an expert opinion to establish a causal connection between the incident and the injury.”); Thompson v. TRW Automotive, Inc., 2015 WL 5474448, at *5 (D. Nev. Sept. 17, 2015) (“expert testimony . . . is necessary because the issues are complicated and often far beyond an ordinary juror’s understanding”) (citation and quotation marks omitted), aff’d, 694 F. Appx. 566 (9th Cir. 2017); Blackmon v. New Albertson’s, Inc., 2011 WL 4958631, at *2 (D. Nev. Oct. 17, 2011) (“It is well-settled law that in a personal injury action causation must be proven within a reasonable medical probability based upon competent medical testimony.”) (citation and quotation marks omitted); Duenas v. United States, 2006 WL 8441980, at *5 (D. Nev. Feb. 15, 2006) (“On the basis that Plaintiff has failed to put forth reliable medical expert testimony or treatises as to injuries, we will grant Defendant’s motion for summary judgment”); Layton v. Yankee Caithness Joint Venture, L.P., 774 F. Supp. 576, 580 (D. Nev. 1991) (“[W]here a question of fact is beyond the comprehension of the ordinary lay person, expert testimony is required to prove that fact.”).

New Hampshire

New Hampshire law holds that “[e]xpert testimony is required where the subject presented is so distinctly related to some science, profession or occupation as to be beyond the ken of the average layperson.”  Estate of Sicotte v. Lubin & Meyer, P.C., 959 A.2d 236, 239 (N.H. 2008).  “The medical causation of [an . . .] injury of this nature is a matter properly within the province of medical experts.”  Appeal of Briggs, 645 A.2d 655, 659 (N.H. 1994).

To determine whether expert testimony is required, we must determine whether this issue . . . is within the realm of common knowledge and everyday experience of the average layman, or whether an expert opinion is needed to preclude the jury from engaging in idle speculation. . . .  Expert testimony is required if any inference of the requisite causal link must depend on observation and analysis outside the common experience of jurors.

Stachulski v. Apple New England, LLC, 191 A.3d 1231, 1241 (N.H. 2018) (citations and quotation marks omitted).  See Smith v. HCA Health Services, Inc., 977 A.2d 534, 539 (N.H. 2009) (“The plaintiffs’ claims are actions for medical injury that require expert testimony”); Carbone v. Tierney, 864 A.2d 308, 315 (N.H. 2004) (“The facts of this case are thus sufficiently complicated to require expert testimony with respect to causation.”); Sawyer v. Purdue Pharmaceutical Corp., 2013 WL 6840145, at *7 (M.D. Pa. Dec. 27, 2013) (“[o]nly a qualified expert could provide the jury an informed basis upon which to conclude that [defendant] did not exercise reasonable care in the manufacture and design of [its drug]”; “the jury could reasonably conclude that [defendant] provided inadequate warnings only with the help of expert opinion”) (applying New Hampshire law); Grimes v. Hoffmann-LaRoche, Inc., 907 F. Supp. 33, 38-39 (D.N.H. 1995) (granting summary judgment in prescription medical product liability action after excluding plaintiff’s expert).

New Jersey

A plaintiff in New Jersey is “required to produce an expert” when the case involves “a complex process involving assessment of a myriad of factors that is beyond the ken of the average juror.”  Davis v. Brickman Landscaping, Ltd., 98 A.3d 1173, 1180 (N.J. 2014).

[C]ertain claims require expert testimony.  In tort actions, whether expert testimony is needed in respect of breach of duty depends on whether the matter to be dealt with is so esoteric that jurors of common judgment and experience cannot form a valid judgment about a party’s conduct.  Similarly, cases have found expert testimony to be required in certain types of actions in connection with proof of other tort elements.

Phillips v. Gelpke, 921 A.2d 1067, 1073 (N.J. 2007) (citations and quotation marks omitted).

Thus, “New Jersey law does require expert testimony, however, in cases where lay jurors confront causation issues that are too complex to be understood without the assistance of specialized expert testimony.”  Tormenia v. First Investors Realty Co., 251 F.3d 128, 132 (3d Cir. 2000) (applying New Jersey law) (emphasis original).  Tormenia followed Kelly v. Borwegen,

[W]here a claimed disability is the natural result of the injuries sustained, the jury may, without expert opinion, find that the injuries caused such disability.  However, when an injury is such as to require skilled men to determine its cause and extent, the question is one of science, and must be established by skilled professional persons.

230 A.2d 532, 534 (N.J. Super. App. Div. 1967) (citation and quotation marks omitted).  Similarly, “[w]here the allegedly defective product involves a complex instrumentality, a plaintiff is required to provide expert testimony,” since “[e]xpert testimony is necessary to assist the fact finder in understanding ‘the mechanical intricacies of the instrumentality.”  Lauder v. Teaneck Volunteer Ambulance Corps, 845 A.2d 1271, 1277 (N.J. Super. App. Div. 2004).  “A factfinder should not be allowed to speculate without the assistance of expert testimony in an area where the average person could not be expected to have sufficient knowledge or experience.”  State v. Doriguzzi, 760 A.2d 336, 341 (New Jersey Super. App. Div. 2000) (citation omitted).  A more recent decision of the same court agrees:

The topic is plainly outside the common knowledge of the average juror.  Plaintiff needed a medical expert to address these key issues of medical causation, but did not retain one.  This critical shortcoming pertains as to both the wrongful death claim and the survival claim. . . .  [A] lay inference is simply not enough to get the complex issues of medical causation before a jury.

Quail v. Shop-Rite Supermarkets, Inc., 188 A.3d 348, 358 (N.J. Super. App. Div. 2018) (citation omitted).

New Jersey’s expert testimony requirement also applies in product liability and toxic tort cases.  “[W]e hold that in toxic-tort litigation, a scientific theory of causation . . . must be proffered by an expert who is sufficiently qualified.”  Rubanick v. Witco Chemical Corp., 593 A.2d 733, 747-48 (N.J. 1991).  “It is well-settled law that where the allegedly defective product involves a complex instrumentality, a plaintiff is required to provide expert testimony.”  Toms v. J.C. Penney Co., 2007 WL 2893052, at *4 (D.N.J. Sept. 28, 2007), aff’d, 304 F. Appx. 121 (3d Cir. 2008).  “When the proofs involve a defect in a complex instrumentality, an expert is frequently required to assist the jury in understanding the mechanical intricacies and weighing competing theories of causation.”  Ford Motor Credit Co., LLC v. Mendola, 448 A.3d 366, 372 (N.J. Super. App. Div. 2012) (citing Lauder).

Courts generally recognize that plaintiffs in products liability cases must offer admissible expert testimony regarding both general causation and specific causation. . . .  Expert testimony is generally required in product liability cases because it prevents the jury from engaging in speculation in determining the causal link between using or ingesting the product and the injuries complained of following that use.  Determining that causal link typically requires complex medical information beyond the knowledge, understanding, and experience of a lay juror.  Expert testimony typically provides this link.

In re Benicar (Olmesartan) Products Liability Litigation, 2016 WL 6652358, at *2 (D.N.J. Nov. 9, 2016) (citations omitted).  See Ace Pallet Corp. v. Consolidated Rail Corp., 764 F. Appx. 197, 199 (3d Cir. 2019) (affirming summary judgment under Tormenia following exclusion of plaintiff’s experts) (applying New Jersey law); Koplove v. Ford Motor Co., 795 F.2d 15, 18 (3d Cir. 1986) (“a rational jury could not find the defendant liable without some expert analysis of the available information which implicated it”); Huddell v. Levin, 537 F.2d 726, 736 (3d Cir. 1976) (“where the issue concerns a product’s design . . . expert opinion is the only available method to establish defectiveness”) (applying New Jersey law); Hettinger v. Speedline Technology, Inc., 2014 WL 5410620, at *5 (D.N.J. Oct. 22, 2014) (“In the instant matter, an expert opinion is required to prove this vital element of causation for both the design defect and failure to warn claims because the [product] constitutes a ‘complex instrumentality.’”); Sampson v. Glock, Inc., 2014 WL 1225581, at *3 (D.N.J. March 24, 2014) (“given the complex nature of the [product], Plaintiff must rely on the testimony of an expert”); Leese v. Martin, 2013 WL 5476415, at *8 (D.N.J. Sept. 30, 2013) (“As a general proposition, expert testimony is required to demonstrate causation in toxic tort cases.”) (citations omitted); Mays v. General Binding Corp., 2013 WL 1986393, at *6 (D.N.J. May 10, 2013) (quoting Lauder), aff’d, 565 F. Appx. 94 (3d Cir. 2014); Sanders v. Rosenberg, 2008 WL 1732980, at *3 (D.N.J. April 10, 2008) (“in cases concerning toxic torts . . ., testimony of an expert is required, in particular with regard to causation”); Amico v. Duracal Cement, 2006 WL 2319313, at *7 (D.N.J. Aug. 9, 2006) (“Without expert medical testimony there is no evidence of causation to support any of [plaintiff’s] negligence/products liability claims.”); Appleby v. Glaxo Wellcome, Inc., 2005 WL 3440440, at *7 (D.N.J. Dec. 13, 2005) (“Without an expert, it is impossible to evaluate the evidence to ascertain whether the risk of [the drug] sufficiently outweighs its benefit”); Ortiz v. Yale Materials Handling Corp., 2005 WL 2044923, at *2 (D.N.J. Aug. 24, 2005) (“Where the allegedly defective product involves a complex instrumentality, a plaintiff is required to provide expert testimony.”); In re Norplant Contraceptive Products Liability Litigation, 215 F. Supp.2d 795, 830 (E.D. Tex. 2002) (“Evidence of general causation must be provided in the form of expert testimony.”) (citations omitted) (applying New Jersey law); Snodgrass v. Ford Motor Co., 2001 WL 37118915, at *5 (D.N.J. Aug. 31, 2001) (“Where a plaintiff fails to come forward with an expert’s report on a complicated causation issue, summary judgment is appropriate.”); Rutigliano v. Valley Business Forms, 929 F. Supp. 779, 783 (D.N.J. 1996) (“Plaintiff’s case requires expert testimony to satisfy her burden with respect to both general causation and specific causation.”), aff’d, 118 F.3d 1577 (3d Cir. 1997).

New Mexico

Expert testimony in New Mexico “is required to establish an element of a claim or defense [because] it would assist the jury to understand issues in the case that are beyond their knowledge.”  State v. Campbell, 157 P.3d 722, 725 (N.M. 2007).  “To prove a proposition to a reasonable medical probability requires expert medical testimony establishing that the proposition is more likely than not.”  Baca v. Bueno Foods, 766 P.2d 1332, 1334 (N.M. 1988) (citation omitted).  With “issues involv[ing] a complex professional assessment.  It follows that jurors would also require expert testimony.”  Holley v. Evangelical Lutheran Good Samaritan Society, 588 F. Appx. 792, 796 (10th Cir. 2014) (applying New Mexico law).  Where “expert knowledge is essential to the formation of an intelligent opinion, only an expert can competently give opinion evidence as to the cause of death, disease, or a physical condition.”  Woods v. Brumlop, 377 P.2d 520, 522 (N.M. 1962).  See Holley v. Evangelical Lutheran Good Samaritan Society, 588 F. Appx. 792, 796 (10th Cir. 2014) (summary judgment affirmed where issues were “not within the common knowledge ordinarily possessed by an average person,” and plaintiff’s expert excluded) (applying New Mexico law); Montoya v. Ramos, 2017 WL 5654791, at *1 (D.N.M. Sept. 25, 2017) (“diagnoses of complex mental conditions are generally beyond the common experience of lay persons and require special skill or knowledge”); Safford v. Wal-Mart Stores, Inc., 2017 WL 2306410, at *6 (D.N.M. Feb. 16, 2017) (“plaintiffs cannot prevail on the issue of medical causation without expert testimony directly supporting their conclusion”) (citation omitted); American Mechanical Solutions, L.L.C. v. Northland Process Piping, Inc., 184 F. Supp.3d 1030, 1067 (D.N.M. 2016) (“when the issue of causation . . . cannot be determined by resort to common knowledge that an average person ordinarily possesses, New Mexico law requires expert testimony”); Duke v. Garcia, 2014 WL 1333151, at *3 (D.N.M. Feb. 28, 2014) (“the medical situation is complex, and actions involving medically complicated injuries require expert testimony on causation”) (citation and quotation marks omitted).

Similar considerations mandate reliance on expert witnesses in product liability and toxic tort cases in New Mexico.  In “toxic tort cases like the one before us, the determination of the external cause of a patient’s disease is a complex process . . . which requires specialized scientific knowledge regarding the external agents involved.”  Parkhill v. Alderman-Cave Milling & Grain Co., 245 P.3d 585, 590 (N.M. App. 2010).  Thus, in Firstenberg v. Monribot, 350 P.3d 1205 (N.M. App. 2015), another toxic tort case, the court, “[h]aving concluded that [plaintiff’s] arguments regarding . . . expert witness rulings provide no basis for reversal, . . . further conclude[d] that the court properly granted summary judgment in favor of Defendants.”  Id. at 1215.  Likewise, Farris v. Intel Corp., 493 F. Supp.2d 1174 (D.N.M. 2007), held:

General causation and specific causation are essential elements of Plaintiff’s prima facie case for each claim asserted in this litigation.  Expert testimony is necessary to make this showing since this is a toxic tort lawsuit.

Id. at 1186 (citation omitted).  Similarly, in R.R. v. Dandade, 2017 WL 2117386 (N.M. App. April 25, 2017), plaintiff had no expert to establish the relevant injury was drug related.  Thus, “[t]he district court properly granted summary judgment” because “a determination of the external cause of a patient’s condition requires specialized, scientific knowledge regarding those external agents involved.”  Id. at *6 (citation omitted).  See Derrick v. Standard Nutrition Co., 2019 WL 2024960, at *7 (D.N.M. May 8, 2019) (“Such medical knowledge is, as a matter of law, outside the realm of common experience.  Because Plaintiffs have not secured expert testimony on causation, they cannot withstand Defendant’s motion for summary judgment.”).

New York

The New York Court of Appeals was one of the first courts to articulate the modern requirement for expert testimony in tort cases in Meiselman v. Crown Heights Hospital:

[E]xpert medical opinion evidence . . . is required, when the subject-matter to be inquired about is presumed not to be within common knowledge and experience and when legal inference predominates over statement of fact . . .; but where the matters are within the experience and observation of the ordinary jurymen from which they may draw their own conclusions and the facts are of such a nature as to require no special knowledge or skill, the opinion of experts is unnecessary.

34 N.E.2d 367, 370 (N.Y. 1941).  See Fiore v. Galang, 478 N.E.2d 188, 189 (N.Y. 1985)  (error under Meiselman not to grant summary judgment because “expert medical opinion evidence is required to demonstrate merit” ).

Thus, in New York, “to establish causation, [Plaintiffs] must offer admissible expert testimony regarding both general causation . . . and specific causation.”  Amorgianos v. National Railroad Passenger Corp., 303 F.3d 256, 268 (2d Cir. 2002) (applying New York law).  It is a “well-established requirement that an expert opinion on causation set forth a plaintiff’s exposure to a toxin, that the toxin is capable of causing the particular illness (general causation) and that plaintiff was exposed to sufficient levels of the toxin to cause the illness (specific causation).”  In re New York City Asbestos Litigation, 11 N.Y.S.3d 416, 426 (N.Y. Sup. 2015).  See Fitzpatrick v. Currie, 861 N.Y.S.2d 431, 434 (N.Y. App. Div. 2008) (“While the opinion of an expert may not always be necessary in establishing a products liability case, the complex issues involved in the design and operation of [this product] make expert proof imperative.”); Marazzo v. Gilbert, 542 N.Y.S.2d 793, 794 (N.Y. App. Div. 1989) (“It was incumbent upon the plaintiff to elicit expert medical testimony . . . and, in the absence of such testimony on the issue of causation, the claim was properly dismissed”); Glowczenski v. Taser International, Inc., 594 F. Appx. 723, 725 (2d Cir. 2014) (“absent an expert . . . [plaintiffs] cannot prevail on either their products liability or wrongful death claims” because plaintiffs’ “tort claims against [defendant] fail for want of evidence on causation”) (applying New York law); Alaimo v. 3M Co., 306 F. Appx. 704 (2d Cir. 2009) (plaintiffs “were required to prove a causal link between use of the [product] at issue and the injury . . . by use of expert testimony”) (applying New York law); Brooks v. Outboard Marine Corp., 234 F.3d 89, 92 (2d Cir. 2000) (“summary judgment was properly granted” where plaintiff’s expert was excluded; plaintiff “has no evidence in the record to support his [design defect] theory”) (applying New York law); Williams v. Coca Cola Co., 2018 WL 3069208, at *5 (N.D.N.Y. June 21, 2018) (“[g]iven plaintiff’s failure to offer any expert proof on the issue of general and/or specific causation, defendant’s motion for summary judgment is granted”); Young v. Southwest Airlines Co., 2017 WL 1247921, at *3 (E.D.N.Y. Feb. 3, 2017) (“the medical effect on the human system of the infliction of injuries is not generally within the sphere of the common knowledge of the lay person”); Jaquez v. Flores, 2016 WL 1267780, at *4 (S.D.N.Y. March 30, 2016) (“Plaintiffs are thus required to produce admissible expert medical evidence on causation in order to sustain their wrongful death claim. They have chosen not to do so.”); Mallozzi v. EcoSMART Technologies, Inc., 2013 WL 2415677, at *14 (E.D.N.Y. May 31, 2013) (“Without . . . expert testimony, plaintiff cannot establish that the product was the proximate cause of plaintiff’s injuries.”); Kennedy v. New York Presbyterian Hospital, 2011 WL 2847839, at *4 (S.D.N.Y. July 6, 2011) (summary judgment granted; “Plaintiff must − but did not − submit expert medical opinion supporting her theory of causation”).  Also, “Under New York law, a plaintiff seeking to establish a design defect is generally required to provide expert testimony as to the feasibility and efficacy of alternative designs.”  Cuntan v. Hitachi KOKI USA, Ltd., 2009 WL 3334364, at *6 (E.D.N.Y. Oct. 15, 2009) (collecting cases).  See Guarascio v. Drake Associates, Inc., 582 F. Supp.2d 459, 463 (S.D.N.Y. 2008) (same).

