Daubert vs. Frye: Navigating the Standards of Admissibility for Expert Testimony

If the court deems an expert’s testimony inadmissible, especially suddenly and in the middle of trial, it can have a disastrous effect on the outcome of the case. However, the governing standards of expert witness admissibility are not uniform throughout the United States. States are torn between the two primary admissibility standards: Daubert and Frye.

The two major governing standards can be found in two seminal cases—a D.C. Circuit case, Frye v. United States, 293 F. 1013 (D.C. Cir. 1923), and a U.S. Supreme Court decision, Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993). The federal court system exclusively follows Daubert while state courts are divided between the two. Interestingly, each state has taken on its own interpretation of these two benchmark cases, making the admissibility of expert testimony more variable between jurisdictions. Prior to trial—and ideally, prior to retaining your expert—it’s critical to understand the difference between the Daubert and Frye standards, their specific jurisdictional variations, and any recent, applicable case law.

The Daubert Standard: Enumerated Factors to Consider

In Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), the Supreme Court effectively overruled Frye in federal courts, holding that the case law was inconsistent with the applicable evidentiary rules, namely, Rule 702 of the Federal Rules of Evidence. In Daubert, the Court held that the twin standards of Rule 702—relevance and reliability—are incompatible with the stricter “general acceptance” test.

The Court emphasized the importance of a trial judge’s “gatekeeping responsibility” when admitting expert testimony and listed a non-exhaustive list of factors to consider such as:

1. whether the expert’s technique or theory can be tested and 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
4. the existence and maintenance of standards and controls
5. whether the technique or theory has been generally accepted in the scientific community

Under this new standard, the Court encouraged a more liberal approach to admitting expert testimony, stressing the importance of subjecting witnesses to vigorous cross-examination instead. The decision in Daubert to relax the admissibility standards of expert testimony was further expounded by its progeny. In General Electric Co. v. Joiner, 522 U.S. 136 (1997), the Court emphasized the importance of expert methodology, opposed to focusing solely on the conclusory opinion, finding that “conclusions and methodology are not entirely distinct from one another.”

Importantly, Joiner also set forth the proper standard of review for appellate courts deciding on a district court’s expert testimony evidentiary rulings. Holding that an abuse of discretion standard is appropriate, the Court stated that, “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.” The Court “rejected the notion propounded by several circuits that they should engage in a stringent review of decisions excluding scientific evidence proffered by plaintiffs in toxic tort and product liability cases.”

Less than one year after Joiner was decided, the Supreme Court held in Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999) that the Daubert standard applies to expert testimony that is not scientific in nature. Broadening the range of cases to which Daubert pertains, the Supreme Court held that the standard applies to witnesses that have non-scientific “technical, or other specialized knowledge” as specified in Rule 702. 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.”

The Frye Standard: General Acceptance in the Scientific Community

Unlike the Daubert standard, the general premise in Frye v. United States, 293 F. 1013 (D.C. Cir. 1923) states that an expert opinion is admissible if the scientific technique on which the opinion is based is “generally accepted” as reliable in the relevant scientific community. In Frye, the Circuit affirmed the trial court’s decision to expert testimony concerning a lie detector test. The test, which was based on changes in systolic blood pressure, was considered to have “not yet gained such standing and scientific recognition among physiological and psychological authorities.” What is now referred to as the “general acceptance” test, the Frye standard is aptly described as:

Just when a scientific principle or discovery crosses the line between the experimental and demonstrable stages is difficult to define. Somewhere in this twilight zone, the evidential force of the principle must be recognized, and while the courts will go a long way in admitting expert testimony deduced from a well-recognized scientific principle or discovery, the thing from which the deduction is made must be sufficiently established to have gained general acceptance in the particular field in which it belongs.

Although Frye was decided in 1923, for decades it was not widely followed. The case was not cited for over 10 years following the decision. The standard was increasingly used in the 1970s, predominantly in criminal cases. It then branched itself out into civil cases, such as toxic torts. As the standard gained momentum, so did its criticisms. Some commentators thought that the test was too vague and could not reliably manage complex scientific testimony. In the context of these criticisms, the standard set forth in Daubert emerged.

The Difference Between the Daubert and Frye Standards

Generally, the difference between the Daubert and Frye standards is the broadened approach of the latter. While Frye essentially focuses on one question – whether the expert’s opinion is generally accepted by the relevant scientific community – Daubert offers a list of factors to consider.

Describing the function of trial judges as “gatekeepers,” the factors assist the judges in determining admissibility, while Frye arguably places the decision more in the hands of the expert’s own community. Chief Justice Rehnquist famously noted that the gatekeeping function should not impose on the court “the obligation or the authority to become amateur scientists.” That being said, Daubert does not completely forsake the significance of the “general acceptance” test, as it is included as one of the factors.

Exactly how much weight is to be given to each Daubert factor over another is not explicitly expressed, as the focus is on whether the Court applies a set of criteria that is appropriate in making the necessary evidentiary inquiry. As Justice Scalia noted in Kumho, “the Daubert factors are not holy writ, in a particular case the failure to apply one or another of them may be unreasonable, and hence an abuse of discretion.”

However, testing for reliability is oftentimes the crux of the analysis. As Daubert pointed out, “a key question to be answered…will be whether [an expert’s technique or theory] can be (and has been) tested,” implying the particular importance of the testing for reliability factor. Federal circuits have typically followed suit and explored the reliability factor with more scrutiny than the other factors. For example, in Bielskis v. Louisville Ladder, Inc., 663 F.3d 887, 899 (7th Cir. 2011), the 7th Circuit affirmed the trial court’s exclusion of plaintiff’s engineering expert. The expert, who planned to testify as to a defectively designed scaffold, used Google to search for issues pertaining to his testimony. The Court criticized the experts “shaky proof” and found that he “made no attempt to test his hypothesis.”

When Daubert was first decided, a great deal was made about its analytical differences with Frye. Commentators opined whether the judiciary was equipped to evaluate the merit of scientific testimony and whether it would have an effect on expert admissibility rates. Interestingly, whether the standard does substantially impact the rate of admissibility is still up for debate, with several studies reaching drastically different conclusions.

Likewise, there is not even a consensus as to which standard is stricter. Some courts have found that Daubert and the corresponding Federal Rules of Evidence “favor the admissibility of expert testimony and are applied with a ‘liberal thrust.’” (MBIA Ins. Corp. v. Patriarch Partners VIII, LLC, 2012 WL 2568972, at *15 (S.D.N.Y. July 3, 2012)). While other courts have found that, “Daubert assigned district courts a more vigorous role to play in ferreting out expert opinion not based on the scientific method.” (Cavallo v. Star Enterprise, 892 F. Supp. 756, 774 (E.D. Va. 1995)).

As Daubert applies to all federal courts, the differences between the two standards are more aptly seen in the state court context. A number of states continue to use the Frye general acceptance test, while the states that have adopted Daubert (approximately 27) have not all uniformly applied the standard. Only nine states have adopted Daubert in its entirety, while other states have their own completely different standard of admissibility. Overall, the evidentiary standard governing the admissibility of expert testimony is, in many respects, a continuum opposed to a bright-line rule.