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The certiorari petition in Union Carbide Corp. v. Sommerville (25-919) presents an important question about application of Federal Rule of Evidence 702 (Testimony by Expert Witnesses): Is a challenge to the factual basis for an expert’s opinion always a matter of weight for a jury to decide, or must a district judge first determine that the factual basis is sufficiently reliable to warrant admission of the opinion into evidence?
ALF has filed an amicus brief urging the Supreme Court to resolve the inter-circuit split of authority on this frequently recurring question. The brief was authored for ALF by Robert E. Johnston, Aleksandra Rybicki, and Alexa D. Halkias of Hollingsworth LLP, a firm that has significant experience defending companies in ethylene oxide litigation, and since Daubert, has been at the forefront of urging expert testimony admissibility requirements to exclude junk science.
Case Background
The plaintiff, alleging that she was chronically exposed to ethylene oxide (EtO) emitted into the atmosphere from industrial facilities, filed a putative class action for medical monitoring. A West Virginia district court excluded her expert’s proposed testimony on the ground that its factual underpinnings were insufficiently reliable, and granted summary judgment to the defendant. On appeal, a divided Fourth Circuit reversed, holding that “questions regarding the factual underpinnings of the [expert witness’s] opinion affect the weight and credibility of the witness’ assessment, not its admissibility.” Sommerville v. Union Carbide Corp., 149 F.4th 408, 423 (4th Cir. 2025).
ALF's Amicus Brief
The amicus brief discusses the 2023 amendments to Rule 702, including the reasons that they were adopted. More specifically, the amendments were intended to emphasize and clarify a district judge’s expert testimony gatekeeping role to ensure that unreliable expert opinion testimony is not presented to a jury. This includes a determination by the district judge as to whether the facts and data underlying an expert’s opinion, and the application of the expert’s methodology, are sufficiently reliable to warrant admission of the expert testimony into evidence.
The Supreme Court needs to grant certiorari and hold, contrary to the Fourth Circuit’s opinion, that challenges to the reliability of expert testimony’s factual underpinnings first must be assessed by the trial judge to determine whether they support admissibility of the expert opinion. Such a ruling by the Court would provide clarity and promote uniform application of amended Rule 702.
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