In prescription medical product cases, where the plaintiff “suffered a complex injury,” expert testimony was essential.

Implantation of the . . . device involved complicated surgery.  Additionally, the . . . device implanted in [plaintiff] was not one with which an ordinary person would come in contact.  The issue of causation in such a complicated medical case, therefore, was one beyond the sphere of the ordinary juryman and required expert testimony.

Fane v. Zimmer, Inc., 927 F.2d 124, 131 (2d Cir. 1991) (applying New York law).  See Sura v. Zimmer, Inc., 768 F. Appx. 58, 59 (2d Cir. 2019) (in medical device case, “determining the cause of these symptoms is beyond the experience and observation of the ordinary jury, [plaintiff] needed expert testimony”); N.K. v. Abbott Laboratories, 731 F. Appx. 24, 27 (2d Cir. 2018) (“New York law requires expert witnesses to establish specific causation.”) (citing Meiselman); Tomaselli v. New York & Presbyterian Hospital, 728 F. Appx. 41, 43 (2d Cir. 2018) (following Fane in medical device case) (applying New York law); Donovan v. Centerpulse Spine Tech, Inc., 416 F. Appx. 104, 106 (2d Cir. 2011) (“ordinarily, expert medical opinion evidence is required, when the subject-matter to be inquired about is presumed not to be within common knowledge and experience”) (citation and quotation marks omitted) (applying New York law); Riegel v. Medtronic, Inc., 451 F.3d 104, 127 (2d Cir. 2006) (“because there was no competent evidence excluding [the defendant’s] proffered causes” of the plaintiffs’ injury after their expert was excluded, “there were no genuine issues of material fact for a jury on this claim”), aff’d, 552 U.S. 312 (2008); Washburn v. Merck & Co., 213 F.3d 627 (2d Cir. 2000) (affirming both expert exclusion and summary judgment) (applying New York law); Gidora v. Howmedica Osteonics Corp., 2019 WL 1129127, at *3 (S.D.N.Y. March 12, 2019) (“Where a claim raises complex issues requiring expert testimony to establish a fundamental element of the claim, summary judgment is appropriate if a plaintiff fails to produce a qualified expert or the plaintiff has been precluded from calling his or her proffered expert.”); Byrd v. Janssen Pharmaceuticals, Inc., 333 F. Supp.3d 111, 127-31 (N.D.N.Y. 2018) (judgment as a matter of law appropriate where plaintiff’s expert testimony failed to establish general causation); Adeghe v. Janssen Pharmaceuticals, Inc., 2018 WL 4112815, at *3 (S.D.N.Y. Aug. 29, 2018) (“because of the complex chemistry and biology involved in assessing the design of [the drug] and its alternatives, expert testimony is necessary”); Coleson v. Janssen Pharmaceutical, Inc., 251 F. Supp.3d 716, 723 (S.D.N.Y. 2017) (“Without competent medical expert testimony on the issue of causation, a jury would be left only to theorize as to how Plaintiff came to suffer from” his claimed injuries); Vargas v. Ortho-McNeil Pharmaceutical, Inc., 2013 WL 3776628, at *4 (N.D. Ohio July 17, 2013) (“It is clear that the determination of causation in this case requires the testimony of medical experts, which Plaintiff has repeatedly failed to provide.”) (applying New York law); In re Trasylol Products Liability Litigation, 2013 WL 1343529, at *13 (S.D. Fla. April 2, 2013) (after experts are excluded, all plaintiff’s claims “must fail”) (applying New York law); Dolphin v. Synthes (USA) Ltd., 2012 WL 13059723, at *3 (S.D.N.Y. Feb. 16, 2012) (“in cases that concern more complicated medical procedures, a jury cannot reasonably be expected to infer issues of causation and a medical expert is required”) (citing Fane); Maxwell v. Howmedica Osteonics Corp., 713 F. Supp.2d 84, 91 (N.D.N.Y. 2010) (“under New York law, a plaintiff seeking to establish a design defect is required to provide expert testimony as to the feasibility and efficacy of alternative designs”); Nealy v. U.S. Surgical Corp., 587 F. Supp.2d 579, 586 (S.D.N.Y. 2008) (“Expert medical opinion evidence is usually required to show the cause of an injury or disease because the medical effect on the human system of the infliction of injuries is generally not within the sphere of the common knowledge of the lay person.”); Rodriguez v. Mallinckrodt, Inc., 2007 WL 2811061, at *3 (E.D. Mo. Sept. 24, 2007) (“expert medical opinion evidence is required when the subject matter at issue is presumed to be beyond the common knowledge and experience of a jury”) (applying New York law), aff’d, 316 F. Appx. 527 (8th Cir. 2009); Prohaska v. Sofamor, S.N.C., 138 F. Supp.2d 422, 445 (W.D.N.Y. 2001) (“Absent competent medical expert testimony on the issue of causation, plaintiffs cannot prove the elements of a cause of action based in strict products liability or negligence.”); McLellan v. Sofamor-Danek Group, Inc., 1999 WL 222591, at *4 (W.D.N.Y. April 12, 1999) (“When competent medical opinion evidence is required, a judgment as a matter of law is appropriate if the plaintiff fails to adduce such.”) (citing Fane); Saari v. Merck & Co., 961 F. Supp. 387, 392 (N.D.N.Y. 1997) (“in a case such as this where there are complex medical issues, in order for plaintiff to prove that her alleged injuries were caused by defendants’ products, she must introduce expert medical testimony establishing causation”); Krasnopolsky v. Warner-Lambert Co., 799 F. Supp. 1342, 1348 (E.D.N.Y. 1992) (plaintiffs “have failed to submit any type of expert proof, in an affidavit or otherwise, which would establish any causation between [the] injury and the alleged negligence”); McGovern v. Davol, Inc., 2018 WL 1384549, at *7 (N.Y. Sup. March 15, 2018) (“Plaintiff fails to provide a medical expert who could opine that such a [product] defect was a substantial factor in causing Plaintiff’s injury”); Gentile v. Biogen Idec, Inc., 2016 WL 4168942, at *7 (Mass. Super. July 28, 2016) (“Because the adequacy of the warnings cannot be evaluated by a layperson, expert testimony is necessary to resolve the issue.”) (citation omitted) (applying New York law).

North Carolina

In North Carolina “cases involving complicated medical questions far removed from the ordinary experience and knowledge of laymen, only an expert can give competent opinion evidence as to the cause of the injury.”  Holley v. ACTS, Inc., 581 S.E.2d 750, 753 (N.C. 2003).  See Click v. Pilot Freight Carriers, Inc., 265 S.E.2d 389, 391 (N.C. 1980) (same as to the “exact nature and probable genesis of a particular type of injury”).

Due to the complexities of medical science, particularly with respect to diagnosis, methodology and determinations of causation, this Court has held that where the exact nature and probable genesis of a particular type of injury involves complicated medical questions far removed from the ordinary experience and knowledge of laymen, only an expert can give competent opinion evidence as to the cause of the injury.

Young v. Hickory Business Furniture, 538 S.E.2d 912, 915 (N.C. 2000) (citations and quotation marks omitted).  See Campbell v. Duke University Health Systems, Inc., 691 S.E.2d 31, 36 (N.C. App. 2010) (same standards applicable to civil suits); Freeman v. Blue Ridge Paper Products, Inc., 529 F. Appx. 719, 725 (6th Cir. 2013) (“the subject matter of causation in this case is far removed from the ordinary person’s experience, and the matter more closely parallels those cases in which North Carolina courts require expert proof of causation”) (citation omitted) (applying North Carolina law); Free v. Baker, 469 F. Appx. 786, 791 (11th Cir. 2012) (“Expert testimony is required to establish medical causation under North Carolina law.”) (applying North Carolina law); Riggins v. SSC Yanceyville Operating Co., LLC, 2018 WL 4374929, at *3 (M.D.N.C. Sept. 13, 2018)  (“In North Carolina, not only does a plaintiff establish the standard of care with expert testimony, but medical experts are relied upon to show medical causation”) (citation and quotation marks omitted); Phillip v. GEO Group, Inc., 2012 WL 5392120, at *7 (E.D.N.C. Nov. 5, 2012) (“North Carolina courts have applied the requirement for expert medical testimony to actions in which a party claims to have been injured by an airborne toxin”), aff’d, 520 F. Appx. 215 (4th Cir. 2013) (on basis of district court opinion); Butler v. United States, 2011 WL 5191701, at *5 (Mag. M.D.N.C. Aug. 2, 2011) (“where the injury is complicated or unusual, a plaintiff must present expert witness testimony”), adopted, 2011 WL 5170015 (M.D.N.C. Oct. 31, 2011), aff’d, 702 F.3d 749 (4th Cir. 2012); Fontenot v. TASER International, Inc., 2011 WL 2535016, at *8 (W.D.N.C. June 27, 2011) (“In a complex product liability case such as this, a plaintiff must present expert medical testimony to establish causation.”).

Thus, “[i]n North Carolina, a jury award [in a products liability case] cannot be sustained in the absence of expert medical testimony on the issue of causation.”  Hensley v. Danek Medical, Inc., 32 F. Supp.2d 345, 350 (W.D.N.C. 1998).  “Without admissible expert testimony on the issue of specific causation, [plaintiff] cannot prove his claims under North Carolina law.”  In re Testosterone Replacement Therapy Products Liability Litigation Coordinated Pretrial Proceedings, 2017 WL 1833173, at *22 (N.D. Ill. May 8, 2017), reconsideration denied, 2017 WL 2953703 (N.D. Ill. July 11, 2017) (applying North Carolina law).  See Blackmon v. G.UB.MK Constructors, 2016 WL 8674646, at *3 (E.D.N.C. Nov. 11, 2016) (“Without competent expert testimony, evidence of causation remains mere speculation or conjecture and summary judgment in favor of the defendant is appropriate.”) (citation and quotation marks omitted); Ward v. Ortho-McNeil Pharmaceutical, 2015 WL 4110990, at *4 (E.D.N.C. July 7, 2015) (“in cases involving complicated medical questions . . ., only an expert can give competent opinion evidence as to the cause of the injury”) (citation and quotation marks omitted); Lipscomb v. Orkin, Inc., 2014 WL 3510117, at *2 (E.D.N.C. July 14, 2014) (“where a layman can have no well-founded knowledge and can do no more than indulge in mere speculation (as to the cause of a physical condition), there is no proper foundation for a finding by the trier without expert medical testimony”) (citation and quotation marks omitted); Doe v. Ortho-Clinical Diagnostics, Inc., 440 F. Supp.2d 465, 478 (M.D.N.C. 2006) (“Given the Court’s ruling above excluding . . . Plaintiffs’ sole expert on both general and specific causation, Plaintiffs cannot meet their burden of proof on the essential element of causation.”); Dunn v. Sandoz Pharmaceuticals Corp., 275 F. Supp.2d 672, 684 (M.D.N.C. 2003) (entering summary judgment after exclusion of expert left plaintiff unable to prove causation); Ward v. American Medical Systems, Inc., 170 F. Supp.2d 594, 599 (W.D.N.C. 2001) (“a plaintiff is obligated to come forward with expert medical opinion that his medical problems were caused by the defective product”), aff’d, 38 F. Appx. 909 (4th Cir. 2002); Baraukas v. Danek Medical, Inc., 2000 WL 223508, at *3 (M.D.N.C. Jan. 13, 2000) (“Given plaintiffs’ failure to present expert medical testimony on causation . . ., this Court finds that summary judgment for defendants is appropriate.”); Driggers v. Sofamor, S.N.C., 44 F. Supp.2d 760, 764-65 (M.D.N.C. 1998) (“where the injury is complicated, . . . expert medical testimony on the issue of causation must be provided to support a jury award”).

North Dakota

North Dakota cases hold that “expert testimony is required if the issue is beyond the area of common knowledge or lay comprehension, or the issue is not within the ordinary experience of the jurors.”  Klimple v. Bahl, 727 N.W.2d 256, 259 (N.D. 2007) (quoting Leno v. Ehli, 339 N.W.2d 92, 99 (N.D. 1983)).  “[W]hen the causal relationship between a condition affecting the human body and a [defendant’s conduct] is not a matter within the common knowledge or comprehension of a layperson, the party bearing the burden of proof must present expert medical testimony establishing that relationship.”  Halvorson v. Sentry Insurance, 757 N.W.2d 398, 400 (N.D. 2008).  “[A] technical procedure requir[es] an expert witness to establish . . . a causal relationship between the violation and the harm complained of.”  Cartwright v. Tong, 896 N.W.2d 638, 643 (N.D. 2017).

Thus, “[i]n a toxic tort case, a reasonable estimate of exposure by a reliable expert is often the only way a plaintiff can prove specific causation.”  Otto v. Newfield Exploration Co., 2016 WL 7439585, at *3 (D. Mont. Dec. 22, 2016) (applying North Dakota law).

Ohio

“Expert testimony is needed” in Ohio “on complex issues outside the area of common knowledge, such as an injury’s cause and effect.”  Lederer v. St. Rita’s Medical Center, 702 N.E.2d. 476, 483 (Ohio 1997).

“Except as to questions of cause and effect which are so apparent as to be matters of common knowledge, the issue of causal connection between an injury and a specific subsequent physical disability involves a scientific inquiry and must be established by the opinion of medical witnesses competent to express such opinion. . . .  Establishing general causation and specific causation in cases involving exposure to . . . toxic substances involves a scientific inquiry, and thus causation must be established by the testimony of a medical expert.

Terry v. Caputo, 875 N.E.2d 72, 77 (Ohio 2007) (citation and quotation marks omitted) (emphasis original).  See Richards v. Copes-Vulcan, Inc., ___ A.3d ___, 2019 WL 3282056, at *5 (Del. July 22, 2019) (“Under Ohio law, . . . expert medical evidence is required to support specific causation.”) (applying Ohio law).  “The development of a medical condition is typically not within the knowledge of a layperson, thus requiring a medical expert to establish causation of the medical condition.”  Lloyd v. Rogerson, 2019 WL 2721413, at *7 (Ohio App. June 28, 2019) (citation omitted).

In a toxic-tort case, as here, the plaintiff must establish both general and specific causation. . . .  Both causation inquiries involve scientific assessments that must be established through the testimony of a medical expert.  Without this testimony, a plaintiff’s toxic tort claim will fail.

