United States Supreme Court

509 U.S. 579 (1993)

Nature of Case

Federal standard for admitting expert testimony.


Facts of Case

Two minors and their guardians brought suit against Merrell Dow Pharmaceuticals in a California state court alleging that their antinausea medication, Bendectin, caused serious birth defects when ingested by pregnant women. The suit was removed, on diversity grounds, to the United States District Court for the Southern District of California.

Experts for the plaintiffs presented data that had not been published or subjected to peer review and their opinions rested on the reanalysis of previously published data.

The United States District Court for the Southern District of California granted the defendant’s motion for summary judgment on the grounds that the petitioners’ expert opinions were inadmissible, because the reanalysis was unreliable due to it being unpublished and evidence was only admissible under the Federal Rules if it was sufficiently established to have gained general acceptance in the field. On appeal to the United States Court of Appeals for the Ninth Circuit, the district court’s summary judgment for the defendant was affirmed. The plaintiffs petitioned for writ of certiorari and the United States Supreme Court granted the petition.



Did the district court and the United States Court of Appeals for the Ninth Circuit err in excluding the petitioners’ expert testimony by incorrectly requiring the testimony to meet Frye’s general acceptance standard?



In a unanimous decision, the United States Supreme Court held that the Federal Rules of Evidence, not Frye, provide the standard for admitting expert scientific testimony in a federal trial. According to the Court’s decision, general acceptance in the field is not a prerequisite for admissibility of scientific testimony or evidence, so long as the standards of reliability and relevance under the Federal Rules were met. The Federal Rules assign the judge the task of identifying whether the basis for the expert’s testimony is scientifically valid and can be properly applied to the facts at issue. In assessing whether the underlying reasoning is valid and relevant, the judge, acting as gatekeeper, may consider the following:

  1. Whether the theory or technique in question can be (and has been) tested.
  2. Whether it has been subjected to peer review and publication.
  3. Whether the known or potential error rate is acceptable.
  4. Whether it has attracted widespread acceptance within a relevant scientific community.

The Court vacated the appellate court’s affirmance of summary judgment in favor of the defendant and remanded the case for further proceedings.


The Federal Rules of Evidence, adopted in 1975, superseded the general acceptance common law standard from the 1923 D.C. Circuit Court’s decision in Frye v. United States. While general acceptance can be considered, it is not required. The application of the Federal Rules was to allow judges more flexibility and broader discretion in the admissibility of testimony and to allow for the inclusion of novel evidence that may be scientifically valid and reliable, but not yet generally accepted in the field.