Subject: Daubert

Can a Treating Physician’s Medical Testimony Be “Lay Opinion”? Divided Sixth Circuit Panel Disagrees on Where to Draw the Line

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Federal Rules of Evidence 701 and 702 govern the admissibility of lay and expert opinion testimony, respectively, in federal courts. Rule 701(c) helps paint the line between the two, providing that an opinion “based on scientific, technical, or other specialized knowledge within the scope of Rule 702” cannot be admitted as a lay opinion. This requirement was added in the 2000 Amendments to Rule 701 to address what the Advisory Committee described as a risk “that the reliability requirements set forth in Rule 702 will be evaded through the simple expedient of proffering an expert in lay witness clothing.” Given this history, one might expect courts to err toward applying Rule 702 to any testimony that inherently draws on expertise that laypeople do not possess. But, as illustrated by the Sixth Circuit’s split decision in United States v. Betro, — F.4th —, 2024 WL 3811838 (6th Cir. 2024), some courts use a different approach.

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Plaintiffs’ Second Bite at the General Causation Apple Fares No Better Than the First in Acetaminophen MDL

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In December 2023, back when the ink was still drying on the amendments to Federal Rule of Evidence 702, the Southern District of New York excluded all five general causation experts proffered by plaintiffs in the In re Acetaminophen MDL whose cases had been selected for trial.  We discussed that impressively detailed and painstaking decision here. Observing that all 50 states require proof of general causation in product liability cases and that the plaintiffs now had no experts to carry that water, the court instituted an order to show cause process that led to the dismissal of approximately 550 cases. However, over the defendants’ objections, the court permitted a small handful of new arrivals to the MDL to name their own general causation expert and try again. In yet another impressively meticulous opinion, the court recently doubled down on its Rule 702 “gatekeeping” role and excluded the new plaintiffs’ backup general causation expert in In re Acetaminophen – ASD-ADHD Prod. Liab. Litig., No. 22MC3043 (DLC), 2024 WL 3357608 (S.D.N.Y. July 10, 2024).

The plaintiffs in In re Acetaminophen allege that prenatal use of acetaminophen caused attention deficit hyperactivity disorder (ADHD) and/or autism spectrum disorder (ASD) in offspring. The plaintiffs’ first five proffered general causation experts were excluded in part because the court took issue with the experts’ “transdiagnostic” approach — combining literature of ADHD and ASD into a single analysis — because it merely “obscured limitations in the scientific literature.”   The new plaintiffs’ expert — number six overall — sidestepped the “transdiagnostic” issues and sought to opine solely on a supposed link between prenatal acetaminophen use and ADHD.  But the court, still mindful of acetaminophen’s critical role as the only pain reliever and fever reducer indicated for use during pregnancy and the FDA’s multiple reviews of its safety, remained vigilant in its Rule 702 obligation.

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California Supreme Court Walks Middle Ground on Warnings Causation but Reaffirms Learned Intermediary Doctrine in Himes

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As we reported in April, the United States Court of Appeals for the Ninth Circuit certified a question on California’s Learned Intermediary Doctrine in Himes v. Somatics, LLC, 2022 WL 989469 (9th Cir. Apr. 1, 2022). The California Supreme Court has now decided the issue in a way that walks the middle ground. On the one hand, the court rejected plaintiff’s call for recognizing an exception to the learned intermediary rule and reaffirmed the basic rule that a manufacturer’s duty to warn runs to the prescribing physician. On the other hand, the court ultimately lowered plaintiff’s burden of providing warnings causation. The opinion has clear ramifications not only on dispositive motion and trial practice, but on discovery strategies in prescription drug and medical device cases.

The question before the court was whether a plaintiff is “required to show that a stronger risk warning would have altered the physician’s decision to prescribe the product,” or whether a plaintiff may instead establish causation “by showing that the physician would have communicated the stronger risk warning[ ] to the plaintiff, either in their patient consent disclosures or otherwise, and a prudent person in the patient’s position would have declined the treatment after receiving the stronger risk warning.” (Himes v. Somatics, LLC, 16 Cal.5th 209 (2024).)