Pluck v. BP Oil Pipeline Co., 640 F.3d 671, 676-77 (6th Cir. 2011) (applying Ohio law).  See Viars v. Ironton, 2016 WL 3670171, at *9 (Ohio App. July 6, 2016) (‘Expert testimony is required to establish general causation and specific causation in cases [where] . . . the determination involves a scientific inquiry into matters beyond the knowledge or experience possessed by lay persons”); Davie v. Nationwide Mutual Insurance Co., 2015 WL 179287, at *4 (Ohio App. Jan. 15, 2015) (“With [plaintiff] failing to offer expert testimony at trial on whether his soft tissue injuries were proximately caused by the tortfeasor’s negligence, the court had no choice but to direct a verdict.”); Bogner v. Titleist Club, L.L.C., 2006 WL 3825228, at *2 (Ohio App. Dec. 29, 2006) (“Expert testimony is needed on complex issues outside the area of the laypersons common knowledge, such as an injury’s cause and effect.”) (citations omitted); Alden v. Phifer Wire Products, Inc., 2005 WL 1407776, at *3 (Ohio App. June 16, 2005) (affirming summary judgment; following Valentine); Valentine v. PPG Industries, Inc., 821 N.E.2d 580, 588 (Ohio App. 2004) (affirming summary judgment because “[t]o prove the proximate cause of a medical condition . . . expert medical testimony ordinarily is necessary”), aff’d, 850 N.E.2d 683 (Ohio 2006); Prysock v. Bahner, 2004 WL 1445565, at *2 (Ohio App. June 29, 2004) (“[e]xpert medical testimony is necessary to show an injury’s cause and effect”); Thompson I.G., LLC v. Edgetech I.G. Inc., 590 F. Appx. 532, 538 (6th Cir. 2014) (“the causation issues here are too complex for the jury to decide without the help of expert testimony”) (applying Ohio law); Madej v. Maiden, 2018 WL 5045768, at *4 (S.D. Ohio Oct. 17, 2018) (“Without expert medical testimony on both general causation and specific causation, a plaintiff’s toxic tort claim will fail”) (quoting Baker); Baker v. Chevron USA, Inc., 680 F. Supp.2d 865, 874 (S.D. Ohio 2010) (following Terry), aff’d, 533 F. Appx. 509 (6th Cir. 2013); Davison v. Cole Sewell Corp., 2006 WL 2129803, at *5 (S.D. Ohio July 28, 2006) (granting summary judgment where plaintiff failed “to establish causation through expert opinion.”), aff’d, 231 F. Appx. 444 (6th Cir. 2007); Day v. NLO, 851 F. Supp. 869, 881 (S.D. Ohio 1994) (medical monitoring claim requires plaintiffs “to show by expert medical testimony that they have increased risk of disease”).

The same considerations control in product liability.  “Ohio law requires expert testimony where aspects of the defect or the proposed alternative designs are technically complex and outside the understanding of a lay juror.”  Newell Rubbermaid, Inc. v. Raymond Corp., 676 F.3d 521, 529 (6th Cir. 2012) (applying Ohio law).  Likewise, in Ohio, “[w]hen a plaintiff alleges that the warning given to a prescribing physician is inadequate, the plaintiff must prove his claim through expert medical testimony.”  Graham v. American Cyanamid Co., 350 F.3d 496, 514 (6th Cir. 2003) (applying Ohio law).  Further, “[u]nder Ohio law, a plaintiff must present expert medical testimony to establish causation when she asserts a specific physical injury, the cause for which is not within common knowledge.”  Botnick v. Zimmer, Inc., 484 F. Supp.2d 715, 724 (N.D. Ohio 2007).

[W]hether a prescription drug is defective and whether it is the proximate cause of an injury are questions which lie outside the knowledge of lay witnesses.  Accordingly, [plaintiff] would have to introduce expert testimony to establish these elements of her claim.

Kerpelis v. Pfizer, Inc., 2004 WL 1326771, at *5 (Ohio App. June 7, 2004).  See Jones v. Roche Laboratories, 616 N.E.2d 545, 548 (Ohio App. 1992) (“expert opinion evidence is necessary for that [inadequate warning] showing”); Taylor v. Medtronics, Inc., 861 F.2d 980, 987-88 (6th Cir. 1988) (affirming summary judgment entered after plaintiff’s expert stricken) (applying Ohio law); Parillo v. Lowe’s Home Centers, LLC, 2017 WL 4124585, at *1 (S.D. Ohio Sept. 18, 2017) (“lay witness opinions regarding the cause of complex medical conditions are . . . irrelevant in a product liability lawsuit”); Z.H. v. Abbott Laboratories, Inc., 2016 WL 5661582, at *4 (N.D. Ohio Sept. 30, 2016) (“Defendants would still be entitled to summary judgment on Plaintiffs’ defective design claim because Plaintiffs offered no expert testimony that [the drug’s] formulation’s risks outweigh its benefits.”); Schmiedebusch v. Mallinckrodt, Inc., 2011 WL 5362066, at *4 (Mag. N.D. Ohio Sept. 13, 2011) (“Under Ohio law, expert medical testimony is required to establish causation of a specific physical injury, if such cause is not within common knowledge.”), adopted, 2011 WL 5362061 (N.D. Ohio Oct. 31, 2011); Utz v. Howmedica Osteonics Corp., 2009 WL 5409046, at *10 (N.D. Ohio March 31, 2009) (“Plaintiffs have failed to proffer expert testimony or other evidence to support this design defect theory.  Accordingly, summary judgment is granted in Defendants’ favor on this claim.”); Saraney v. TAP Pharmaceutical Products, Inc., 2007 WL 148845, at *6 n.3 (N.D. Ohio Jan. 16, 2007) (“The lack of an expert witness proves fatal to [plaintiffs’] product defect claims”); Yanovich v. Sulzer Orthopedics, Inc., 2006 WL 3716812, at *6 (N.D. Ohio Dec. 14, 2006) (summary judgment “warranted on all of plaintiffs’ claims” where plaintiffs had no “expert medical evidence showing that [plaintiff] was injured as a proximate result of the defect” in medical device); Grant v. Memry Corp., 2006 WL 2794732, at *6 (N.D. Ohio Sept. 27, 2006) (“the workings of a [medical device] and the causal relationship between a malfunctioning [medical device] and [plaintiff’s] physical injury are beyond the knowledge and understanding of laypersons, and therefore expert evidence is necessary”); Harmon v. American Red Cross, 2003 WL 22999468, at *1 (N.D. Ohio Dec. 17, 2003)  (“neither [plaintiff’s medical condition] nor what causes that condition is a matter of common knowledge. That being so, plaintiff must provide expert testimony in order to prevail. She not having done so, defendant is entitled to summary judgment.”).

Oklahoma

Under Oklahoma law, “[w]hen an injury is of a nature requiring a skilled and professional person to determine cause and the extent thereof, the scientific question presented must necessarily be determined by testimony of skilled and professional persons.”  Christian v. Gray, 65 P.3d 591, 601-02 (Okla. 2003) (quoting Williams v. Safeway Stores, Inc., 515 P.2d 223, 227 (Okla. 1973)).  The cause of an illness “is a matter of medical science to be established by expert testimony.”  Ruland v. Zenith Construction, 283 P.2d 540, 541 (Okla. 1955)).

In product liability and toxic tort cases as well, “Oklahoma law generally requires expert testimony for complex issues of medical causation.”  Hall v. Conoco, Inc., 886 F.3d 1308, 1317 (10th Cir. 2018) (applying Oklahoma law).

Where, as here, the effect of a defect in a [product] on the human body involved complex medical and biomechanical questions that are beyond a jury’s ordinary knowledge and common experience, expert witness testimony was the best evidence of general causation.  Without such evidence, a jury would have to speculate whether a design defect in the [product] caused or exacerbated [plaintiff’s] injuries.  Such speculation would be error.

Nash v. General Motors Corp., 153 P.3d 73, 75 (Okla. Civ. App. 2007).  See Rodgers v. Beechcraft Corp., 759 F. Appx. 646, 679 (10th Cir. 2018) (“In the context of a complicated [product], Plaintiffs needed expert testimony to prove causation.”) (applying Oklahoma law); Ortiz v. Cooper Tire & Rubber Co., 2015 WL 1498713, at *3 (W.D. Okla. March 31, 2015) (summary judgment granted against warning claim for lack of expert testimony); Carver v. Kia Motors Corp., 2012 WL 119587, at *6 (N.D. Okla. Jan. 12, 2012). (“Without expert testimony . . ., the question of whether [plaintiff’s] injuries were caused by the alleged defect . . . is far too speculative to present to a jury.”).

The same is of course true in prescription medical product liability litigation.  “[U]nder Oklahoma law, a plaintiff must introduce expert testimony if the fact in issue is not within the realm of ordinary experience of mankind.”  Hollander v. Sandoz Pharmaceutical Corp., 289 F.3d 1193, 1214 (10th Cir. 2002) (citation and quotation marks omitted) (applying Oklahoma law).

[P]laintiff is claiming that a complex medical device was defective and she has not identified an expert who will testify in support of her claims.  Expert testimony is essential in cases “[w]here injuries are of a character requiring skilled and professional men to determine the cause and extent thereof.”  Plaintiff alleges that the Device . . . caused her to suffer pain and long term injury, and this is the type of claim that must be supported by expert testimony.

Stewart v. Sulzer Orthopedics, Inc., 2011 WL 2491593, at *4 (N.D. Okla. June 22, 2011) (quoting Alexander v. Smith & Nephew, P.L.C., 98 F. Supp.2d 1276, 1284 (N.D. Okla. 2000)).  See Manous v. Mylan Pharmaceuticals, Inc., 982 F. Supp.2d 1282, 1285 (W.D. Okla. 2013) (summary judgment granted; “there is simply no such expert testimony” about defect or causation); Shrum v. Novartis Pharmaceuticals Corp., 2013 WL 3326645, at *2 (W.D. Okla. June 28, 2013) (“to meet [plaintiff’s] burden of proof on case-specific causation, she must proffer expert testimony on the issue”); Delano v. Smith & Nephew, Inc., 2000 WL 689692, at *1 (Okla. Dist. May 12, 2000) (“A plaintiff must bridge the gap from the [device’s] mechanical behavior to plaintiff’s symptoms with reliable and relevant expert medical causation testimony.”) (citation and quotation marks omitted).

Oregon

In Oregon, “[i]f the issue turns upon some fact beyond the ken of laymen, expert testimony must be produced.”  State v. Davis, 261 P.3d 1197, 1209 n.11 (Or. 2011) (citation and quotation marks omitted).  The “settled rule” is that “where injuries complained of are of such character as to require skilled and professional persons to determine the cause and extent thereof, the question is one of science and must necessarily be determined by testimony of skilled, professional persons.”  Cleland v. Wilcox, 543 P.2d 1032, 1034 (Or. 1975) (quoting Uris v. Compensation Department, 427 P.2d 753, 755 (Or. 1967)).

When the element of causation involves a complex medical question, as a matter of law, no rational juror can find that a plaintiff has established causation unless the plaintiff has presented expert testimony that there is a reasonable medical probability that the alleged negligence caused the plaintiff’s injuries.  The rule prevents jurors from speculating about causation in cases where that determination requires expertise beyond the knowledge and experience of an ordinary lay person.

Pinkerton v. Tri-County Metropolitan Service Dist., 125 P.3d 840, 843 (Or. App. 2005) (citations and quotation marks omitted).  “[W]hether plaintiff was required to present expert testimony “ is “a question of law.”  Vandermay v. Clayton, 984 P.2d 272, 277 (Or. 1999).

“This rule is frequently invoked in negligence cases involving medical causation.”  PacifiCorp v. Northwest Pipeline GP, 879 F. Supp.2d 1171, 1200 (D. Or. 2012).  See Thorson v. Bend Memorial Clinic, 419 P.3d 756, 759 (Or. App. 2018) (plaintiff lacked “the necessary expert testimony in order to avoid summary judgment”); Joshi v. Providence Health Systems Corp., 108 P.3d 1195, 1196 (Or. App. 2005), (“when causation involves a complex medical question, evidence is insufficient to go to the jury without expert testimony”), aff’d, 149 P.3d 1164 (Or. 2006); Chouinard v. Health Ventures, 39 P.3d 951, 954 (Or. App. 2002)  (in case involving “tumors and their effects on the body . . . the issue of causation was a complex medical question that required expert testimony”); Cook v. United Airlines, Inc., 379 F. Appx. 554, 555 (9th Cir. 2010) (“[u]nder Oregon law, [plaintiff] was required to present some expert evidence” of causation) (applying Oregon law).

Similarly, product liability and toxic tort cases require expert testimony on various issues to establish a plaintiff’s prima facie case.  “Under Oregon law, when the element of causation involves a complex medical question, a plaintiff must present expert testimony that there is a reasonable medical probability of causation.”  Phelps v. Wyeth, Inc., 938 F. Supp.2d 1055, 1068 (D. Or. 2013) (citation omitted).

[P]laintiffs must present evidence of both general and specific causation to prevail on their claims. . . .  Thus, plaintiffs must present expert testimony to show by a preponderance of the evidence that [use of the device] can and did cause plaintiffs’ [injury].

McClellan v. I-Flow Corp., 710 F. Supp.2d 1092, 1098 (D. Or. 2010).  See McDowell v. Allied Building Products Corp., 230 P.3d 552, 557 (Or. App. 2010) (affirming dismissal of asbestos case when plaintiff did not produce “prima facie expert proof of causation”); Teater v. Pfizer, Inc., 2013 WL 2455995, at *5 (D. Or. June 6, 2013) (“When, as here, “the element of causation involves a complex medical question, as a matter of law, no rational juror can find that a plaintiff has established causation unless the plaintiff has presented expert testimony. . . that the actions complained of caused the plaintiff’s injuries.”) (citation and quotation marks omitted) (emphasis original); Lusch v. Matrixx Initiatives, Inc., 2007 WL 2816203, at *7 (D. Or. Sept. 25, 2007) (“without expert testimony, plaintiff is similarly unable to create a genuine issue of material fact as to causation”); Rietcheck v. City of Arlington, 2006 WL 1371650, at *3 (D. Or. May 15, 2006) (“[t]he issue of causation concerning exposure to hazardous substances . . . involves a complex medical question” requiring expert testimony).

Pennsylvania

Pennsylvania precedent is explicit that “[e]xpert testimony in support of the plaintiff’s claim is an indispensable requirement in establishing a plaintiff’s right of action” whenever “the treatment and injury typically involved are such that the common knowledge or experience of a layperson is insufficient to form the basis for passing judgment.”  Mitchell v. Shikora, 209 A.3d 307, 315 (Pa. 2019).  “[C]ausation is also a matter generally requiring expert testimony.”  Toogood v. Rogal, 824 A.2d 1140, 1145 (Pa. 2003).  Where “the complexities of the human body place questions as to the cause of pain or injury beyond the knowledge of the average layperson,” Pennsylvania requires expert testimony “that the injury in question did, with a reasonable degree of medical certainty, stem from” the act alleged.  Hamil v. Bashline, 392 A.2d 1280, 1285 (Pa. 1978).

Where, however, the ultimate determinations lie beyond the knowledge or expertise of the average layperson, expert testimony is permitted (and sometimes required) to aid the jury in its understanding of the factors involved and the teaching of the pertinent discipline with respect thereto. . . .   For a plaintiff to make out his cause of action in such a case, therefore, the law requires that expert medical testimony be employed.

