ingestion of Bendectin, a prescription anti-nausea drug marketed by Merrell Dow. A district court accepted the affidavit of an expert who reviewed the scientific literature on the subject and concluded that mater-nal use of Bendectin had not been shown to be a risk factor for human birth defects.
The court disallowed the evidence of eight other experts who argued that Bendectin could indeed cause birth defects. The evidence of these experts was based on animal studies, chemical structure analyses, and the unpublished “reanalysis” of previously published human statistical studies. The court, citing Frye, stated that expert opinion that is not based on epidemiological evidence is not admissible to establish causation. Therefore, the evidence of the eight experts, ruled the court, was not admissible because it was not “sufficiently established to have general acceptance in the field to which it belongs.” The Court of Appeals for the Ninth Circuit agreed.
The Supreme Court vacated and remanded this judgment for further proceedings, ruling that the enactment of the Federal Rules of Evidence in 1975 superceded the general acceptance test of the then-50-year-old Frye test. The Court pointed to Rule 702, which permits experts to testify on matters of “scientific, technical or other specialized knowledge” if it will assist the judge or jury to understand the evidence. The rule also places “appropriate limits” (in the words of Justice Blackmun) on the admissibility of purportedly scientific evidence by assigning “to the trial judge the task of ensuring that an expert’s testimony both rests on a reliable foundation and is relevant to the task at hand. Pertinent evidence based on scientifically valid principles will satisfy those demands.”8
The Court reasoned that, if expert testimony is offered in the form of “scientific . . . knowledge,” that testimony must be based on a reliable scientific methodology. Under the Rules, the trial judge is now responsible for assessing both its relevance and reliability. The subject of an expert’s testimony must, according to Daubert, be “scientific . . . knowledge,” and this knowledge must be grounded in the methodology and reasoning of science.
This decision imposes a considerable “gatekeeping” responsibility on federal trial judges and provides guidance, in the form of four suggested factors, for screening expert scientific testimony. The four “Daubert criteria” for evaluating the admissibility of expert testimony are:
whether the theories or techniques upon which the testimony relies are based on a testable hypothesis;