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Peer Review Can’t Save “Junk Science” from FRE 702 Judicial Gatekeeping – In re: Roundup Court Excludes Expert Whose Opinions Had Been Published in Peer-Reviewed Literature

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When tasked with assessing the admissibility of expert testimony under Federal Rule of Evidence 702, courts often cite the so-called Daubert factors as criteria that guide the inquiry.  Among those factors is “whether the [expert’s] theory or technique has been subjected to peer review and publication.”  Daubert v. Merrell Dow Pharms., Inc., 509 U.S. 579 (1993).  The Daubert Court observed that, although publication “is not a sine qua non of admissibility,” peer review “increases the likelihood that substantive flaws in methodology will be detected.”  But peer review is not coterminous with the Rule 702 inquiry that federal courts are called upon to make, especially with the rise of so-called predatory publishing and journals with relaxed (or absent) peer review processes.  As one court recently observed, “a court can’t wave junk science through the Daubert gate simply because it survived some prepublication peer-review process.”  In re: Roundup Products Liability Litigation, 2024 WL 3074376 (N.D. Cal. June 20, 2024).

In In re: Roundup, the plaintiff claimed to have developed non-Hodgkin’s lymphoma (NHL) as a result of using the defendant’s herbicide.  In support of that claim, he offered a single expert on the issue of whether glyphosate, the active ingredient in the herbicide, can cause NHL in humans.  The expert’s opinions were all contained in two peer-reviewed and published articles that the expert had co-authored.  But only one of the two—a 2019 meta-analysis of six epidemiological studies addressing the link between glyphosate and NHL, which had been published before the expert became involved in the litigation—grappled with the available epidemiological evidence.  The defendant attacked that paper on multiple grounds, and the court agreed that it constituted “junk science” with several flaws each independently justifying its exclusion.

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Northern District of Illinois Holds that Seventh Circuit Precedent is Incompatible with Rule 702 as Amended

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In explaining the December 2023 amendments to Federal Rule of Evidence 702, the Advisory Committee called out several ways in which “many courts” had “incorrectly” applied Rule 702 and failed to adequately discharge their duty as gatekeepers with regard to expert witness testimony.  The import of those comments is that existing precedent on Rule 702 may be “incorrect” and must be re-examined.

A case pending in the Northern District of Illinois serves as a fine illustration of how this re-examination should work in practice.  In West v. Home Depot U.S.A., Inc., 2024 WL 1834112 (N.D. Ill. Apr. 26, 2024), the plaintiff alleged that she was injured when portions of a store display fell on her.  She offered a trio of experts to opine that her claimed injuries had been caused by the incident, but none of them “were aware of, let alone reviewed, [her] highly salient medical history prior to issuing their causation opinions.”  Rather, they were treating physicians who based their opinions solely on their post-incident treatment of the plaintiff.

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A KIND Result After Insufficient and Biased Consumer Perception Evidence

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Consumer perception evidence is necessary for plaintiffs to survive summary judgment in a false advertising class action, but vacillating and flawed connections between the evidence and the key question of what a reasonable consumer would expect may lead to its exclusion.  The Second Circuit, in Bustamante v. KIND, LLC, 2024 WL 1917155 (2d Cir. May 2, 2024), provides an illustrative example of this, affirming the Southern District of New York’s exclusion of plaintiffs’ experts and grant of summary judgment to a snack foods manufacturer in a false advertising class action.

In Bustamante, Plaintiffs alleged they were deceived by the packaging of KIND snack bars as “All Natural” despite the inclusion of certain “non-natural” ingredients, and their lawsuit asserted warranty, unjust enrichment, negligent misrepresentation, and state consumer protection statute claims.  Although there were differing elements to Plaintiffs’ various claims, they were narrowed for the purposes of summary judgment to deception, materiality, and injury, with only the element of deception at issue on appeal.

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