The Daubert Trilogy: Navigating the Standard for Expert Witness Challenges

When the Supreme Court set the standard for expert testimony admissibility in the seminal case, Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), it was a precedential turning point. However, the current standard, though founded by the Daubert Court, is also deeply rooted in its progeny. Referred to as the Daubert trilogy, the two cases that came after Daubert greatly contributed to the final standard used today to admit expert testimony. While the Court in Daubert enumerated the factors to be considered when evaluating the reliability of expert testimony, General Electric Co. v. Joiner, 522 U.S. 136 (1997) addressed the appellate standard of review of a trial court’s admissibility ruling. Finally, Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999), the Court applied the Daubert standard to nonscientific expert testimony. Taken together, these three cases have crafted the current standard for expert testimony admissibility.

The Significance of Daubert

Prior to the Daubert decision, the admissibility of expert testimony was governed by the Frye standard. In Frye v. United States, 293 F. 1013 (D.C. Cir. 1923), the Court held that expert witness testimony was inadmissible unless the principle had gained “general acceptance” in its field. The Frye standard of general acceptance is still used in certain state jurisdictions. While the Daubert standard is adopted in all federal courts, codified in Rule 702 of the Federal Rules of Evidence.

In contrast with Frye, the Daubert Court held that expert testimony is not required to be generally accepted within the scientific community. Rather, admissibility must be based on the relevance and reliability of the evidence sought to be admitted. First, the evidence must qualify as relevant under Rule 702; which states the expert’s testimony must “help the trier of fact to understand the evidence or determine a fact in issue”. Secondly, the evidence must be reliable. The Court enumerated a nonexclusive list of factors for the trial judge to consider in determining whether the evidence is sufficiently reliable to be admitted.

These factors include:

1. whether the expert’s technique or theory can be or has been tested; that is, whether the expert’s theory can be challenged in some objective sense, or whether it is instead simply a subjective, conclusory approach that cannot reasonably be assessed for reliability
2. whether the technique or theory has been subject to peer review and publication
3. the known or potential rate of error of the technique or theory when applied and the existence and maintenance of standards and controls
4. whether the technique or theory has been generally accepted in the scientific community

Unlike the Frye standard, the Daubert Court set forth a more flexible “inquiry envisioned by Rule 702”. Also, the Court stressed the importance of the trial judge’s “gatekeeping function” in admitting expert testimony. The Daubert standard and its non-exclusive factors provided flexibility. However, it also opened the doors for additional questions that were subsequently decided by its progeny.

General Electric Co. v. Joiner:  Appellate Review and the Importance of Conclusions

The holding in General Electric Co. v. Joiner, 522 U.S. 136 (1997), a toxic tort case which excluded the plaintiff’s expert witnesses, is significant in two ways. First, Joiner clarified the holding in Daubert that expert methodology, opposed to the conclusion, should be the focus of the inquiry. While acknowledging the importance of an expert’s techniques, Joiner noted that “conclusions and methodology are not entirely distinct from one another”. As the Joiner Court explains:

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Trained experts commonly extrapolate from existing data. But nothing 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 [unsupported statement] of the expert. A court may conclude that there is simply too great an analytical gap between the data and the opinion proffered.

In other words, while Daubert stressed the importance of methodology, rather than the accuracy of an expert’s conclusion, Joiner narrowed this line of analysis. While admissibility is not solely hinged on an expert’s ability to reach an accurate conclusion; Joiner holds that it must nonetheless correlate with supportive data.

The second important aspect of Joiner is it held that abuse of discretion is the proper standard of review of the district court’s expert testimony evidentiary rulings. As Joiner explained, “while the Federal Rules of Evidence allow district courts to admit a somewhat broader range of scientific testimony that would have been admissible under Frye, they leave in place the ‘gatekeeper’ role of the trial judge in screening such evidence”. As such, Joiner “rejected the notion propounded by several circuits that they should engage in especially stringent review of decisions excluding scientific evidence proffered by plaintiffs in toxic tort and product liability cases.”

Kumho Tire Co. v. Carmichael and Non-Scientific Evidence

Less than one year after its holding in Joiner, the Supreme Court granted certiorari in Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999), to decide if the trial court’s gatekeeping responsibility under Daubert only applied to scientific testimony or if it extended to “technical, or other specialized knowledge” as specified in Rule 702. Since the holding in Daubert, a split had developed among the circuit courts as to whether the factors could be used to determine the admissibility of other disciplines or expertise, such as economics, psychology, and other “soft sciences”. Because Daubert focused on the reliability and methodology of the evidence, some courts believed it only applied to strictly scientific techniques that could be easily tested.

In Kumho, the plaintiffs brought suit against a tire distributor; after a tire blew out and caused an accident which killed a passenger and injured others. The plaintiff’s expert, a tire failure analyst, was excluded after the district court found the evidence did not satisfy the Daubert factors. The 11^th Circuit reversed, holding that the lower court erred by applying Daubert to a nonscientific expert.

The Supreme Court, however, held that the district court was correct in applying the Daubert factors to the tire analyst. Thus broadening the range of experts the standard covers. The Court found no relevant distinction between experts who rely on scientific principles and those who rely on “skill- or experienced-based observation”. Citing Rule 702 of the Federal Rules of Evidence, which also makes no distinction between scientific knowledge and “technical or other specialized knowledge”.  Therefore, the Kumho Court held that the Daubert factors for relevance and reliability may be applied to all expert testimony.

The Future for Expert Testimony Admissibility

Although the Daubert trilogy of Supreme Court cases, as codified in Rule 702, has established the standard of admissibility of expert testimony in federal court, the governing rule in state courts is far more unsettled. A number of states continue to use the Frye general acceptance test. While the states (approximately 27 of them by 2003) that have adopted Daubert have not all uniformly applied the standard. Only nine states have adopted the Daubert trilogy in its entirety. While others have accepted it piecemeal, following either none, one, or only a part of Daubert’s successor cases.

Even within the federal system, the Daubert trilogy has left, quite possibly by design, a number of unanswered questions. As held in the last case of its trilogy, the broad scope and open-ended nature of Kumho guarantees that the admissibility of expert testimony will continue to evolve. Particularly as the breadth of science and other nonscientific fields develop, and more experts advance in these areas; it is safe to assume that the body of case law will also need to continuously grow. But for now, an understanding of the Daubert trilogy is essential to the survival of any expert witness testimony.