This is from the non-Dechert and non-RS side of the Blog.

We recently attended a successful Ph.D. thesis defense on the seemingly narrow issue of trap states in quantum dots.  This was held in a dark wood-paneled room in a large science building on the campus of a research institution generally known by a short acronym.  In our work world, this is the sort of place we like to see on the resumes of our experts.  A few things about that thesis defense resonate with us as we discuss a recent decision from the Delaware Supreme Court that will have significant implications in a national litigation we have written about many times before, as well as ripples for drug and device litigations where plaintiffs may be looking at Delaware as a favorable venue.  First, just because you are an expert in your field does not mean you can speak intelligently and reliably on a specific area of science.  This is not a comment on the candidate, who was knowledgeable, articulate, and enthusiastic, but on at least some of the audience.  We know some stuff in our own field and have spent quite a bit of time reading scientific and medical literature for our cases.  Still, we have been hard pressed to do more than regurgitate parts of what we heard were we required to speak about trap states with quantum dots, let alone weigh in on the correctness of any of the conclusions in the research we heard described.  When judges let in questionable expert evidence, it can be because the judge allows experts to disregard adverse authority without a good reason.  Second, appreciating the scope and scale of what is being discussed can be critical.  Quantum dots are between one-billionth of a meter and one-hundred-millionth of a meter in size.  Their behavior is measured in trillionths of seconds.  A proper understanding of research on them requires grasping the significance of those fractions.  In dealing with the admissibility of general causation opinions related to allegedly harmful substances in product liability litigation, you better understand scope and not get confused by what is being measured.  One of the recurring issues is when a plaintiff expert relies on a study that involves exposures at levels hundreds or thousands of times above the plaintiff’s, particularly if the exposure is not really to the same thing.  Third, it helps to know the standards in advance.  What is expected from a successful thesis defense or admissible expert causation evidence can vary depending on where you are, but both properly test both procedure and substance.

With that in mind, we note that we have written quite a bit over the years about how weak the plaintiffs’ general causation evidence has been in litigation over cancer allegedly caused by nitrosamines allegedly present in various forms of the drug ranitidine.  Notably, the major reason why the plaintiffs lost in the MDL is because they could not come up with admissible general causation opinions about a link between ranitidine and any kind of cancer in humans.  The outlier came from Delaware, where what might have been considered a defense-friendly venue, gave a free pass to plaintiffs’ general causation experts.  In In re Zantac (Ranitidine) Litig., — A.3d –, 2025 WL 1903760 (Del. July 10, 2025), the Delaware Supreme Court took an interlocutory appeal and reversed the order on plaintiffs’ causation experts, reestablishing that Rule 702 in Delaware state court should be applied the same as Rule 702 is supposed to be applied in federal courts.  Beyond the impact on the litigation—more on that later—we clearly have an enunciation of more rigorous standards for the admissibility than the Zantac trial court and perhaps other Delaware trial courts had been applying.  That may make Delaware a less attractive option for plaintiffs seeking to avoid federal court.  As for the actual decision and what it means for the Delaware Zantac litigation, we will explain our views without continuing to draw links to our observations from the introduction.

The basic facts of the litigation should be familiar from prior posts, including on the Delaware Superior Court’s decision last year and an Illinois appellate decision last month.  The litigation has been driven from the start by questionable data from a questionable lab and the efforts of plaintiffs to cobble together a causation case even though many studies on the direct issue have failed to find a statistically significant increased risk of any cancer with the use of ranitidine.  In the Delaware proceeding, plaintiffs offered up a slate of ten experts to try to prove general causation for ten different types of cancer.  (Recall that, in the MDL, the plaintiffs ultimately only tried to prove causation for five types of cancer, implicitly recognizing the supporting evidence was even weaker for other types.) 