Id. (citations omitted).  Accord, e.g., Smith v. German, 253 A.2d 107, 109 (Pa. 1969) (“plaintiff was required to offer expert testimony in order to establish the medical connection” to the accident); Dornon v. Johnston, 218 A.2d 808, 809 (Pa. 1966) (“expert guidance is necessary” whenever an issue is “sufficiently obscure that laymen are unable to make a reasonable determination as to its existence”); Grossman v. Barke, 868 A.2d 561, 567 (Pa. Super. 2005) (“causation is also a matter generally requiring expert testimony” because “a jury of laypersons generally lacks the knowledge to determine the factual issues”) (citation and quotation marks omitted); McMunn v. Babcock & Wilcox Power Generation Group., Inc., 869 F.3d 246, 267 (3d Cir. 2017) (“Expert evidence is generally required when an issue is beyond the ken of a lay jury.”) (applying Pennsylvania law); Cabrera v. Ross Stores, LP, 646 F. Appx. 209, 211 (3d Cir. 2016) (“expert testimony was necessary to establish the causation element of [plaintiff’s] suit”) (applying Pennsylvania law); Furlan v. Schindler Elevator Corp., 516 F. Appx. 201, 207 (3d Cir. 2013) (“[plaintiffs] were unable to meet their burden to establish a claim of negligent maintenance . . . with the exclusion of [their] expert testimony”) (applying Pennsylvania law); Gates v. Rohm & Haas Co., 655 F.3d 255, 265 (3d Cir. 2011) (“[e]xpert testimony is required to prove” the elements of medical monitoring) (quoting Sheridan v. NGK Metals Corp., 609 F.3d 239, 251 (3d Cir. 2010)) (applying Pennsylvania law); Estate of Aptekman v. City of Philadelphia, 127 F. Appx. 619, 622 (3d Cir. 2005) (“Where the causal nexus is not patently obvious, and there is no expert opinion, a factfinder could not simply infer a causal connection.”) (applying Pennsylvania law); In re TMI Litigation, 193 F.3d 613, 723 (3d Cir. 1999) (affirming summary judgment after affirming exclusion of plaintiffs’ experts) (applying Pennsylvania law); Redland Soccer Club, Inc. v. Dept. of Army, 55 F.3d 827, 852 (3d Cir. 1995) (quoting and following Hamil) (applying Pennsylvania law); N’Jai v. Bentz, 2016 WL 7404550, at *3 (W.D. Pa. Dec. 22, 2016) (“Pennsylvania and Federal courts have consistently rejected a plaintiff’s attempt to establish causation in a toxic tort case without supplying expert testimony.”), aff’d, 705 F. Appx. 126 (3d Cir. 2017); Ely v. Cabot Oil & Gas Corp., 2014 WL 12479991, at *10 (Mag. M.D. Pa. March 28, 2014) (“The law is well-established that claims for physical injury based upon alleged pollution or other torts generally require probative medical evidence.”), adopted, 2014 WL 12489767 (M.D. Pa. July 29, 2014); Kemmerer v. State Farm Insurance Co., 2004 WL 87017, at *3 (E.D. Pa. Jan. 19, 2004) (“In a case involving complex issues of causation not readily apparent to the fact finder, plaintiff must present admissible expert testimony to carry her burden.”); Fritz v Grossinger, 2009 WL 7039662 (Pa. C.P. Sept. 5, 2009) (“complex medical issues appertain to the determination of whether it was the remnant of the [medical device] . . . or some other cause that resulted in the alleged pain” and other injuries).

The same is true in Pennsylvania product liability litigation.  A “total lack of causation evidence absent the expert testimony . . . is a proper ground for summary judgment.”  Heller v. Shaw Industries, Inc., 167 F.3d 146, 165 (3d Cir. 1999) (applying Pennsylvania law).  “[E]xpert opinion on the effectiveness of the alternative design . . . [i]s required.”  Dunlap v. Federal Signal Corp., 194 A.3d 1067, 1073 (Pa. Super. 2018).

Pennsylvania law recognizes that proving the elements of these claims in complex tort cases often requires presentation of expert testimony. . . .  In other complex tort actions, such as product liability cases, courts have also opined that expert witnesses are often necessary to establish liability.  Further, courts recognize that there are consequences which flow from a failure to provide such proof.  Where a tort action turns on allegations of a technical nature relating to some alleged defect in a product, and the Plaintiff has failed to provide expert proof identifying the defect in the product or drawing a causal connection between that allegedly defective product and the Plaintiff’s injuries, courts have held that product liability and related negligence claims fail as a matter of law and must be dismissed.

Ruehl v. S.N.M. Enterprises, Inc., 2017 WL 5749560, at *1 (M.D. Pa. Nov. 28, 2017) (quoting American Power, LLC., v. Speedco Inc., 2017 WL 4084060, at *6 (M.D. Pa. Jan. 17, 2017) (citations omitted)).  See Nobles v. Staples, Inc., 150 A.3d 110, 120 (Pa. Super. 2016) (“exclusion of [plaintiff’s] expert made it impossible for [plaintiff] to prove” product liability even under a malfunction theory); Brandon v. Ryder Truck Rental, Inc., 34 A.3d 104, 110 (Pa. Super. 2011) (“an expert is necessary for [plaintiff] to prove his negligence claim against [defendant], and absent the testimony of a qualified expert, a jury’s verdict would be nothing more than conjecture”); Goldstein v. Phillip Morris, Inc., 854 A.2d 585, 589 (Pa. Super. 2004) (once plaintiff’s expert was “properly struck by the trial court . . . [plaintiff] had no means of establishing alleged specific defects in the [product]”); McCracken v. Ford Motor Co., 392 F. Appx. 1, 3 (3d Cir. 2010) (plaintiff “was required to support his claims of strict products liability and defective design with expert testimony”) (applying Pennsylvania law); Cabrera v. Ross Stores, LP, 646 F. Appx. 209 (3d Cir. 2016) (“expert testimony was necessary to establish the causation element of [plaintiff’s] suit”) (applying Pennsylvania law); Oddi v. Ford Motor Co., 234 F.3d 136, 159 (3d Cir. 2000) (“Inasmuch as [plaintiff’s] ‘defect expert’ does not survive Daubert scrutiny, the district court properly granted summary judgment to [defendants]”) (applying Pennsylvania law); Koplove v. Ford Motor Co., 795 F.2d 15, 18 (3d Cir. 1986) (“a rational jury could not find the defendant liable without some expert analysis of the available information which implicated it”) (applying Pennsylvania law); Bibbs v. SEPTA, 2012 WL 8704635, at *3 (Pa. Commw. April 13, 2012) (“Plaintiff was required to present expert testimony to establish that [product’s] defect . . . was the legal cause of Plaintiff’s injuries”); Hook v. Whiting Door Manufacturing Corp., 2019 WL 630324, at *6 (W.D. Pa. Feb. 14, 2019) (“where the issues in a products liability case are highly technical, expert testimony is necessary to assist the jury in understanding the claims”); White v. Home Depot, Inc., 2018 WL 2173960, at *4 (E.D. Pa. May 10, 2018) (summary judgment granted after defect expert excluded); McCracken v. R.J. Reynolds Tobacco Co., 2019 WL 635430, at *7 (E.D. Pa. Feb. 14, 2019) (quoting Lamar); Metil v. Core Distribution, Inc., 2018 WL 3707421, at *8 (W.D. Pa. Aug. 3, 2018) (“Absent [plaintiff’s] expert testimony relating to the cause of the accident and whether a design defect existed . . ., Plaintiff cannot support his theory of the case”); Bailey v. B.S. Quarries, Inc., 2017 WL 4366987, at *3 (M.D. Pa. Sept. 29, 2017) (“a product liability claim must be supported by expert witness testimony”); Hatcher v. SCM Group, Inc., 167 F. Supp.3d 719, 730 (E.D. Pa. 2016) (“without the expert report, there is no genuine dispute of material fact”); Inman v. General Electric Co., 2016 WL 5106939, at *9 (W.D. Pa. Sept. 20, 2016) (courts “routinely require plaintiffs to support their claims with expert testimony when the subject matter is highly technical and beyond the jury’s understanding”); Rabadi v. Great Wolf Lodge of the Poconos LLC, 2016 WL 4238638, at *5 (M.D. Pa. Aug. 9, 2016) (“Where, as here, a plaintiff fails to proffer the required expert evidence in response to a properly supported motion for summary judgment, summary judgment is appropriate.”) (citation and quotation marks omitted); Harris v. Oz Directional Drilling, Inc., 2016 WL 4578150, at *4 (Mag. M.D. Pa. June 30, 2016) (same as Ruehl), adopted, 2016 WL 4698635 (M.D. Pa. July 19, 2016); Webb v. Tahsin Industrial Corp., 2016 WL 454821, at *7 (M.D. Pa. Feb. 5, 2016) (“Lacking this expert evidence, Plaintiff’s claims must fail, and Defendant is entitled to an entry of summary judgment in its favor.”); Yoder v. Sportsman’s Guide, Inc., 2015 WL 7009547, at *12 (W.D. Pa. Nov. 12, 2015) (“the Court will enter summary judgment in Defendants’ favor as Plaintiffs do not present admissible expert evidence”); Rupert v. Ford Motor Co., 2015 WL 757402, at *9 (W.D. Pa. Feb. 23, 2015) (summary judgment granted after exclusion of plaintiff’s expert), aff’d, 640 F. Appx. 205 (3d Cir. 2016); Curry v. Royal Oak Enterprises, LLC, 2013 WL 3196390, at *7 (E.D. Pa. June 25, 2013) (“in a products liability case . . ., plaintiff must provide expert evidence to establish liability”) (citing Oddi); Ellis v. Beemiller, Inc., 910 F. Supp.2d 768, 774 (W.D. Pa. 2012) (“Expert testimony is required . . . if the subject matter is beyond the comprehension of the average juror”); Lamar v. Saks Fifth Ave., Inc., 2012 WL 12897909, at *2 (E.D. Pa. Oct. 23, 2012) (“under Pennsylvania law, in a case regarding the cause of pain or physical injury, a plaintiff must produce medical testimony”) (citing Hamil); Shecktor v. Louisville Ladder, Inc., 2012 WL 5052577, at *5 (M.D. Pa. Oct. 18, 2012) (“In the absence of that expert causation testimony . . . the Court is compelled to enter judgment in the Defendant’s favor.”); Westfield Insurance v. Detroit Diesel Corp., 2012 WL 1611311, at *4 (W.D. Pa. May 8, 2012) (“expert testimony is generally required in products liability cases where a defect is alleged, unless the issues are ‘simple’ and ‘within the range of comprehension of the average juror.’”); Mendoza v. Gribetz International, Inc., 2011 WL 2117610, at *3 (E.D. Pa. May 27, 2011) (“Expert testimony is generally required to sustain a products liability case.”) (citing Oddi); Maldonado v. Walmart Store No. 2141, 2011 WL 1790840, at *14 (E.D. Pa. May 10, 2011) (“Without the evidence of Plaintiff’s experts, Plaintiff has failed to offer sufficient evidence of causation”); Shannon v. Hobart, 2011 WL 442119, at *6 (E.D. Pa. Feb. 8, 2011) (“without expert testimony, a reasonable jury could not find from this evidence that the [product] contained a manufacturing or design defect that caused [plaintiff’s] injuries”); State Farm Fire & Casualty Co. v. Gopher Baroque Enterprises, Ltd., 2010 WL 5464767, at *6 (E.D. Pa. Dec. 29, 2010) (“Where the cause of an injury is arguably complex, a party must produce expert testimony on causation to survive a motion for summary judgment.”); Chubb v. On-Time Wildlife Feeders, 578 F. Supp.2d 737, 740 (M.D. Pa. 2008) (“Because a reasonable juror could not make a reasonable determination on [plaintiff’s] theory of liability without an expert witness, and [plaintiff’s] expert witness was precluded from testifying, there is no genuine issue of material fact to go to a jury.”); Thomas v. Hamilton Beach/Proctor-Silex, Inc., 2007 WL 2080485, at *7 (W.D. Pa. July 13, 2007) (“expert medical testimony is required to establish the requisite causal connection”); Marino v. Maytag Corp., 2005 WL 2403638, at *4 (W.D. Pa. Sept. 29, 2005) (“a juror could not look at the [plaintiff’s] evidence] without expert testimony to explain it”); Fabrizi v. Rexall Sundown, Inc., 2004 WL 1202984, at *12 (Mag. W.D. Pa. June 2, 2004) (“Where a plaintiff fails to present admissible expert testimony regarding causation, courts routinely have granted summary judgment in favor of the defendant.”) (citations omitted), adopted (W.D. Pa. June 24, 2004); Jones v. Toyota Motor Sales, USA, Inc., 282 F. Supp.2d 274, 277 (E.D. Pa. 2003) (“engineering, medical, and biomechanical analysis is not within the know-how of the ordinary layperson, and thus requires expert evidence”), aff’d, 94 F. Appx. 879 (3d Cir. 2004); Gower v. Savage Arms, Inc., 2002 WL 1833344, at *2 (E.D. Pa. June 12, 2002) (“Without expert testimony that the [product] was defective . . ., the plaintiffs cannot make out a design defect claim.”) (citations omitted); Booth v. Black & Decker, Inc., 166 F. Supp.2d 215, 223 (E.D. Pa. 2001) (“Without expert testimony, a reasonable jury could not find from this evidence that the [product] contained a manufacturing or design defect that defect caused the [accident].”); Rapp v. Singh, 152 F. Supp.2d 694, 707 (E.D. Pa. 2001) (“Absent such expert testimony, plaintiff cannot establish that the [product] was defective, or that [there is] a safer design.”); Chester Valley Coach Works, Inc. v. Fisher-Price, Inc., 2001 WL 1160012, at *13 (E.D. Pa. Aug. 29, 2001) (“Without his expert testimony, Plaintiffs lack sufficient evidence to establish the cause of the [accident].”); Pappas v. Sony Electonics, Inc., 136 F. Supp.2d 413, 427 (W.D. Pa. 2000) (“Absent [their expert’s] testimony, plaintiffs’ claims under Pennsylvania law cannot survive . . . summary judgment.”); Hodge v. Caterpillar, Inc., 1992 WL 98415, at *2 (E.D. Pa. April 30, 1992) (“expert opinion or analysis is a prerequisite to proof of a defective product”); Niklaus v. Vivadent, Inc., 767 F. Supp. 94, 96 (M.D. Pa. 1991) (“Pennsylvania law is clear that in a personal injury case when there is no obvious causal relationship between the accident and the injury, unequivocal medical testimony is necessary to establish the causal connection.”) (citation and quotation marks omitted); Blase v. Allied Signal, Inc., 36 Pa. D. & C.4th 491, 500 (Pa. C.P. 1996) (“complexities coupled with the intricacies of asbestos exposure require the presentation of expert medical testimony”).

The requirement for expert testimony is strongly enforced in Pennsylvania prescription medical product liability litigation.  In a medical device case, “the cause of [plaintiff’s] injury was something that could only be determined by the jury through expert medical testimony.”  Polett v. Public Communications, Inc., 126 A.3d 895, 931 (Pa. 2015).  “When the complexities of the human body place questions as to the cause of pain or injury beyond the knowledge of the average layperson, Pennsylvania requires expert testimony.”  Singer v. Eli Lilly & Co., 396 F. Appx. 715, 716 (2d Cir. 2010)) (applying Pennsylvania law).

In a case such as this one involving complex issues of causation not readily apparent to the finder of fact, plaintiff must present admissible expert testimony to carry her burden.  If [plaintiff’s] expert testimony cannot support both general and specific causation, summary judgment for the defendant must be granted.

Soldo v. Sandoz Pharmaceuticals Corp., 244 F. Supp.2d 434, 525 (W.D. Pa. 2003) (citing Heller).  Expert support is also mandatory in warning claims.

Expert testimony is admissible when it involves explanations and inferences not within the ordinary training, knowledge and experience of the jury. . . .  Certain questions cannot be determined intelligently merely from the deductions made and inferences drawn from practical experience and common sense.  On such issues, the testimony of one possessing special knowledge or skill is required in order to arrive at an intelligent conclusion.  In these matters, where laymen have no knowledge or training, the court and jury are dependent on the explanations and opinions of experts. . . .

Prescription drugs are likely to be complex medicines, esoteric in formula and varied in effect.  The terms and applications of a warning on such a drug, in order to have meaning, must be explained to the jury.  This is a subject so distinctively related to some science, profession, business or occupation as to be beyond the ken of the average layman.  Thus, we hold that in a complex products liability action such as this, expert testimony is required to determine whether the drug manufacturer’s warning to the medical community is adequate.

