“I believe strongly that the Supreme Court got it [Daubert] right. . . . I think the legal system will get it right.”
—Judge Andre Davis
Beginning in 1993, a series of Supreme Court decisions altered the evidentiary landscape for scientific issues and experts. Prior to 1993, the common standard for admitting expert evidence in federal courts was set by Frye v. United States, a federal appellate court ruling of 1923. This ruling held that expert opinion based on a scientific technique is only admissible if the technique is “generally accepted” in the relevant scientific community.7 General acceptance, however, was sometimes determined on the basis of the testimony of a self-validating expert. The “Supreme Court trilogy,” discussed below, encourages trial judges to decide admissibility not solely on this standard of consensus or general acceptance, but on whether the testimony is grounded in the principles and methods of a particular field.
Daubert began when the parents of two minor children alleged that the children’s birth defects had been caused by the mothers’ prenatal
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The Age of Expert Testimony: Science in the Courtroom - Report of a Workshop 2 The Supreme Court Trilogy “I believe strongly that the Supreme Court got it [Daubert] right. . . . I think the legal system will get it right.” —Judge Andre Davis Beginning in 1993, a series of Supreme Court decisions altered the evidentiary landscape for scientific issues and experts. Prior to 1993, the common standard for admitting expert evidence in federal courts was set by Frye v. United States, a federal appellate court ruling of 1923. This ruling held that expert opinion based on a scientific technique is only admissible if the technique is “generally accepted” in the relevant scientific community.7 General acceptance, however, was sometimes determined on the basis of the testimony of a self-validating expert. The “Supreme Court trilogy,” discussed below, encourages trial judges to decide admissibility not solely on this standard of consensus or general acceptance, but on whether the testimony is grounded in the principles and methods of a particular field. DAUBERT V. MERRELL DOW PHARMACEUTICALS (1993) Daubert began when the parents of two minor children alleged that the children’s birth defects had been caused by the mothers’ prenatal 7 Frye v. United States, 293 F. 1013, 1014 (D.C. Cir. 1923).
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The Age of Expert Testimony: Science in the Courtroom - Report of a Workshop 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; 8 Daubert v. Merrell Dow.
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The Age of Expert Testimony: Science in the Courtroom - Report of a Workshop whether the theory or technique has been subjected to peer review; whether there is a known or potential rate of error associated with the method; and whether the method is generally accepted in the relevant scientific community. These criteria are neither mandatory nor exclusive, as elaborated in Joiner and Kumho below. GENERAL ELECTRIC CO. V. JOINER (1997) In the second case of the trilogy, decided four years later, the Court reinforced the responsibility of the trial judge to screen scientific evidence for the standards of reliability and relevance. Robert Joiner, an electrician in the Water & Light Department in Thomasville, Ga., filed suit in state court, alleging that his small-cell lung cancer had been caused by on-the-job exposure, beginning in 1973, to polychlorinated biphenyls (PCBs) contained in the coolant of electrical transformers. The transformers and the dielectric fluid used as a coolant were manufactured by General Electric and Westinghouse Electric. The Court repeated its opinion that the “austere” Frye standard of “general acceptance” had not been carried over into the Federal Rules of Evidence. In the Joiner case, however, the Court upheld the trial court’s exclusion of certain evidence—not because it was “unacceptable,” but because it was not relevant to the particular case. In particular, it found that the animal studies offered as evidence were too “. . . dissimilar to the facts presented in this litigation,” and that the four epidemiological studies “were not a sufficient basis for the experts’ opinions” regarding this plaintiff’s illness. For example, said the court, “. . . the animal studies involved infant mice that had developed cancer after being exposed to PCBs. The infant mice in the studies had had massive doses of PCBs injected directly into their peritoneums or stomachs. Joiner was an adult human being whose alleged exposure to PCBs was less than the exposure in the animal studies.” In addition, “. . . the cancer that these mice developed was alveologenic adenomas; Joiner had developed small-cell carcinomas.” Finally, “No study demonstrated that adult mice developed cancer after being exposed to PCBs. Weaknesses were also found in each of the epidemiological studies. The Court made clear that in weighing admissibility the judge has the responsibility to ensure that testimony meets the criteria of relevance and reliability. The Court determined that the studies on which the expert’s opinions were based were not sufficiently tied to the issues in the litiga-
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The Age of Expert Testimony: Science in the Courtroom - Report of a Workshop tion, noting that “[N]othing in either Daubert or the Federal Rules of Evidence requires a district court to admit opinion evidence which is connected to existing data only by the ipse dixit [personal opinion] of the expert. A court may conclude that there is simply too great an analytical gap between the data and the opinion proffered.” The Court ruled that the district court judge had not abused her discretion in excluding the scientific evidence. KUMHO TIRE CO. LTD. V. CARMICHAEL (1999) In its ruling in Kumho, two years after Joiner, the Court extended its reasoning beyond the “scientific” evidence of Daubert to all expert testimony based on “skill- or experience-based observation.” The four Daubert factors may be relevant to such evidence, but are not essential; other factors may be appropriate, given the nature of the testimony and the particular circumstances of the case. Thus does Kumho complete the “Daubert trilogy.” The evidence at issue in the case of Kumho was the testimony of an expert in tire failure analysis. The suit began when a worn rear tire of a minivan driven by Patrick Carmichael blew out. In the accident that followed, one of the passengers died, and others were severely injured. The Carmichaels brought suit against the manufacturer, Kumho Tire, claim-ing that the tire was not merely worn but defective, resting their case largely on the testimony of a tire expert. The District Court, referring to the Daubert criteria, disallowed the testimony of the tire expert because it was not considered sufficiently reliable or “scientific.” The Supreme Court agreed that the testimony should be excluded, emphasizing that technical evidence need not be judged by standards appropriate to research results that are published in the scientific literature: “We conclude that Daubert’s general holding—setting forth the trial judge’s general ‘gatekeeping’ obligation—applies not only to testimony based on ‘scientific’ knowledge, but also to testimony based on ‘technical’ and ‘other specialized’ knowledge.”9 The Court made it clear that evidence is to be measured against the level of intellectual rigor that charac-terizes the practice of an expert in the relevant field outside the courtroom, thereby expanding on the four criteria suggested under Daubert for “scientific” evidence. A significant outcome of the opinion was to expand the trial judge’s gatekeeping role to all expert testimony, even testimony that might not be considered “scientific” in a strict sense. In this case, the Court acknowl- 9 Justice Breyer is quoting from Rule 702 of the Federal Rules of Evidence.
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The Age of Expert Testimony: Science in the Courtroom - Report of a Workshop edged that the tire expert was appropriately qualified because of his long experience and expertise, but upheld exclusion of his testimony. The tire expert’s testimony, wrote Justice Breyer, was properly excluded because the expert failed to employ standards used by similar experts who make such assessments outside the courtroom. Following the Kuhmo decision, the Federal Court codified this emerging body of law by amending Rule 702 of the Federal Rules of Evidence, as follows: If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise if (1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts in case.