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Not too long ago we researched precedent that forbade persons claiming to be “FDA experts” from opining that products are “adulterated” or “misbranded.”  In that post, we mentioned that this research is a subset of a “general” precedent “precluding expert opinions on questions of law,” which we didn’t get into because Bexis’ book addressed it.  But since we recently ran across an unusually favorable new case on this subject, we thought we’d address it again.  It’s not a tort case – it’s not even a civil case – so it demonstrates how widespread the problem legalistic “expert” witnesses extends, and also how wide-ranging relevant caselaw can be.

The defendant in United States v. Xue, 2022 WL 1027634 (E.D. Pa. April 6, 2022), was being prosecuted for “conspiracy to steal trade secrets.”  It doesn’t matter what the secrets were or who was involved.  The prosecution offered up perfectly well-qualified expert witnesses who proposed to testify about a variety of things, but the one that matters for present purposes is that they intended to characterize the material at issue as “trade secrets.”  The defendant opposed admission of that testimony on the ground that “trade secret” – like “adulterated”/”misbranded” in our prior post – was a legal term of art, and thus improper as a basis for an expert opinion.  Id. at *9.

The court agreed with the defendant, and wrote an unusually thorough explanation of why this testimony was being excluded.  “One of the ‘ultimate issues’ in this case [was] whether the alleged misappropriated information falls within the statutory definition of ‘trade secret.’”  Id. at *9-10 (citing 18 U.S.C. §1839 (3)(A-B), which defines “trade secret”).  While F.R. Evid. 704(a) allows an expert witness to opine on an “ultimate issue,” nothing in the Federal Rules allows experts to opine on the law.  Id.  Rather, “‘an expert witness is prohibited from rendering a legal opinion.’”  Id. (quoting Berckeley Investment Group, Ltd. v. Colkitt, 455 F.3d 195, 217 (3d Cir. 2006)).

Thus, “courts commonly exclude ‘legal terms of art’ from expert testimony.”  Id. at *10 (citation omitted).  In the Third Circuit, Flickinger v. Toys R Us-Delaware, Inc., 492 F. Appx. 217 (3d Cir. 2012), prohibited an expert from opining on what constituted “exclusive control,” “dangerous condition,” “substantial cause,” and “negligence.”  Id. at 224.  Numerous district courts in the Third Circuit have reached similar results.  E.g., Dalgic v. Misericordia University, 2019 WL 2867236, at *13 (M.D. Pa. July 3, 2019) (expert may not opine about “proximate cause”); Perez v. Townsend Engineering Co., 562 F. Supp.2d 647, 652 (M.D. Pa. 2007) (precluding expert witness from testifying that a product was “defective,” “unreasonably dangerous,” or was the “proximate cause” of injury); Gallatin Fuels, Inc. v. Westchester Fire Insurance Co., 410 F. Supp.2d 417, 422 (W.D. Pa. 2006) (expert could not opine that an insurer acted in “bad faith”); McCrink v. Peoples Benefit Life Insurance Co., 2005 WL 730688, at *4 (E.D. Pa. March 29, 2005) (same).  See Xue, 2022 WL 1027634, at *11.

Turning to other circuits, Xue began, id., with Bexis’ favorite precedent for precluding expert testimony on conclusions of law:  Burkhart v. Washington Metropolitan Area Transit Authority, 112 F.3d 1207, 1212 (D.C. Cir. 1997), which determined that the term “as effective” was not subject to an expert opinion because it was a legal “term of art with a meaning ‘separate’ and ‘distinct’ from the vernacular.”  Id. at 1213.

[The expert’s] testimony as to the applicable legal standard was plainly erroneous, thus demonstrating the danger in allowing experts to testify as to their understanding of the law.  Each courtroom comes equipped with a “legal expert,” called a judge, and it is his or her province alone to instruct the jury on the relevant legal standards.

Id. (citations omitted).  Other appellate decisions cited in Xue are:  United States v. Barile, 286 F.3d 749, 759 (4th Cir. 2002) (prohibiting expert testimony on FDCA term “materially misleading”); Torres v. County of Oakland, 758 F.2d 147, 151 (6th Cir. 1985) (prohibiting expert testimony on statutory term “as effective”).

Because “the term ‘trade secret’ is a term of art with specialized legal meaning,” it was properly the subject of a jury instruction from the court, not opinions from the parties’ expert witnesses.  Xue, 2022 WL 1027634, at *12.

Ultimately, the jury must decide whether the Government has proved beyond a reasonable doubt that the documents in issue contain “trade secrets,” after carefully applying the facts they find to the law.  Thus, the expert witnesses may not testify using the term “trade secret” because doing so would usurp the District Court’s pivotal role in explaining the law to the jury.

Id. (citation and quotation marks omitted).  Therefore:

As an alternative to “trade secret” or “secret,” the witnesses may testify that the information was “confidential” or “proprietary,” about any steps taken to protect the confidentiality of the information, and about industry customs and practices.  The witnesses may also use synonyms for the words “trade” and “secret.”


Finally, when we first came across Xue, we compared the list of cases Xue cited to those cited in Bexis’ Book, §10.06, fn 1.  One reason we wrote this post is that we were surprised by the lack of overlap.  Only Burkhart and Perez appeared in both places.  To some extent, that’s because Bexis’ footnote included extensive citation to state-court cases, but it’s also due to the section needing updating (the most recent case is ten years old).  Hence, Xue was worth writing up simply because it adds more recent cases that exclude expert opinions on issues of law.