A Brief History of Expert Witnesses in U.S. Courts

Expert witnesses appear sparingly in American and English court records from as early as 1782, and professionals have helped lawyers prepare their cases for at least as long. Yet the use of experts to testify in U.S. court cases did not become widespread until the twentieth century.

In the 1920s, psychologists were called to testify in several U.S. cases, including Coca-Cola Company v. Chero-Cola Company, in which a psychologist gave expert testimony as to whether Chero-Cola’s trademark would cause confusion for consumers by being too similar to Coca-Cola’s trademark. Physicians and psychiatrists were also asked to testify as experts, often in criminal cases.

In 1923, the question of how to evaluate the expertise of these “experts” came to a head.

1923 to 1975: Courts Ask What It Means to be “Generally Accepted”

In 1923, the case of Frye v. United States changed both criminal and civil law by addressing not only an issue in criminal cases – the use of polygraph tests – but also the use of expert witness testimony. In Frye, the defense attempted to introduce both the results of a polygraph test to demonstrate Frye’s innocence and the testimony of an expert witness to explain those results.

The court rejected the expert’s testimony:

“[W]hile 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.”

By making this statement, the Frye court not only explained its own reasoning but also set the standard by which expert witnesses would be evaluated for years to come.

Yet that standard was not immediately embraced. States adopted Frye on their own timetables and to the extent it suited them. In the federal courts, Frye was cited 55 times between 1948 and 1975, yet its application was not always consistent. Courts struggled to determine whether Frye applied to all experts and whether it applied to both civil and criminal cases. Many had trouble interpreting “general acceptance” in a clear and consistent manner.

1975: The Federal Rules of Evidence Provide (The Opposite Of) Clarity

In 1975, Congress issued the Federal Rules of Evidence (FRE). FRE 702 provided a standard for expert witness testimony that answered some of the stickiest questions related to Frye. The rule specified that it applied to “scientific or technical knowledge,” it listed potential qualifications as an expert in terms of “knowledge, skill, experience, training or education,” and it clearly applied to civil cases.

Yet FRE 702 still left some courts in confusion. While it could be read to clarify Frye, neither the rule itself nor its explanatory notes even mention Frye. Was FRE 702 meant to support Frye or replace it?

In U.S. v. Williams, the Second Circuit responded that “the applicable considerations [for expert witness testimony] are ‘probativeness, materiality, and reliability of the evidence on the one side, and any tendency to mislead, prejudice or confuse the jury on the other.’” The Williams court rejected the evidence before it as “junk science,” and in doing so, it appeared to reject Frye’s “general acceptance” standard as well.

The reasoning in Williams was adopted by other federal courts, including the Third Circuit. In 1984, the Third Circuit cited Williams in U.S. v. Downing, which adopted a “reliability” test in lieu of Frye’s “generally accepted” test. Meanwhile, other federal courts stuck to Frye, creating a circuit split the U.S. Supreme Court would eventually resolve.

1993: The U.S. Supreme Court Weighs In

In 1993, the U.S. Supreme Court granted cert in Daubert v. Merrell Dow Pharmaceuticals, agreeing to hear the case. Plaintiffs Jason Daubert and Eric Schuller and their parents had sued Merrell Dow Pharmaceuticals, claiming that the company’s drug, Benedictin, had caused Daubert and Schuller to be born with serious birth defects.

To make their case, the plaintiffs offered expert evidence that Benedictin was linked to birth defects. This evidence, however, was based on study methods that were not, at the time, “generally accepted” in the scientific community.

The case thus presented a strong vehicle for addressing the expert standard: Should expert evidence and testimony be “generally accepted,” or should it meet some other set of requirements?

The Supreme Court merged these two routes. Echoing Williams and Downing, the Court provided four guidelines for considering expert witness testimony:

1. Whether the expert’s theory or technique can be (and has been) tested
2. Whether the theory or technique has an acceptable known or potential rate of error
3. The existence and maintenance of standards controlling the technique’s operation
4. Whether the theory or technique has attained “general acceptance”

Daubert became the federal standard for evaluating expert witness testimony. State courts, however, were allowed to continue to set their own course. Over the years since Daubert, many states have adopted the standard, although a handful still continues to rely either on Frye or on their own particular state standard.

1999: Who Counts as an Expert for Daubert?

One question Daubert did not answer was which expert witnesses had to be evaluated according to the case’s standards. Did Daubert apply only to “scientific and technical” witnesses and subjects, as FRE 702 indicated?

In Kumho Tire Co. v. Carmichael, the U.S. Supreme Court answered this question by holding that the Daubert standard applies to any expert witness in federal court, whether their testimony was scientific, technical, or otherwise. However, the court also held that trial courts can consider factors outside Daubert, particularly if doing so would enhance the trial court’s ability to perform its gatekeeping function.

Today, Daubert remains the standard in all federal and most state courts. Understanding how Daubert’s evaluation applies can help an expert witness tailor testimony and reports to maximize both the judge’s and jury’s understanding of the value of the expert’s work.