Dion v. Graduate Hospital, 520 A.2d 876, 881 (Pa. Super. 1987) (citations and quotation marks omitted).  See Demmler v. SmithKline Beecham Corp., 671 A.2d 1151, 1154 (Pa. Super. 1996) (“expert medical testimony is required to determine whether the drug manufacturer’s warning to the medical community is adequate”); Atkinson v. Ethicon, Inc., 2019 WL 3037304, at *4 (W.D. Pa. July 11, 2019) (“Plaintiffs’ claims fail because the claims require an expert report to establish causation”); In re Zoloft (Sertraline hydrochloride) Products Liability Litigation, 176 F. Supp.3d 483, 498 (E.D. Pa. 2016) (summary judgment granted; “Without admissible expert testimony . . ., Plaintiffs instead have cobbled together . . . biological plausibility, specific causation opinions based on an assumption that general causation has been established, and anecdotal evidence”) (footnote omitted), aff’d, 858 F.3d 787 (3d Cir. 2017); Young v. Pfizer, Inc., 2016 WL 1569472, at *3 (E.D. Pa. April 19, 2016) (Pennsylvania law “require[s] expert testimony when medical causation is at issue”); Kline v. Zimmer Holdings, Inc., 2015 WL 4077495, at *26 (W.D. Pa. July 6, 2015) (summary judgment granted; “the adequacy of a warning in prescription medical device cases generally must be proven by expert testimony”), aff’d, 662 F. Appx. 121 (3d Cir. 2016); Williams v. Wyeth, Inc., 2013 WL 3761107, at *2 (E.D. Pa. July 18, 2013) (“Plaintiff must provide expert medical testimony demonstrating that . . . Defendants’ products were a substantial factor in causing Plaintiff’s [injury]”); Fenelon v. Pfizer, Inc., 2012 WL 13173126, at *3 (S.D.N.Y. May 7, 2012) (“[w]ithout an expert, [plaintiff] cannot prove that [the drug] was the cause of [the] death”) (applying Pennsylvania law); Pusey v. Becton Dickinson & Co., 794 F. Supp.2d 551, 565 (E.D. Pa. 2011) (granting summary judgment after excluding plaintiff’s expert); Aaron v. Wyeth, 2010 WL 653984, at *9 (W.D. Pa. Feb. 19, 2010) (“the adequacy of a warning in prescription drug cases must be proven by expert testimony”); Mracek v. Bryn Mawr Hospital, 610 F. Supp.2d 401, 406 (E.D. Pa. 2009) (“without an expert report, [plaintiff] cannot establish that the [medical device] had a defect”), aff’d, 363 F. Appx. 925 (3d Cir. 2010); Dick v. American Home Products Corp., 2009 WL 1542773, at *4 (M.D. Pa. June 2, 2009) (“a plaintiff must produce expert medical testimony in order to prove that an allegedly defective product caused medical injury”); (lack of expert testimony was a “complete failure of proof as to this essential [causation] element of all of [plaintiff’s] claims [and] mandates the entry of summary judgment”); Perry v. Novartis Pharmaceuticals Corp., 564 F. Supp.2d 452, 473 (E.D. Pa. 2008) (“Because we have judged [plaintiff’s expert] evidence inadmissible . . ., we must also grant defendant’s motion for summary judgment.”); Soufflas v. Zimmer, Inc., 474 F. Supp.2d 737, 751 (E.D. Pa. 2007) (“Generally, the adequacy of a warning in prescription medical device cases must be proven by expert testimony.  This case is no different.”) (citing Demmler); Schmerling v. Danek Medical, Inc., 1999 WL 712591, at *10 (E.D. Pa. Sept. 10, 1999) (after experts excluded, “complete failure of proof as to [causation] of all of her claims mandates the entry of summary judgment”); O’Brien v. Sofamor, S.N.C., 1999 WL 239414, at *6 (E.D. Pa. March 30, 1999) (summary judgment granted after excluding plaintiff’s experts); Burton v. Danek Medical, Inc., 1999 WL 118020, at *5 (E.D. Pa. March 1, 1999) (“Absent admissible expert testimony that the [medical] device caused [their] injuries, Plaintiffs are unable to prevail on any of their claims.”); In re Risperdal Litigation, 2017 WL 3496520, at *5 (Pa. C.P. July 26, 2017) (“In the absence of expert testimony, Plaintiff cannot establish the warnings are inadequate.”) (citing Dion); Commonwealth v. Ortho-McNeil-Janssen Pharmaceuticals, Inc., 13 Pa. D. & C. 5th 187, 203 (Pa. C.P. 2010) (“expert medical testimony is required to determine whether the drug manufacturer’s warning to the medical community is adequate”); Lawrence v. Synthes, Inc., 2002 WL 32747667, at *24 (Pa. C.P. July 25, 2002) (“there can be no doubt that the medical cause of a complex condition such as is here presented requires expert evidence”), aff’d mem., 860 A.2d 1142 (Pa. Super. 2004).

Puerto Rico

The law in Puerto Rico holds that “a factfinder normally cannot find causation without the assistance of expert testimony to clarify complex medical and scientific issues that are more prevalent in medical malpractice cases than in standard negligence cases.”  Marcano Rivera v. Turabo Medical Center Partnership, 415 F.3d 162, 168 (1st Cir. 2005) (quoting Rojas-Ithier v. Sociedad Española de Auxilio Mutuo y Beneficiencia, 394 F.3d 40, 43 (1st Cir. 2005)) (applying Puerto Rico law).  “[T]he decisive consideration in determining the necessity of expert opinion evidence is whether the subject of inquiry is one of such common knowledge that persons of ordinary education could reach a conclusion as intelligently as the witness or whether, on the other hand, the matter is sufficiently beyond common experience that the opinion of an expert is required.”  Collazo-Santiago v. Toyota Motor Corp., 937 F. Supp. 134, 140 (D.P.R. 1996) (citation and quotation marks omitted), aff’d, 149 F.3d 23 (1st Cir. 1998).  See Velazquez v. Abbott Laboratories, 901 F. Supp.2d 279, 293 (D.P.R. 2012) (entering summary judgment on product liability claims because “plaintiffs have failed to introduce any expert testimony . . . to support their claims”).

The same rule applies to prescription medical products.  “[D]etermining when or if a given medication caused injuries when it was prescribed is the typical complex medical and scientific issue that . . . requires the assistance of a medical or scientific expert.”  Mercado-Velilla v. Asociacion Hospital del Maestro, 902 F. Supp.2d 217, 239 (D.P.R. 2012) (citation and quotation marks omitted).  See In re Bausch & Lomb Inc. Contacts Lens Solution Products Liability Litigation, 693 F. Supp.2d 515, 520 (D.S.C. 2010) (“this case involves complex medical causation questions . . . that are outside the realm of ‘common experience.’  Therefore, expert testimony is required under Puerto Rico law.”), aff’d, 429 F. Appx. 249 (4th Cir. 2011) (applying Puerto Rico law).

Rhode Island

Rhode Island precedent “is well settled that expert testimony is required to establish any matter that is not obvious to a lay person and thus lies beyond common knowledge.”  Rhode Island Resource. Recovery Corp. v. Restivo Monacelli LLP, 189 A.3d 539, 547 (R.I. 2018) (quoting Jessup & Conroy, P.C. v. Seguin, 46 A.3d 835, 839 (R.I. 2012)).  See Almonte v. Kurl, 46 A.3d 1, 18 (R.I. 2012) (same).  “[M]atters concerning [diseases] and [drug] therapy are not so obvious that the need for expert testimony is obviated.”  Young v. Park, 417 A.2d 889, 893 (R.I. 1980).

Thus, in product liability cases, the “we do not hesitate to conclude that the existence of a causal relationship between a particular toxin and its effect on the human body would have to be established through expert testimony.”  Mills v. State Sales, Inc., 824 A.2d 461, 468 (R.I. 2003).  Even as to products that “average lay persons use . . . every day, . . . only an expert who understands the[ir] mechanics . . . could understand and explain the [product] and whether a defect proximately caused an injury.”  Olshansky v. Rehrig International, 872 A.2d 282, 287 (R.I. 2005) (abrogated on other grounds, Cruz v. DaimlerChrysler Motors Corp., 66 A.3d 446 (R.I. 2013)).  See Hartford Insurance Co. v. General Electric Co., 526 F. Supp.2d 250, 260 (D.R.I. 2007) (“In the absence of such expert evidence . . ., Plaintiffs have not otherwise identified competent evidence upon which a reasonable jury could find that the alleged defect in the [product] was the proximate cause”).

South Carolina

“The general rule in South Carolina is that where a subject is beyond the common knowledge of the jury, expert testimony is required.”  Babb v. Lee County Landfill SC, LLC, 747 S.E.2d 468, 481 (S.C. 2013).  “[W]hen the medical question is a complicated one and likely to carry the fact-finding body into realms which are more properly within the province of medical experts,” “the subject is one for experts or skilled witnesses alone.”  Herndon v. Morgan Mills, Inc., 143 S.E.2d 376, 384 (1965).  “If [a plaintiff] is attempting to establish causation of a medically complex condition, however, expert medical testimony is required.”  Smith v. Michelin Tire Co., 465 S.E.2d 96, 97 (S.C. App. 1995).

Likewise, in South Carolina product liability cases, “expert evidence is required where a factual issue must be resolved with scientific, technical, or any other specialized knowledge.”  Watson v. Ford Motor Co., 699 S.E.2d 169, 175 (S.C. 2010).

Whether expert testimony is required is a question of law.  We have little trouble concluding as a matter of law that the [plaintiffs’] claim is one such case because it involves complex issues of computer science. . . .  [T]the design and structure of the software . . . is beyond the ordinary understanding and experience of laymen.  Hence, [plaintiffs] must support their allegations with expert testimony, and without it, their claims are subject to dismissal.

Graves v. CAS Medical Systems, Inc., 735 S.E.2d 650, 659 (S.C. 2012) (citations omitted).  See Oglesby v. General Motors Corp., 190 F.3d 244, 251 (4th Cir. 1999) (“Without [expert] testimony, [plaintiff] failed to meet his burden of proof.”) (applying South Carolina law); Green v. Bradley Co., 2017 WL 4012298, at *7 (D.S.C. Sept. 12, 2017) (“Absent the now-excluded testimony of [her expert], Plaintiff is unable to establish either the existence of a defect in the [product] at issue, or that a defect was the proximate cause of her injury − both essential elements of her claim.”), aff’d, 771 F. Appx. 184 (4th Cir. 2019); Morris v. Dorma Automatics Inc., 2013 WL 212587, at *6 (D.S.C. Jan. 18, 2013) (summary judgment granted where plaintiff “did not offer expert testimony”), aff’d, 537 F. Appx. 254 (4th Cir. 2013); Hickerson v. Yamaha Motor Corp., U.S.A., 2016 WL 4367141, at *4 (D.S.C. Aug. 16, 2016) (“without such expert testimony here to support Plaintiff’s claims of inadequate warnings, it would be difficult for this court to accept that a jury could find that the warnings . . . inadequate”), aff’d, 882 F.3d 476 (4th Cir. 2018); Stewart v. AT & T Mobility LLC, 2011 WL 3626654, at *5 (Mag. D.S.C. July 21, 2011) (“Without such admissible expert testimony to support a plaintiff’s theory of causation, the defendant is entitled to summary judgment.”), adopted, 2011 WL 3626641 (D.S.C. Aug. 17, 2011); Owens v. Hertz Equipment Rental Corp., 2010 WL 11534370, at *2 (D.S.C. Dec. 23, 2010) (“the use, operation, and maintenance of the [product] are technical matters which go beyond the scope of a lay person’s knowledge.  Therefore, Plaintiff must bring forth expert testimony to establish his burden of proof.”); Morehouse v. Louisville Ladder Group LLC, 2004 WL 2431796, at *9 (D.S.C. June 28, 2004) (“In the absence of [expert] testimony, Plaintiff is unable to establish that Defendant’s [product] was defective or that such defect caused Plaintiff’s accident.”).

Specifically, “[u]nder South Carolina law, in a [prescription medical product liability] case where a medical causation issue is not one within the common knowledge of the layman, the plaintiff must present medical expert testimony in order to establish causation.  Jones v. American Cyanamid Co., 139 F.3d 890, 1998 WL 116171, at *3 (4th Cir. 1998) (citation and quotation marks omitted) (applying South Carolina law).  “To establish defect and unreasonable danger in a medically complex [product liability] case, plaintiff must come forward with relevant and reliable expert testimony on these issues.”  King v. Stryker Corp., 2012 WL 12981763, at *4 (D.S.C. April 3, 2012) (citation and quotation marks omitted).  “Where a medical causal relation issue is not one within the common knowledge of the layman, proximate cause cannot be determined without expert medical testimony.”  In re Bausch & Lomb Inc. Contacts Lens Solution Products Liability Litigation, 693 F. Supp.2d 515, 518 (D.S.C. 2010), aff’d, 429 F. Appx. 249 (4th Cir. 2011).

[A] plaintiff [who] has not come forward with any proposed expert to offer biomechanical testimony . . . has no means of establishing how any proposed, theoretical modifications to the design of the [device] would function once implanted in the human body.  Without testimony necessary to fill this evidentiary gap, plaintiff cannot, as a matter of law, establish that the [device] was defective or unreasonably dangerous.

Disher v. Synthes (U.S.A.), 371 F. Supp.2d 764, 770 (D.S.C. 2005).  “Expert testimony is required where the claimant is ‘attempting to establish causation of a medically complex condition.’”  Jones v. Danek Medical, Inc., , 1999 WL 1133272, at *4 (D.S.C. Oct. 12, 1999) (emphasis original) (quoting Smith v. Michelin).  See Phelan v. Synthes (U.S.A.), 35 F. Appx. 102, 108-10 (4th Cir. 2002) (affirming summary judgment and exclusion of plaintiff’s expert); McClure v. Wyeth, 2012 WL 952856, at *1 (D.S.C. March 20, 2012) (“Under South Carolina law, expert testimony is necessary to establish causation for cases involving a complex medical condition”) (citing Smith); Jones v. Danek Medical, Inc., 1999 WL 1133272, at *4–5 (D.S.C. Oct. 12., 1999) (“granting summary judgment” when plaintiff failed to produce qualified expert to show causation in defective medical device case).

South Dakota

In South Dakota, “expert testimony is required when the issue falls outside the common experience of a jury.”  Burley v. Kytec Innovative Sports Equipment, Inc., 737 N.W.2d 397, 407 (S.D. 2007) (citing Caldwell v. John Morrell & Co., 489 N.W.2d 353 (S.D. 1992)).  “[A]bsent expert testimony, there is no basis for the jury to evaluate the actions of an ordinary prudent person.”  Id. at 408-09 (citation omitted).

Medical opinion on causation of physical injury is unnecessary only if the cause and effect are so immediate, direct and natural to common experience as to obviate any need for an expert medical opinion.  On the other hand, when symptoms are more separated in time from the accident, the causal relationship becomes more tenuous, necessitating expert testimony to prove causation.

Hanson v. Big Stone Therapies, Inc., 916 N.W.2d 151, 162 (S.D. 2018) (citations and quotation marks omitted).

Further, “in attempting to establish the elements of products liability, . . . [e]xpert testimony is generally necessary to establish elements of negligence and strict liability.”  Nationwide Mutual Insurance Co. v. Barton Solvents, Inc., 855 N.W.2d 145, 151 (S.D. 2014) (citation omitted).  “Plaintiff bore the burden to prove both liability and causation in a products liability action and expert testimony was necessary to provide ‘an evidentiary basis’ to successfully resist summary judgment.”  Cooper v. Brownell, 923 N.W.2d 821, 825 (S.D. 2019) (quoting Barton Solvents).  See Lindholm v. BMW of North America, LLC, 202 F. Supp.3d 1082, 1094 (D.S.D. 2016) (“it is not patently obvious that the accident would not have happened in the absence of a defect, and thus expert testimony is necessary to support Plaintiffs’ claims”), aff’d, 862 F.3d 648 (8th Cir. 2017); O’Neal v. Remington Arms Co., L.L.C., 2016 WL 1465351, at *3 (D.S.D. April 14, 2016) (Whether a plaintiff’s theory is based on strict liability or negligence, expert testimony is generally necessary to establish that a product is defective and that the defect proximately caused the plaintiff’s injury.”); Donat v. Trek Bicycle Corp., 2016 WL 297436, at *5 (D.S.D. Jan. 22, 2016) (“expert testimony is required when there is a complicated causation issue in a products liability case”); Jensen v. Hy-Vee, Corp., 2011 WL 1832997, at *4, 9 (D.S.D. May 13, 2011) (“expert testimony is required to help the jury determine whether . . . the alleged design defect caused [plaintiff’s] injuries” (citing Burley); “expert testimony establishing a causal connection between the lack of warning and [plaintiff’s] injuries is needed”).

Tennessee

Tennessee precedent requires that “[m]edical causation and permanency of an injury must be established in most cases by expert medical testimony.”  Thomas v. Aetna Life & Casualty Co., 812 S.W.2d 278, 283 (Tenn. 1991) (citations omitted).  “Typically, causation is established through expert medical testimony.”  Conner Brothers Excavating Co. v. Long, 98 S.W.3d 656, 660 (Tenn. 2003) (citing Thomas).

[W]hen the cause of an injury is not within the common knowledge of lay persons, expert medical evidence . . . is required.  Where an injury is complex or closely related to a pre-existing condition, expert evidence is critically important.  In these circumstances, the fact-finder cannot make a rational determination regarding whether the [defendant’s actions] caused the injury.

Austin v. Sneed, 2007 WL 3375335, at *11 (Tenn. App. Nov. 13, 2007) (citations omitted).  See Jones v. Firestone Tire & Rubber, 2001 WL 432528, at *3 (Tenn. April 27, 2001) (holding, in an asbestos exposure case, that “in all but the most obvious cases . . ., expert testimony is required to establish causation.  Proof of causation in this case must be shown by expert testimony.”) (citing Thomas).