The Zantac decision identified two basic errors by the court below in denying the defendants detailed challenges to the experts’ causation opinions.  First, it had adopted “a standard that favored or presumed the admission of expert testimony,” which was inconsistent with the burden being on the proponent of the expert testimony.  Id. at *1.  “A trial judge must act as the gatekeeper of expert testimony and should not dismiss challenges to the sufficiency or reliability of an expert opinion by viewing the disputes as questions for the jury to weigh.”  Id.  The rejected approach was basically why Fed. R. Evid. 702 was revised and what we have decried in judges since who have stuck to their old ways.  Second, the court had permitted plaintiffs’ experts to “base their conclusions on studies regarding the alleged disease-causing agent rather than the product at issue in the case, without establishing a reliable bridge between the product at issue and the scientific data regarding the toxic agent.”  Id.  The rejection by the MDL court of the attempt by the plaintiffs’ experts to do the same thing was a key part of the lengthy—and correct—analysis there.  There was an issue raised by the appellants that the Delaware Supreme Court did not resolve: whether the plaintiffs’ experts have to identify a threshold dose of ranitidine or nitrosamines from ranitidine that can cause each of the types of cancer.  Id. at **12 & 18.  The Superior Court had concluded there was no such requirement and the MDL had ruled that there was.  With such a requirement, the plaintiffs’ experts in Delaware would surely be unable to offer an admissible general causation opinion.  They also would not be able, in all but the rarest cases, to show that any plaintiff’s exposure to nitrosamines from ranitidine was above that threshold, which is part of why plaintiffs argue against thresholds.

The Delaware Supreme Court’s analysis of the first issue began with the review of Daubert, the 2023 amendments to Fed. R. Evid. 702, and Delaware’s historic approach with its Rules of Evidence.  Even though Delaware had not amended its Rule 702 to match the current federal version, “[n]othing in the recent amendments conflicts with our existing precedent, and the commentary accompanying those amendments offers additional guidance as trial courts confront the difficult task of evaluating the admissibility of an expert opinion.”  Id. at *10.  The requirement that the trial court had to act as a gatekeeper and decide if the plaintiffs established the admissibility of their experts’ opinions meant that the decision below, which had largely punted, could not stand. 

. . . Defendants repeatedly challenged Plaintiffs’ experts for “cherry-picking” favorable data regarding NDMA while ignoring studies focusing directly on ranitidine. Rather than addressing Defendants’ arguments and determining whether the challenged experts reliably applied appropriate methodologies, the court dismissed these objections and labeled them as questions for the jury.

Id. at *13.  The proper role for the trial judge “may present a substantial challenge, as few judges are steeped in scientific knowledge, the trial judge may receive and evaluate testimony and ask questions of the experts and the parties’ lawyers until the court feels comfortable drawing conclusions on sufficiency and reliability.”  Id.  The failure of the court below to fulfill this role “resulted in the court finding that Plaintiffs’ experts’ opinions were admissible even though their sufficiency and reliability was not established by a preponderance of the evidence.”  Id. at *14.

The second issue involved a dive into Delaware law to find the prior focus of what must be shown to cause the injury at issue.  The law squared with common sense to require the expert “focus on the product at issue and must show that exposures examined in non-product studies on which the expert relied are reliably linked to the exposures caused by the product at issue.”  Id. at *15.  Federal decisions have long made the same distinction, which squares with the oft-repeated saying that “the dose makes the poison.”  Because nine of plaintiffs’ ten experts focused on studies on exposure to NDMA from occupation or diet, rather than presumed exposure through ranitidine use, they were clearly inadmissible under the proper test absent an admissible link.  Plaintiffs’ tenth expert offered an opinion on a link, which the trial judge had doubted but characterized as a jury question.  Id. at *17.  Under the gatekeeping duty, the trial judge was required to resolve the challenges raised as to the reliability of that opinion, along with all the others. 

The disposition of the interlocutory appeal was reversal and remand “for further proceedings consistent with this decision.”  Id. at *18.  We expect the defendants will argue that the experts have been excluded already, so summary judgment is the next step (as it was in the MDL).  After all, the court noted in a number of places with plaintiffs did not carry their burden to establish admissibility and that the experts failed to justify critical issues with their opinions.  “Correctly understood, DRE 702 and its interpretive precedent required exclusion of the challenged expert opinions.”  Id. at *10.  On the other hand, plaintiffs will surely argue that the trial court should redo its analysis applying the standards articulated by the Delaware Supreme Court and with the benefit of new arguments and, if the trial court is so inclined, new experts.  In places, the appellate court was careful not to tell the Superior Court what conclusion it should reach when applying the correct standard.

We do not suggest that the Superior Court should have simply adopted the MDL court’s conclusions. The trial court correctly undertook an independent analysis of the admissibility of Plaintiffs’ experts’ opinions. But the Superior Court’s dismissal of the significant methodological flaws identified by the MDL court—flaws that also appeared in the expert reports in Delaware—on the basis that Delaware has a different standard, was error.

Id. at *12.  If there is a redo, with or without a threshold requirement, however, the Delaware Supreme Court’s clearly sent the message that the admission of opinions riddled with so many “significant methodological flaws” would get reversed on appeal.  As it should.