Jason Daubert and Eric Schuller were born with serious birth defects. Their parents sued Merrell Dow Pharmaceuticals, alleging that the mothers’ use of Bendectin, a prescription anti-nausea drug, caused those defects. Merrell Dow removed the California state-court actions to federal court based on diversity jurisdiction.
Merrell Dow moved for summary judgment after extensive discovery. It submitted an epidemiologist’s affidavit stating that more than 30 published epidemiological studies involving over 130,000 patients found no evidence that Bendectin causes human birth defects. The plaintiffs offered eight qualified experts who relied on test-tube and animal studies, chemical-structure comparisons, and reanalyses of existing epidemiological data to conclude that Bendectin could cause birth defects.
The District Court excluded the plaintiffs’ evidence under the Frye “general acceptance” test. It reasoned that, in light of the extensive epidemiological literature, non-epidemiological evidence could not establish causation, and that the plaintiffs’ unpublished, un-peer-reviewed epidemiological reanalyses were inadmissible. With the plaintiffs left without admissible causation evidence, the court granted summary judgment for Merrell Dow. The Ninth Circuit affirmed, likewise applying Frye and treating general acceptance, publication, and peer review as controlling considerations.
Issue #1
Whether the Federal Rules of Evidence preserved Frye’s requirement that scientific evidence be generally accepted in the relevant scientific community before it may be admitted.
Holding
No. The Federal Rules of Evidence superseded Frye’s general-acceptance test as an exclusive prerequisite for admitting scientific expert testimony in federal court.
Reasoning
Rule 402 begins from a liberal premise: relevant evidence is admissible unless another constitutional, statutory, or evidentiary rule provides otherwise. Because Frye predated the Federal Rules by decades, it could survive only if it were consistent with, or incorporated into, the Rules’ text and structure.
Rule 702 specifically governs expert testimony and permits a qualified expert to testify when scientific, technical, or other specialized knowledge will assist the factfinder. Its text does not make general acceptance an absolute condition of admissibility, and neither its drafting history nor the Rules as a whole shows an intent to adopt Frye.
A rigid general-acceptance requirement conflicts with the Rules’ liberal approach to relevant evidence and their relaxation of traditional limits on opinion testimony. General acceptance may remain relevant to reliability, but it cannot operate as Frye’s exclusive threshold rule.
Issue #2
Whether Rule 702 requires federal trial judges to screen proposed scientific expert testimony for reliability as well as relevance.
Holding
Yes. Rule 702 assigns trial judges a gatekeeping duty to ensure that scientific expert testimony is both reliable and relevant to the factual issue before the jury.
Reasoning
The phrase “scientific knowledge” requires more than an expert’s subjective belief or unsupported speculation. Scientific testimony must be grounded in scientific methods and procedures and supported by appropriate validation—what the Court called “good grounds.”
Rule 702 also requires that the testimony assist the trier of fact. This is a relevance requirement often described as “fit”: the expert’s valid reasoning or methodology must bear a valid scientific connection to the particular factual question in the case.
Under Rule 104(a), the judge must make a preliminary assessment of whether the expert’s reasoning or methodology is scientifically valid and whether it can properly be applied to the facts at issue. The inquiry focuses on the principles and methods underlying the testimony, not on whether the judge agrees with the expert’s ultimate conclusion.
Issue #3
How should a trial judge assess the reliability of proposed scientific expert testimony under Rule 702?
Holding
The inquiry is flexible, not a definitive checklist, but testing, peer review and publication, known or potential error rates, standards governing the technique, and general acceptance are pertinent reliability considerations.
Reasoning
A central question is whether the theory or technique can be, and has been, tested. Testability and falsifiability are important features of scientific methodology because they permit hypotheses to be checked against empirical evidence.
Peer review and publication are relevant because scrutiny by the scientific community can expose methodological flaws. They are not indispensable, however, because a reliable new or highly specialized theory may not yet have been published.
For a particular technique, a court may also consider its known or potential rate of error and whether standards exist to control its operation. Widespread acceptance within the relevant scientific community may support admissibility, while minimal scientific support may justify skepticism.
The trial judge must also remain attentive to other evidentiary rules. Rule 703 limits reliance on inadmissible data to information reasonably relied upon by experts in the field, and Rule 403 permits exclusion when the danger of unfair prejudice, confusion, or misleading the jury substantially outweighs probative value.
Issue #4
Whether the lower courts properly excluded the plaintiffs’ causation evidence and granted judgment based principally on Frye’s general-acceptance standard.
Holding
No. The judgment was vacated and the case remanded because the lower courts relied almost entirely on general acceptance, publication, and prior judicial decisions rather than the reliability-and-fit inquiry required by Rule 702.
Reasoning
The Court did not hold that the plaintiffs’ experts must be admitted or that their evidence ultimately established causation. Rather, it held that the District Court had applied the wrong governing standard and therefore needed to reassess the proffer under Rule 702.
The Court rejected the prediction that replacing Frye would create a free-for-all of pseudoscience. Reliable but disputable testimony may be tested through cross-examination, contrary evidence, jury instructions, Rule 403, and, where the evidence is legally insufficient, summary judgment or judgment as a matter of law.
The Court also acknowledged that gatekeeping can sometimes exclude genuine innovations. But evidentiary rules serve the legal system’s need to resolve particular disputes fairly and finally, not science’s broader and ongoing process of considering every possible hypothesis.