In product liability cases, “[m]odern case law requires expert medical testimony to establish causation in cases where the plaintiff has suffered a complex injury.”  Smith v. General Motors Corp., 376 F. Supp.2d 664, 667 (W.D. Va. 2005), aff’d, 179 F. Appx. 890 (4th Cir. 2006) (for reasons stated by trial court) (applying Tennessee law).  To “establish[] the unreasonable dangerousness of a complex product about which an ordinary consumer has no reasonable expectation . . ., [t]he plaintiff must offer expert testimony.”  Brown v. Raymond Corp., 432 F.3d 640, 644 (6th Cir. 2005) (citation and quotation marks omitted).  With respect to a complex product, “without admissible expert testimony on causation and product defect, no reasonable jury could find for [plaintiff] because, under Tennessee law, expert testimony is required to establish liability in cases alleging manufacturing and design defects.”  Pride v. BIC Corp., 218 F.3d 566, 580 (6th Cir. 2000) (applying Tennessee law).  “Under Tennessee law, a plaintiff must provide admissible expert testimony as to both causation and product defect in order to prove liability in a products action. . . .  Moreover, under Tennessee law, medical causation must be established by expert testimony.”  Tomazin v. Lincare, Inc., 2015 WL 4545658, at *12 (M.D. Tenn. July 27, 2015) (citations omitted).  Thus, “[i]t is settled law that plaintiffs in a toxic tort case must present competent expert testimony . . . that links the individual plaintiff’s harm to the toxic substance allegedly causing the plaintiff’s injury.”  Spencer v. Synair Corp., 2005 WL 1719904, at *6 (E.D. Tenn. July 22, 2005) (quoting Nelson v. Tennessee Gas Pipeline Co., 2002 WL 1397253, at *2 (W.D. Tenn. June 11, 2002)).  See Whaley v. Rheem Manufacturing Co., 900 S.W.2d 296, 301 (Tenn. App. 1995) (plaintiff required expert testimony to demonstrate defect because the “workings of [the product] are beyond the common knowledge of laymen.”); Johnson v. Manitowoc Boom Trucks, Inc., 484 F.3d 426, 429 (6th Cir. 2007) (“expert testimony about the prudence of the decision to market becomes essential to [the] plaintiff’s case in chief” “because it involves establishing the unreasonable dangerousness of a complex product”) (citation and quotation marks omitted) (applying Tennessee law); Downs v. Perstorp Components, Inc., 26 F. Appx. 472, 477 (6th Cir. 2002) (“without admissible expert testimony on causation, no reasonable jury could find for plaintiffs because Tennessee law requires proof of causation for both strict liability and negligence actions”) (applying Tennessee law); Sanford v. L’Oreal USA S/D, Inc., 2017 WL 2376922, at *2 (M.D. Tenn. June 1, 2017) (where plaintiff “has failed to submit any testimony from a medical expert . . . there exists no material factual dispute regarding the cause of” her injuries); Coffey v. Dowley Manufacturing, Inc., 187 F. Supp.2d 958, 972 (M.D. Tenn. 2002) (“Plaintiffs will be unable to make out a claim for products liability without the use of an expert.  This product is simply too complex and too unfamiliar to ordinary consumers.”), aff’d, 89 F. Appx. 927 (6th Cir. 2003).

Prescription medical products are “complex products” under Tennessee law, requiring expert testimony.  In Jastrebski v. Smith & Nephew Richards, Inc., 1999 WL 144935 (Tenn. App. March 18, 1999), the court held:

Plaintiff’s testimony cannot substitute for the expert testimony required to establish a causal connection between an alleged defect in the product and a specific injury.  The product in dispute is a technically complex prescription medical device, and expert testimony is required to establish the causal connection between the alleged defect in the device and Plaintiff’s claimed injuries.

Id. at *6.  Jastrebski cited Fulton v. Pfizer Hospital Products Group, Inc., 872 S.W.2d 908, 912 (Tenn. App. 1993), which rejected use of res ipsa loquitur, holding that, where “the product in dispute is a technically complex medical device . . . expert testimony is required.”  Id. at 912.  See King v. Danek Medical, Inc., 37 S.W.3d 429, 449, 450, 461 (Tenn. App. 2000) (affirming summary judgment after concluding that plaintiff’s experts “failed to establish” either that “the defendants’ devices were unreasonably dangerous” or any “defective condition of the [medical device] implanted into the plaintiffs or causation”); Ward v. Cook, Inc., 2015 WL 3556060, at *2 (S.D.W. Va. June 4, 2015) (“medical causation must be established by testimony from a medical expert”) (applying Tennessee law); Shannon v. Apria Healthcare, Inc., 2011 WL 873458, at *5 (M.D. Tenn. March 4, 2011) (medical device case; “[w]ithout expert medical proof . . ., the factual allegations made by Plaintiff . . . cannot be sustained as a matter of law”); In re Aredia & Zometa Products Liability Litigation, 2009 WL 8638121, at *1 (M.D. Tenn. Aug. 13, 2009) (“Whether the warnings were adequate to warn a physician of the possibility that the drug might be causing the condition experienced must be presented through the testimony of an expert.”) (citations omitted);

Texas

“The general rule” in Texas “has long been that expert testimony is necessary to establish causation as to medical conditions outside the common knowledge and experience of jurors.”  Guevara v. Ferrer, 247 S.W.3d 662, 665 (Tex. 2007).  “[W]hen the causal link is beyond the jury’s common understanding, expert testimony is necessary.”  Alexander v. Turtur & Associates., Inc., 146 S.W.3d 113, 119-20 (Tex. 2004).  “The determination whether expert testimony is necessary is . . . a question of law.”  FFE Transportation Services, Inc. v. Fulgham, 154 S.W.3d 84, 89 (Tex. 2004).  Summing up:

Expert testimony is required when an issue involves matters beyond jurors’ common understanding.  Proof other than expert testimony will support a jury finding only when the jurors’ common understanding and experience will allow them to make that finding with reasonable probability.  . . .  The plaintiffs’ causation theory in this case is complex . . . [and] [w]e therefore hold that the plaintiffs must have supported their causation theory with expert testimony and objective proof.

Gharda USA, Inc. v. Control Solutions, Inc., 464 S.W.3d 338, 348 (Tex. 2015) (citations and quotation marks omitted).  See Bright v. Simpson, 2019 WL 1941885, at *4 (Tex. App. April 30, 2019) (“Without expert medical testimony, the evidence is legally insufficient to support a finding that the collision caused all of [plaintiff’s] damages.”); Zamora v. Champion Cooler Corp., 2018 WL 507362, at *2 (Tex. App. Jan. 23, 2018) (“expert testimony is necessary to establish causation regarding medical conditions outside the common knowledge and experience of jurors”); Cerny v. Marathon Oil Corp., 480 S.W.3d 612, 620 (Tex. App. 2015) (“The requirement of expert testimony is equally obvious in this case where [plaintiffs’] claims arise out of the alleged emissions and migration of hazardous substances”); Oncor Electric Delivery Co., LLC v. Southern Foods Group, LLC, 444 S.W.3d 699, 705 (Tex. App. 2014) (“Expert testimony is required when an issue involves matters beyond jurors’ common understanding.”) (citing Tamez); Dickerson v. State Farm Lloyd’s Inc., 2011 WL 3334964, at *14 (Tex. App. Aug. 3, 2011) (affirming both expert exclusions and summary judgment); Plunkett v. Connecticut General Life Insurance Co., 285 S.W.3d 106, 121 (Tex. App. 2009) (affirming summary judgment in toxic exposure case after affirming exclusion of plaintiffs’ experts); Brookshire Brothers, Inc. v. Smith, 176 S.W.3d 30, 36 (Tex. App. 2004) (“When a lay person’s general experience and common sense will not enable that person to determine causation, expert testimony is required.”); Feria v. Dynagraphics Co., 2004 WL 500869, at *9 (Tex. App. March 15, 2004) (“Because we find that the court did not abuse his discretion in excluding the expert witnesses tendered by [plaintiff], there was no evidence of causation presented to the court to defeat the defendants’ motions for summary judgment.”); Smith v. Southwest Bell Telephone Co., 101 S.W.3d 698, 702 (Tex. App. 2003) (“Proof that an injury to a specific body part extends to and affects the body generally must be supported by expert medical testimony and is not within the general experience of the jury.”).

Likewise, “[w]e have consistently required expert testimony and objective proof to support a jury finding that a product defect caused the plaintiff’s condition.”  Gharda, 464 S.W.3d at 348 (citations and quotation marks omitted).  In product liability cases, “[w]hether expert testimony is required depends on whether the issue involves matters beyond the general experience and common understanding of laypersons.”  Mack Trucks, Inc. v. Tamez, 206 S.W.3d 572, 583 (Tex. 2006).  “If juries were generally free to infer a product defect and injury causation from an accident or product failure alone, without any proof of the specific deviation from design that caused the accident, expert testimony would hardly seem essential.  Yet we have repeatedly said otherwise.”  Ford Motor Co. v. Ledesma, 242 S.W.3d 32, 42-43 (Tex. 2007) (citations omitted).  Texas law has “consistently required competent expert testimony and objective proof that a defect caused the [accident].”  Nissan Motor Co. Ltd. v. Armstrong, 145 S.W.3d 131, 137 (Tex. 2004).  Thus, “expert testimony is crucial in establishing that the alleged design defect caused the injury.”  Sims v. Kia Motors, Inc., 839 F.3d 393, 409 (5th Cir. 2016) (footnote omitted) (applying Texas law).

This case illustrates the type of complex causation theory that requires expert testimony and objective proof. . . .  Without such an expert, the plaintiffs have not met their burden of production under Texas law.  The plaintiffs’ failure to produce a fire expert who can identify the cause of the fire is therefore fatal to their success.

Smith v. Chrysler Group, L.L.C., 909 F.3d 744, 751-52 (5th Cir. 2018) (citations and footnotes omitted) (applying Texas law).  See BIC Pen Corp. v. Carter, 346 S.W.3d 533, 542 (Tex. 2011) (“Expert testimony is generally required in manufacturing defect cases to prove that the specific defect caused the accident.”); PHI, Inc. v. LeBlanc, 2016 WL 747930, at *8 (Tex. App. Feb. 25, 2016) (“whether [the product’s] design was defective involves a matter beyond the jurors’ common understanding, [so] we conclude that as a matter of law expert testimony was required”); Starr v. A.J. Struss & Co., 2015 WL 4139028, at *6 (Tex. App. July 9, 2015) (“Expert testimony is particularly necessary in toxic-tort and chemical-exposure cases, in which medically complex diseases and causal ambiguities compound the need for expert testimony.”) (citations omitted); iLight Technologies, Inc. v. Clutch City Sports & Entertainment, L.P., 414 S.W.3d 842, 851 (Tex. App. 2013) (“Expert testimony is generally required in manufacturing defect cases to prove that the specific defect caused the accident.”); Mata v. Energy Absorption Systems, LLC, 2011 WL 1233584, at *4 (Tex. App. March 31, 2011) (“competent expert testimony and objective proof that a defect caused the harm is required”); Lyon v. ATICO International USA, Inc., 2009 WL 1800820, at *2 (Tex. App. June 24, 2009) (“causation is not within a layperson’s general experience and common understanding; thus, expert testimony was required to establish a manufacturing defect”); Driskill v. Ford Motor Co., 269 S.W.3d 199, 205 (Tex. App. 2008) (“Because [plaintiffs] presented no expert testimony on causation . . ., there is less than a scintilla of evidence that the [product] was the cause-in-fact of the [incident] in this case.”); Poteet v. Kaiser, 2007 WL 4371359, at *3 (Tex. App. Dec. 13, 2007) (“a determination of causation in this case requires expert testimony”); Brown v. Rreef Management Co., 2007 WL 1829725, at *1 (Tex. App. June 27, 2007) (“Expert testimony is particularly necessary in chemical-exposure cases, in which medically complex diseases and causal ambiguities compound the need for expert testimony.”) (citation omitted); Hair v. Church & Dwight Co., 2004 WL 1615833, at *2 (Tex. App. July 20, 2004) (“Because [plaintiff] did not direct the trial court to any expert testimony that [defendant’s] product caused his injury, he did not raise a fact question on proximate cause.”); Sweeney v. Geon Co., 2002 WL 58223, at *4 (Tex. App. Jan. 17, 2002) (affirming summary judgment; “proving causation [here] requires expert testimony” because “causation of injuries from exposure to toxic chemicals is not readily ascertainable from general experience and common sense”); City of Dallas v. Furgason, 2007 WL 2703134, at *2 (Tex. App. Sept. 18, 2007) (“the record does not contain any expert testimony regarding either general or specific causation.  Thus, we conclude the evidence is legally insufficient to show the causal connection”); Norman v. Grove Cranes U.S., L.L.C., 750 F. Appx. 269, 273 (5th Cir. 2018) (“numerous intermediate Texas courts and federal district courts have granted judgments in favor of defendants where no admissible expert testimony was offered to prove the existence of a safer alternative design”) (citations omitted) (applying Texas law); Velasquez v. EAN Holdings, LLC, 2018 WL 5924037, at *9 (N.D. Tex. Nov. 13, 2018) (“Without expert testimony, Plaintiff has provided no evidence supporting his claim that the alleged condition of the [product], . . . proximately caused his injury.”); Carter v. Southstar Management, LLC, 2018 WL 5281791, at *5 (S.D. Tex. Oct. 24, 2018) (summary judgment granted “[b]ecause toxic tort cases require expert evidence of both general and specific causation, and there is no expert evidence on causation”); Deeds v. Whirlpool Corp., 2017 WL 3437772, at *13 (S.D. Tex. Aug. 10, 2017) (“Plaintiffs must have an expert witness for the defective product claims.”), aff’d, 764 F. Appx. 407 (5th Cir. 2019); Samuell v. Toyota Motor Corp., 2015 WL 1925902, at *5 (W.D. Tex. April 27, 2015) (“expert testimony is essential to both the existence of the defect and to its causation of injury”); Sedgwick v. BP Products North America, Inc., 2014 WL 6911543, at *3 (S.D. Tex. Nov. 4, 2014) (“Plaintiff’s claim is beyond the general experience of laypersons, and therefore requires expert testimony to establish both general and specific causation.”) (citation omitted); Romo v. Ford Motor Co., 798 F. Supp.2d 798, 809 (S.D. Tex. 2011) (“Courts applying Texas law in products liability actions have frequently required expert testimony for both defect and causation.”); In re Ford Motor Co. Speed Control Deactivation Switch Products Liability Litigation, 2011 WL 2518776, at *3 (E.D. Mich. March 29, 2011) (plaintiff’s expert’s “testimony is stricken, [and] Plaintiff does not have any evidence to support her burden of proving that a defective [product] caused the [incident]”) (applying Texas law); Kallassy v. Cirrus Design Corp., 2006 WL 1489248, at *4 (N.D. Tex. May 30, 2006) (“Without expert testimony, [plaintiff] cannot prove the existence of defect, an element essential to his strict product liability claims.”), aff’d, 265 F. Appx. 165 (5th Cir. 2008); Sigurdson v. Ford Motor Co., 2006 WL 417502, at *3 (S.D. Tex. Feb. 21, 2006) (“In light of the complete absence of expert testimony . . ., Defendant is entitled to summary judgment.”); Robinson v. Proctor & Gamble Distributing Co., 2004 WL 3019092, at *2 (N.D. Tex. Dec. 30, 2004) (“Because this Court struck Plaintiff’s expert on causation, she is left without any expert testimony”; “to the extent Plaintiff seeks damages for her [condition], she will be barred from recovery”).

In particular, “expert testimony is needed to satisfy the reasonable medical probability standard for establishing a causal link” in Texas prescription medical product cases.  Anderson v. Siemens Corp., 335 F.3d 466, 475 (5th Cir. 2003) (applying Texas law).  “Evidence of general causation in a drug case must be established through expert testimony.”  Wells v. SmithKline Beecham Corp., 2009 WL 564303, at *5 (W.D. Tex. Feb. 18, 2009), aff’d, 601 F.3d 375 (5th Cir. 2010).  “Texas courts have regarded expert testimony on causation as particularly vital in cases involving complex medical devices and medical diagnoses.”  Lewis v. Johnson & Johnson, 601 F. Appx. 205, 211 (4th Cir. 2015) (applying Texas law).

[E]xpert testimony is necessary to establish that Defendant’s alleged negligence in designing, assembling, inspecting, and maintaining the [medical device] (as well as failing to warn Plaintiff) proximately caused Plaintiff’s injuries.  Therefore, Plaintiff cannot escape his burden of offering expert testimony to support his causation theory merely by pleading that this is a case of simple negligence, rather than strict products liability.  In sum, Plaintiff’s failure to designate an expert to testify concerning proximate causation of his injuries is fatal to his case.

