Parents of two children with birth defects sued Merrell Dow Pharmaceuticals, alleging that the anti-nausea drug Bendectin caused the defects. In support of summary judgment, Merrell Dow offered an expert affidavit concluding that published epidemiological studies did not show a causal link between Bendectin and human birth defects. The plaintiffs countered with expert opinions based on reanalyses of published epidemiological data, animal studies, chemical structure analyses, and in vitro studies that, they claimed, supported causation. The district court excluded plaintiffs' expert evidence, applying the Frye "general acceptance" standard and finding the methodologies insufficiently accepted in the relevant scientific community. With plaintiffs' evidence excluded, the court granted summary judgment to Merrell Dow. The Ninth Circuit affirmed, holding that Frye survived adoption of the Federal Rules of Evidence and governed admissibility of novel scientific evidence.
Do the Federal Rules of Evidence, particularly Rule 702, displace the Frye "general acceptance" test for scientific expert testimony, and if so, what standard governs the admissibility of such evidence?
Under Federal Rule of Evidence 702, the trial judge must act as a gatekeeper to ensure that scientific expert testimony is both reliable and relevant. Reliability requires that the testimony constitute "scientific knowledge" grounded in the methods and procedures of science, not mere subjective belief or unsupported speculation. Relevant expert testimony must "fit" the case by assisting the trier of fact to understand the evidence or determine a fact in issue. In making this preliminary determination under Rule 104(a) (by a preponderance of the evidence), courts engage in a flexible, case-specific inquiry and may consider nonexclusive factors such as: (1) whether the theory or technique can be and has been tested; (2) whether it has been subjected to peer review and publication; (3) the known or potential rate of error and the existence and maintenance of standards; and (4) general acceptance within the relevant scientific community. The Frye test of general acceptance is not a necessary or sufficient condition for admissibility under the Federal Rules.
The Federal Rules of Evidence supersede Frye's "general acceptance" test. Rule 702 imposes a flexible, reliability-and-relevance gatekeeping role on trial judges for scientific expert testimony. The Ninth Circuit's application of Frye was error; the judgment was vacated and the case remanded for further proceedings under the proper standard.
The Court began with the text and structure of the Federal Rules of Evidence. Rule 402 reflects a liberal policy of admissibility for relevant evidence, while Rule 702 requires that expert evidence rest on "scientific knowledge" and aid the trier of fact. "Scientific knowledge," the Court explained, connotes a grounding in the scientific method—i.e., methods and procedures characterized by testing, falsifiability, and empirical validation. The inquiry is not about the expert's credentials alone or the persuasiveness of the conclusion, but about the validity and reliability of the underlying principles and methodology and their proper application to the case. Rejecting the Frye test as atextual and incompatible with the Federal Rules' framework, the Court held that general acceptance is a relevant, but not dispositive, consideration. It outlined a flexible set of factors to guide reliability determinations: testability; peer review and publication; known or potential error rates and standards controlling the technique's operation; and general acceptance. The Court also emphasized "fit": even reliable science must be sufficiently tied to the facts at issue to be helpful under Rules 401 and 702. The judge must make these preliminary determinations under Rule 104(a). At the same time, the Court cautioned that the admissibility threshold is not certainty. "Shaky but admissible" evidence should be tested through the adversary process—vigorous cross-examination, presentation of contrary evidence, and careful instruction on the burden of proof—rather than by wholesale exclusion. Because the Ninth Circuit relied on Frye, the Supreme Court vacated and remanded for application of the correct Rule 702 standard. The Court did not decide whether the particular expert opinions offered by the plaintiffs were admissible on the merits.
Daubert is the cornerstone of modern expert evidence law. It replaced Frye's rigid general-acceptance test with a flexible, judge-centered reliability and relevance inquiry under Rule 702. The decision established that trial judges must screen expert testimony for methodological soundness and fit, leading to pretrial Daubert motions and hearings that can be outcome-determinative, especially in scientific causation cases. Daubert also launched the "Daubert trilogy": General Electric Co. v. Joiner (1997) (abuse-of-discretion appellate review and scrutiny of analytical gaps) and Kumho Tire Co. v. Carmichael (1999) (extending Daubert's gatekeeping to all expert testimony, not just "scientific"). Subsequent amendments to Rule 702 (notably in 2000 and 2023) codify and clarify the gatekeeping role and the proponent's burden. Many states have adopted Daubert or variants; others retain Frye. For law students, Daubert is essential for understanding the interplay between evidence law, scientific methodology, and civil procedure strategy.
Daubert reoriented expert evidence law around the Federal Rules of Evidence, assigning trial judges a gatekeeping role to ensure that expert opinions are grounded in reliable methodology and genuinely assist the factfinder. Its flexible, factor-based analysis replaced Frye's rigid general-acceptance rule and reshaped litigation strategy through pretrial admissibility challenges.