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

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.