Morris v. National Seating & Mobility, Inc., 2019 WL 2343020, at *5 (Mag.W.D. Tex. June 3, 2019) (citations omitted).  See Burroughs Wellcome Co. v. Crye, 907 S.W.2d 497, 499-500 (Tex. 1995) (reversing verdict after excluding plaintiff’s expert); Johnson & Johnson v. Batiste, 2015 WL 6751063, at *4 (Tex. App. Nov. 5, 2015) (“proving the existence of a design defect requires competent expert testimony and objective proof that the defect the plaintiff has identified caused the injury”); Schronk v. Laerdal Medical Corp., 440 S.W.3d 250, 265 (Tex. App. 2013) (given “that the trial court did not err in excluding the testimony of [plaintiff’s experts], we cannot conclude that the trial court erred in granting summary judgment” to medical device manufacturer); Ethicon Endo-Surgery, Inc. v. Gillies, 343 S.W.3d 205, 212 (Tex. App. 2011) (since “the standard of care in marketing a specialized medical device requiring specialized technique for use is not within the experience of laymen, we must also conclude expert testimony was required to prove negligent marketing of such a device”); Minnesota Mining & Manufacturing Co. v. Atterbury, 978 S.W.2d 183, 203 (Tex. App. 1998) (“the plaintiffs’ experts failed to offer any reliable evidence of general causation” and “[i]n the absence of such evidence, the award of actual damages to the plaintiffs must therefore be reversed.”); Emerson v. Johnson & Johnson, 2019 WL 764660, at *3 (S.D. Tex. Jan. 22, 2019) (medical device “allegations involve complex and technical medical issues beyond jurors’ common understanding, knowledge, and experience, and therefore expert testimony on causation is required”); Tsao v. Ferring Pharmaceuticals, Inc., 2018 WL 3589097, at *7 (Mag. S.D. Tex. April 17, 2018) (“the nature, function, and potency of [a drug] . . . and its impact on [a] medically complicated process . . . are beyond the common knowledge and experience of laypersons”), adopted, 2018 WL 3589082 (S.D. Tex. June 13, 2018); Samuel v. Johnson & Johnson, 2015 WL 10793724, at *4 (E.D. Tex. Aug. 14, 2015) (expert testimony required to prove causation because “the nature and function of the prescription drug . . .  are outside the common understanding of a layperson.”); Christian v. Cook Inc., 2015 WL 3557242, at *2 (S.D.W. Va. June 4, 2015) (“the plaintiffs here must offer a medical expert . . . to testify on causation”) (citing Guevara) (applying Texas law); Gutierrez v. Arrow International, Inc., 2011 WL 13324082, at *9 (W.D. Tex. May 17, 2011) (“Absent expert testimony, [plaintiff] cannot raise a genuine issue of material fact that [the device] manufactured by the . . . defendants . . . caused or could cause him harm”); Wells v. SmithKline Beecham Corp., 2009 WL 564303, at *5 (W.D. Tex. Feb. 18, 2009) (“Evidence of general causation in a drug case must be established through expert testimony.”), aff’d, 601 F.3d 375 (5th Cir. 2010); Hohmann v. Shire Pharmaceuticals, 2008 WL 11388683, at *3 (S.D. Tex. July 3, 2008) (“Plaintiffs are required to produce expert testimony to satisfy the element of causation common to all of their claims”); In re Diet Drugs (Phentermine/Fenfluramine/Dexfenfluramine) Products Liability Litigation, 2008 WL 355517, at *2 (E.D. Pa. Feb. 8, 2008) (“Expert testimony regarding causation is therefore required”; without an expert, “Plaintiff has put forth no evidence that her alleged injury was caused by [defendant]s’ diet drugs”) (applying Texas law); Snee v. Zimmer, Inc., 2005 WL 8161446, at *2 (E.D. Tex. Sept. 16, 2005) (medical device case involves “complex issues of causation, undoubtedly requiring expert testimony and scientific analysis”); Kimble v. Danek Medical, Inc., 2000 WL 1468675, at *3 (S.D. Tex. Sept. 7, 2000) (“the effect of the implantation of a [medical] device . . . is not a matter of common knowledge or within the experience of a layperson” so “expert testimony is required on the issues of medical causation”) (citation and quotation marks omitted); Nobles v. Sofamor, S.N.C., 81 F. Supp.2d 735, 740 (S.D. Tex. 1999) (with plaintiff’s expert excluded, there is“no fact issue as to the presence of an instrument defect that caused [plaintiff’s] injury.”); Conger v. Danek Medical, Inc., 1998 WL 1041331, at *7 (N.D. Tex. Dec. 14, 1998) (exclusion of plaintiff’s experts means “Plaintiffs have not raised a genuine fact issue as to causation”); Leigh v. Danek Medical, Inc., 1998 WL 1041329, at *6 (N.D. Tex. Dec. 14, 1998) (with plaintiff’s experts excluded, “it is clear that plaintiff cannot raise a genuine issue of material fact as to causation”); Kelley v. American Heyer-Schulte Corp., 957 F. Supp. 873, 884 (W.D. Tex. 1997)  (“Due to . . . exclusion of expert testimony, the Plaintiff can present no evidence that [defendants’ devices] cause” the alleged injuries).

Utah

Utah law requires expert testimony on “scientific matters beyond the capacity of an ordinary juror.”  Graves v. North. Eastern. Services, Inc., 345 P.3d 619, 627 (Utah 2015).

[Where] the standard of care and the causal link between the negligence and the injury are usually not within the common knowledge of the lay juror, testimony from relevant experts is generally required in order to ensure that factfinders have adequate knowledge upon which to base their decisions.

Bowman v. Kalm, 179 P.3d 754, 755–56 (Utah 2008) (citation omitted).  “This is because the average lay juror is ill-equipped to sift through complicated medical evidence.”  Harris v. ShopKo Stores, Inc., 308 P.3d 449, 459 (Utah 2013).

In any type of case, “[i]n the absence of expert assistance, jurors would not likely possess the information or understanding necessary to make such assessments” involving “nuanced analysis of matters beyond the normal experience of the average layperson.”  Jenkins v. Jordan Valley Water Conservancy Dist., 321 P.3d 1049, 1053-54 (Utah 2013).  “[W]here the injury involves obscure medical factors which are beyond an ordinary lay person’s knowledge, necessitating speculation in making a finding, there must be expert testimony that the negligent act probably caused the injury.”  Fox v. Brigham Young University, 176 P.3d 446, 451–52 (Utah App. 2011) (citations and quotation marks omitted).  Moreover, “[i]t is only in the most obvious cases that a plaintiff may be excepted from the requirement of using expert testimony to prove causation.”  Id. (citation and quotation marks omitted).  See Hoopiiaina v. Intermountain Health Care, 740 P.2d 270, 271-72 (Utah App. 1987) (“In the absence of an expert to testify for plaintiff that the [drug] harmed him, . . . the jury would have no evidence upon which to base a finding that the [the drug] caused any harm to plaintiff.”); Pace v. Swerdlow, 519 F.3d 1067, 1073 (10th Cir. 2008) (“Because of the complex issues involved in a determination of proximate cause . . . Plaintiffs had to provide expert testimony.”) (citation and quotation marks omitted) (applying Utah law).

The same principles apply in Utah product liability and toxic tort cases.  “This court has held that medical expert testimony is required to prove proximate cause in a medical injury case.”  Fitz v. Synthes (USA), 990 P.2d 391, 393 (Utah 1999) (citation omitted).  In Fitz:

[Plaintiff] did not present any evidence supporting his medical causation claim, and the trial court would not allow his medical engineering expert to give an opinion on medical causation. . . .  In light of the foregoing, we conclude that . . . [plaintiff] failed to present evidence of medical causation.

Id. at 394.  In Reeves v. Geigy Pharmaceutical, Inc., “[t]he factual element underlying all [plaintiff’s] pleaded theories of liability is that his severe skin injuries were caused by [certain] drugs.”  764 P.2d 636, 640 (Utah App. 1988).  “Because these matters are outside the knowledge and experience of laypeople, expert medical testimony was required to establish causation, the standard of care, and its breach.”  Id.

Likewise, in warning cases, expert testimony is necessary because “[a] lay jury is not able to call on ‘their own life experiences’ to determine the adequacy of a drug label.”  Christison v. Biogen Idec, Inc., 199 F. Supp.3d 1315, 1340 (D. Utah 2016).  See King v. Searle Pharmaceuticals, Inc., 832 P.2d 858, 864 (Utah 1992) (“it cannot be concluded that an inference of [defendant’s] liability can be deduced from common experience and knowledge.  Accordingly, res ipsa loquitur is not sufficient to create a factual issue as to causation.”); Smith v. Terumo Cardiovascular Systems Corp., 2017 WL 2985749, at *4 (D. Utah July 12, 2017) (medical device case; “[m]edical causation (both but-for and proximate) must come from expert testimony (footnote omitted); Shipley v. Forest Laboratories, Inc., 2015 WL 4199739, at *4 (D. Utah July 13, 2015) (“In prescription drug cases, the causation element requires proof, usually in the form of expert testimony, of both general and specific causation.”) (citation omitted); Boucher v. Zimmer, Inc., 2010 WL 3815706, at *3 (D. Utah Sept. 27, 2010) (“because any testimony on the design of the [medical device] will present technically complex issues that are outside of the realm of jurors’ ordinary experience, Plaintiffs must offer admissible expert testimony in order to establish a design defect”); Coburn v. Smithkline Beecham Corp., 174 F. Supp.2d 1235, 1239 (D. Utah 2001) (“unclear . . . how Plaintiffs will establish that [a drug] was a cause of [plaintiff’s injuries] without eliciting expert testimony concerning general causation”).

Vermont

Under Vermont law, “expert testimony is ordinarily required to prove medical causation.”  Sweet v. St. Pierre, 201 A.3d 978, 987-88 (Vt. 2018) (citation omitted).  “When the facts to be proved are such that any layman of average intelligence would know from his own knowledge and experience that the accident was the cause of the injury, no expert testimony is needed to establish the causal connection; however, where the causal connection is obscure, expert testimony is required.”  Egbert v. Book Press, 477 A.2d 968, 969 (Vt. 1984).  Where failure of an implanted medical device was at issue, “fault and causation are sufficiently complex as to be beyond the scope of common knowledge to a layperson”, so “that expert testimony was required to prove that theory.”  Taylor v. Fletcher Allen Health Care, 60 A.3d 646, 649-50 (Vt. 2012).  “While it is possible that the failure of the apparatus was a direct and proximate result of plaintiff’s fall, there is no way for a jury to intelligently evaluate the evidence without expert testimony.”  Id. at 651.

The same considerations apply to Vermont product liability and toxic tort litigation.  In Blanchard v. Goodyear Tire & Rubber, 30 A.3d at 1271 (Vt. 2011), a toxic tort case, summary judgment was appropriate where “[n]othing in [plaintiff’s expert’s] testimony was sufficient to support a jury finding of specific causation.”  Id. at 1278.  Thus, another Vermont court held:

[P]laintiffs in toxic exposure cases must demonstrate specific causation by submitting evidence concerning the amount, duration, intensity, and frequency of exposure.  In the absence of expert testimony, [plaintiffs] cannot establish these essential elements of their claims.

Dakers v. Bartow, 2018 WL 8415310, at *7 (D. Vt. Sept. 10, 2018) (Blanchard citation omitted).  In a drug case:

Plaintiffs must meet their burden of proving that ingestion of [the drug] caused the [injuries] in this case by offering expert testimony.  That expert testimony has been ruled inadmissible under Daubert.  Without expert testimony . . ., it is not possible to show that any inadequacy in warning about [the drug] was a substantial factor in bringing about the [those injuries].

Blanchard v. Eli Lilly & Co., 207 F. Supp.2d 308, 322 (D. Vt. 2002), see id. at 314 (“expert testimony is required to establish causation in this case”) (citations omitted).

Virginia

“[E]xpert testimony is required” in Virginia to address any “complicated medical question that is not within the understanding of a lay person.”  Summers v. Syptak, 801 S.E.2d 422, 426 (2017).

Inasmuch as the causes of the injuries . . . are determinable only in the light of scientific knowledge, it has been recognized that expert testimony is usually necessary to support the conclusion as to causation.  The only exception to this requirement of expert testimony is the unusual case where the negligence and harmful results are sufficiently obvious as to lie within common knowledge.

Fitzgerald v. Manning, 679 F.2d 341, 350 (4th Cir. 1982) (citations and quotation marks omitted) (applying Virginia law).  See Williams v. Lowe’s Home Centers, Inc., 2018 WL 4699501, at *2 (Va. App. Oct. 2, 2018) (“when medical issues are complex, as in this case, causation must be determined by a medical expert”); Precision Pipeline, LLC v. Dominion Transmission, Inc., 2018 WL 3744018, at *3 (E.D. Va. Aug. 7, 2018) (“Without any expert testimony on the subject, [cross-plaintiff] cannot ask a lay jury to determine the complicated issue of causation.”); Clark v. Cobb, 2006 WL 6198463, at *4 (E.D. Va. Oct. 20, 2006) (“Plaintiff cannot establish the element of causation, an essential element of his negligence claim, without expert testimony”).

Virginia enforces the same requirements in toxic tort and product liability litigation.  “To prove causation in a toxic tort action, a plaintiff must offer relevant and reliable expert testimony, as the health effects of toxic exposure to chemicals are beyond the knowledge and experience of the average layperson.”  Zellers v. NexTech Northeast, LLC, 533 F. Appx. 192, 200 (4th Cir. 2013) (applying Virginia law).  Zellers affirmed the district court’s holding:

[I]n toxic tort cases, relevant and reliable expert testimony is required to prove (1) “that a particular chemical is harmful to humans generally,” i.e., general causation, and (2) “that exposure to the potentially harmful agent actually caused [the plaintiff’s injury],” i.e., specific causation.

Zellars v. NexTech Northeast, LLC, 895 F. Supp.2d 734, 739 (E.D. Va. 2012).

“Expert testimony is generally necessary to prove proximate causation in a products liability case.”  Schmitt-Doss v. American Regent, Inc., 2014 WL 3853184, at *8 (W.D. Va. Aug. 5, 2014), aff’d, 599 F. Appx. 71 (4th Cir. 2015) (for reasons stated by district court).  “[I]n a products liability action, proof of causation must ordinarily be supported by expert testimony because of the complexity of the causation facts.”  Kennedy v. Joy Technologies, Inc., 455 F. Supp.2d 522, 525 (W.D. Va. 2006), aff’d in pertinent part, 269 F. Appx. 302 (4th Cir. 2008) (applying Virginia law).  See Sanyal v. Toyota Motor North America, Inc., 2015 WL 3650725, at *7 (E.D. Va. June 11, 2015) (identical language); Cavallo v. Star Enterprise, 892 F. Supp. 756, 774 (E.D. Va. 1995) (“expert testimony is required to prove that exposure to a toxic substance caused a certain injury or illness”) (footnote omitted), aff’d in pertinent part, 100 F.3d 1150 (4th Cir. 1996).

For that proposition, both Kennedy and Sanyal quoted a prescription drug case, McCauley v. Purdue Pharma L.P., 331 F. Supp.2d 449, 464 (W.D. Va. 2004), demonstrating that expert testimony is required in prescription medical product liability litigation.  See Ball v. Takeda Pharmaceuticals America, Inc., 963 F. Supp.2d 497, 508, 510 (E.D. Va. 2013) (“plaintiff faces a fatal problem: she has no expert witness”; “[s]he must have expert testimony to meet her burden of proof”); Boysaw v. Purdue Pharma, 2008 WL 4452650, at *4 (W.D. Va. Sept. 30, 2008) (also quoting McCauley), aff’d, 320 F. Appx. 178 (4th Cir. 2009) (for reasons stated by district court); Evans v. Mentor Corp., 2005 WL 1667661, at *1 (E.D. Va. June 28, 2005) (also quoting McCauley); Hartwell v. Danek Medical, Inc., 47 F. Supp.2d 703, 707 (W.D. Va. 1999) (“[p]roof of legal causation in a medical device case must be by expert testimony”).

Virgin Islands

Virgin Islands law also follows “the general requirement of expert testimony on causation in a complex, toxic tort case.”  Henry v. St. Croix Alumina, LLC, 572 F. Appx. 114, 120 (3d Cir. 2014) (applying Virgin Islands law).  “[A] plaintiff is required to supply expert testimony in order to survive summary judgment on a design defect claim.”  Anders v. Puerto Rican Cars, Inc., 409 F. Appx. 539, 542-43 (3d Cir. 2011) (applying Virgin Islands law).  As the District Court explained in Anders:

[P]roving the existence of a defect in a product requires testimony from a qualified expert.  Where the issue concerns a product’s design, it would seem that expert opinion is the only available method to establish defectiveness, at least where the design is not patently defective.  Proving that an alleged defect was the legal cause of an injury requires testimony from a qualified expert who can testify about specific causation. . . .  Expert testimony offered by a competent expert who has an analytical and factual basis for his opinions should be required of plaintiffs in an automotive products liability case.

Anders v. Puerto Rican Cars, Inc., 2009 WL 3007367, at *9 (D.V.I. Sept. 15, 2009) (citations and quotation marks omitted), aff’d, 409 F. Appx. 539 (3d Cir. 2011).  See Washington v. HOVENSA, LLC, 2011 WL 6965855, at *1 (D.V.I. Dec. 13, 2011) (“[E]xpert testimony is required to prove causation in cases where the complexities of the human body place questions as to the cause of pain or injury beyond the knowledge of the average layperson.”) (internal quotations omitted).

Virgin Islands law follows the same principles in prescription medical product liability litigation:

Plaintiff’s case requires expert testimony to satisfy her burden with respect to both general causation and specific causation. In this case, “general causation” addresses the question of whether the ingredients of [drug] products are capable of causing [the relevant injury] in humans at therapeutic dose levels, while “specific causation” addresses whether those ingredients actually did cause [plaintiff’s injury].  If plaintiff’s expert opinion evidence regarding causation is inadmissible or insufficient to sustain a jury verdict in her favor, summary judgment is required to be granted to defendant.

Wade-Greaux v. Whitehall Laboratories, Inc., 874 F. Supp. 1441, 1475 (D.V.I. 1994) (citations omitted), aff’d mem, 46 F.3d 1120 (3d Cir. 1994).

Washington

Washington law holds that, when “[m]ust a patient present an expert medical opinion,” is a question “of law.”  Bauer v. White, 976 P.2d 664, 666 (Wash. App. 1999).

In general, expert testimony is required when an essential element in the case is best established by an opinion which is beyond the expertise of a layperson.  Expert testimony will generally be necessary to establish . . . most elements of causation. . . .  Medical facts must be proved by expert testimony unless they are observable by laypersons and describable without medical training.

Berger v. Sonneland, 26 P.3d 257, 267 (Wash. 2001) (footnotes omitted).  “Where the injury involves obscure medical factors which are beyond an ordinary lay person’s knowledge, necessitating speculation in making a finding, there must be expert testimony that the negligent act probably caused the injury.”  Riggins v. Bechtel Power Corp., 722 P.2d 819, 824 (Wash. App. 1986).  See Nikolayev v. Oyler, 143 Wash. App. 1012, 2008 WL 458649, at *2 (Wash. App. Feb. 21, 2008) (“The plaintiff must prove the causal relationship between the accident and his injuries.  And that requires expert testimony.”) (citation omitted); Cox v. Keg Restaurants U.S., Inc., 935 P.2d 1377, 1380 (Wash. App. 1997) (“Submitting the issue to the jury without such [expert] testimony is improper because the jury is thus invited to reach a result based on speculation and conjecture.”); Schudel v. General Electric Co., 35 F. Appx. 481, 484 (9th Cir. 2002). (“Because [plaintiff’s] injuries involved obscure medical factors and laypeople could not determine the injuries’ cause without resorting to speculation or conjecture, expert testimony was required to establish causation.”) (citation omitted) (applying Washington law); Bradley v. Wal-Mart Stores, Inc., 544 F. Supp.2d 1167, 1171 (W.D. Wash. 2008) (“A plaintiff must present medical testimony to establish the causal link between the injury and the incident.”).

The same is true in product liability.  “Expert testimony is required to establish causation when an injury involves obscure medical factors that would require an ordinary lay person to speculate or conjecture in making a finding.”  Bruns v. PACCAR, Inc., 890 P.2d 469, 477 (Wash. App. 1995).  See Koehler v. Allstate Insurance Co., 163 Wash. App. 1002, 2011 WL 3433304, at *7 (Wash. App. 2011) (“In the absence of any expert testimony supporting [plaintiff’s] allegations against [the product], the trial court properly granted summary judgment.”); McPhee v. Ford Motor Co., 135 Wash. App. 1017, 2006 WL 2988891, at *4 (Wash. App. Oct. 16, 2006) (summary judgment affirmed where plaintiff failed “to produce an affidavit from a qualified expert witness alleging specific facts that support a medical causation opinion”); Newkirk v. ConAgra Foods, Inc., 727 F. Supp.2d 1006, 1034 (E.D. Wash. 2010) (“in light of the exclusion of Plaintiffs’ [expert] evidence, Plaintiffs have failed to provide sufficient admissible evidence to support their burden of proof on any of their claims”), aff’d, 438 F. Appx. 607, 609 (9th Cir. 2011) (“Without the proffered expert testimony, [plaintiff] cannot show that [defendants] caused his disease.”); Henricksen v. ConocoPhillips Co., 605 F. Supp.2d 1142, 1177 (E.D. Wash. 2009) (“General causation and specific causation are essential elements of Plaintiffs’ prima facie case for each claim asserted in this litigation.  Expert testimony is necessary to make this showing since this is a toxic tort lawsuit.”) (citation omitted); Whisnant v. United States, 2006 WL 8442606, at *2 (W.D. Wash. Oct. 24, 2006) (“Fatal to plaintiffs’ case is the lack of expert testimony demonstrating the contaminants involved are capable of causing the specific ailments from which [she] suffers.”).

In cases involving use of prescription medical products, a plaintiff “ha[s] the burden of presenting expert medical testimony to demonstrate a causal link between the drug dose and the harmful effect.”  Smith v. Multicare Health System, 162 Wash. App. 1024, 2011 WL 2437797, at *2 (Wash. App. June 20, 2011).

[Plaintiff] must employ expert testimony if establishing this element would involve obscure medical facts requiring a lay person to speculate. . . .  [S]he must therefore present expert testimony assisting the jury in determining [the drug’s] impact on her and isolating it as a cause of her [injury]. . . .  Without this expert testimony, she cannot support a prima facie product liability action.

Sams v. Johnson & Johnson, 2015 WL 8213228, at *2 (W.D. Wash. Dec. 8, 2015) (citations omitted).

West Virginia

In West Virginia, “in a product liability case, the expert witness is ordinarily the critical witness.”  Morningstar v. Black & Decker Manufacturing Co., 253 S.E.2d 666, 682 (W.Va. 1979).  West Virginia law requires resort to expert testimony “where the injury is obscure, that is, the effects of which are not readily ascertainable, demonstrable or subject of common knowledge.”  Strahin v. Cleavenger, 603 S.E.2d 197, 211 (W. Va. 2004).

[W]here the exact nature and probable genesis of a particular type of injury involves complicated medical questions far removed from the ordinary experience and knowledge of laymen, only an expert can give competent opinion evidence as to the cause of the injury.

Turner v. Speedway LLC, 2015 WL 4392398, at *8 (S.D.W. Va. July 15, 2015) (citation and quotation marks omitted).

West Virginia “precedent reflects that expert testimony will be necessary to sustain an evidentiary burden when the matters involved are beyond the common knowledge and experience of the average juror.”  J.C. v. Pfizer, Inc., 814 S.E.2d 234, 243 (W. Va. 2018).  J.C., a prescription medical product liability case, held that expert testimony was critical to any evaluation of FDA-approved drug labeling.

[E]xpert testimony is necessary to sustain the burden of proof in complex cases involving matters of science, medicine, engineering, technology and the like. . . .  When the issues are beyond the common knowledge and experience of the average juror, expert testimony shall be required. . . .

[P]rescription drugs are likely to be complex medicines, esoteric in formula and varied in effect.  The terms and applications of a warning on such a drug, in order to have meaning, must be explained to the jury.  This is a subject so distinctively related to some science, profession, business or occupation as to be beyond the ken of the average layman.

*          *          *          *

The development of the [drug’s] label required the rendering of medical judgments as to whether essential information concerning risk is sufficiently conveyed; regulatory considerations; and how language in the label might be interpreted by physicians based upon how health services are provided in a given country.  Accordingly, . . . the subject matter . . . [is] not within the common knowledge and experience of the average juror and . . . [requires] expert testimony on the adequacy of the [drug’s] label.”  To find otherwise . . . would be to invite an unsound, unintelligent, and speculative verdict based upon matters beyond the cognition and experience of the average juror.

Id. at 246-47 (many citations and quotation marks omitted).

Thus, “when a claim involves highly complex matters of science, medicine, engineering, technology and the like, which are beyond the common knowledge and experience of the average juror, expert testimony will be necessary.”  Id. at 249.  See Watson v. Inco Alloys International, Inc., 545 S.E.2d 294, 303 (W. Va. 2001) (“questions involving the design of and appropriate warnings for [the product] are not within the common knowledge and experience of a lay juror” and require expert testimony); Addair v. Island Creek Coal Co., 2013 WL 1687833, at *3 (W. Va. April 17, 2013) (“complex illnesses that allegedly have arisen from exposure to chemicals of which the average person has no knowledge or experience” require expert testimony); Crawford v. General Motors Corp., 2007 WL 1960611, at *3 (N.D.W. Va. July 2, 2007) (“expert testimony is required in this case because the issue of whether [the product] was defectively designed or manufactured is well beyond the understanding of the average layman”).

Other West Virginia prescription medical product cases requiring expert testimony are:  Rohrbough v. Wyeth Laboratories, Inc., 916 F.2d 970, 972 (4th Cir. 1990) (“An essential element of plaintiffs’ cause of action is proof that defendant’s vaccine caused plaintiffs’ injuries, and proof of causation must be by expert testimony.”) (applying West Virginia law); Muzichuck v. Forest Laboratories, Inc., 2015 WL 235226, at *11 (N.D. W.Va. Jan. 16, 2015) (summary judgment granted where plaintiff “submitted no expert testimony supporting her proposed alternative means of warning”); Meade v. Parsley, 2010 WL 4909435, at *7 (S.D. W. Va. Nov. 24, 2010) (summary judgment granted enforcing “the general principle that causation evidence in toxic tort cases must be in the form of expert scientific testimony”).

Wisconsin

Under Wisconsin law, “[e]xpert testimony is required to prove causation if the matter does not fall within the realm of ordinary experience and lay comprehension.”  Menick v. City of Menasha, 547 N.W.2d 778, 782 (Wis. 1996).  “Expert testimony is often required when unusually complex or esoteric issues are before the jury because it serves to assist the trier of fact.”  Pinter v. Village of Stetsonville, 929 N.W.2d 547, 558 (Wis. 2019) (citation and quotation marks omitted).  “The lack of expert testimony in cases which are so complex or technical that a jury would be speculating without the assistance of expert testimony constitutes an insufficiency of proof.”  Weiss v. United Fire & Casualty Co., 541 N.W.2d 753, 758 (Wis. 1995).

[T]he lack of expert testimony on the question of causation results in an insufficiency of proof where the issue involves technical, scientific or medical matters which are beyond the common knowledge or experience of jurors and the jury could only speculate as to what inference to draw.

Ollman v. Wisconsin Health Care Liability Insurance Plan, 505 N.W.2d 399 (Wis. App. 1993).

These principles apply in Wisconsin product liability and toxic tort litigation.  “[U]nder Wisconsin law, for Plaintiff to support his claims that chemical exposure caused him permanent injury, he must educe supporting qualified expert testimony.”  Kolesar v. United Agri Products, Inc., 412 F. Supp.2d 686, 696 (W.D. Mich. 2006) (applying Wisconsin law), aff’d, 246 F. Appx. 977, 981 (6th Cir. 2007).  A causation “conclusion without any support is not one based on expert knowledge and is not entitled to the dignity of evidence.  It has no scientific basis whatsoever.”  Smith v. Sofamor S.N.C., 21 F. Supp.2d 918, 921 (W.D. Wis. 1998).

Surgical . . . techniques and the adequacy of warnings from implant manufacturers are specialized medical issues and not within the realm of the ordinary experience of mankind”; expert testimony is required to support a defective-warning claim premised on this theory.

In re Zimmer, NexGen Knee Implant Products Liability Litigation, 884 F.3d 746, 753 (7th Cir. 2018) (citation omitted) (applying Wisconsin law).  See Jandrt v. Jerome Foods, Inc., 597 N.W.2d 744, 761 (Wis. 1999) (toxic tort plaintiff’s counsel properly sanctioned for “the absence of any scientific support for the underlying theory of causation . . . [o]nly an expert could have provided the critical link”); Johnson v. Mylan, Inc., 107 F. Supp.3d 967, 976 (E.D. Wis. 2015) (“The plaintiffs have no expert witness who can testify that [the device] was defective, or that it malfunctioned.  Pharmacology, toxicity, and . . . drug delivery are not matters within common knowledge or ordinary experience.”); Schultz v. Glidden Co., 2012 WL 968005, at *2 (E.D. Wis. March 21, 2012) (“To avoid summary judgment in a toxic tort case, the plaintiff must produce admissible expert testimony on the issue of both general and specific causation.”) (citation omitted), rev’d on other grounds, 721 F.3d 426 (7th Cir. 2013); Lemmermann v. Blue Cross Blue Shield, 713 F. Supp.2d 791, 813 (E.D. Wis. 2010) (“plaintiff has no evidence to support critical elements of her duty to warn or strict liability claims.  The expert testimony proffered by the plaintiff screams of unreliability”); Menges v. Depuy Motech, Inc., 61 F. Supp.2d 817, 824 (N.D. Ind. 1999) (“[p]roof of legal causation in a medical device case must be by expert testimony”) (applying Wisconsin law); Valente v. Sofamor, S.N.C., 48 F. Supp.2d 862, 877 (E.D. Wis. 1999) (summary judgment granted because “the plaintiffs fail to offer admissible expert testimony to show that the [medical] device designed, manufactured, promoted, distributed, and sold by the defendants caused the plaintiffs to sustain injuries”); Cali v. Danek Medical, Inc., 24 F. Supp.2d 941, 950 (W.D. Wis. 1998) (summary judgment granted after plaintiff’s experts excluded; “this is a case which requires medical testimony to establish causation between the device and plaintiff’s injury.”); Ruhland v. Walter Kidde Portable Equipment, Inc., 179 F.R.D. 246, 251 (W.D. Wis. 1998) (summary judgment granted; “this product liability action is sufficiently complex as to require expert testimony”).

Wyoming

Wyoming precedent requires expert testimony “[i]f the origin of the injury is obscure and not readily apparent to a layman, or if there are several equally probable causes of the condition.”  Sayer v. Williams, 962 P.2d 165, 168 (Wyo. 1998).  Thus, “expert testimony is required to establish causation unless the injury is immediately and directly or naturally and probably the result of an accident.”  Bodily v. State, 320 P.3d 240, 250 (Wyo. 2014).  See Harris v. Grizzle, 625 P.2d 747, 752 (Wyo. 1981) (“The rule . . . requiring expert testimony is applicable to the case at hand” involving use of a medical device).  In a product liability action, the Wyoming Supreme Court held:

[Plaintiff’s] case rested entirely on unsupported speculation by [an expert].  [Plaintiff] presented no admissible evidence which would indicate that the [product] was not reasonably safe when designed and manufactured; and, therefore, the court properly granted summary judgment

Campbell v. Studer, Inc., 970 P.2d 389, 394 (Wyo. 1998).

Similarly, Wyoming product liability actions involving prescription medical products require expert testimony.

[P]ersonal injury cases involving pharmaceuticals, toxins or medical devices involve complex questions of medical causation beyond the understanding of a layperson.  Complex causal relationships require expert testimony.  Accordingly, [plaintiff] must put forward expert testimony to survive summary judgment and dismissal of his case.

Ronwin v. Bayer Corp., 2008 WL 11427934, at *2 (D. Wyo. Oct. 1, 2008).  Plaintiff lacked admissible expert testimony, and summary judgment was entered.  Id. at *4 (“Without expert reports and testimony to establish a causal link between his seven month [drug] ingestion and his alleged physical injuries, [plaintiff] has failed to establish the existence of a genuine issue of material fact.”).  Summary judgment was affirmed on appeal.  Prescription medical product cases “involve[] complicated causation issues, [such that] all plaintiffs were required to present expert testimony to prove injury and a causal connection.”  Ronwin v. Bayer Corp., 332 F. Appx. 508, 514 (10th Cir. 2009) (“absent expert testimony on causation, summary judgment was appropriate”) (applying Wyoming law).