A Brief History of the Expert Witness
(This is a brief excerpt from Edition 1 of The Expert Witness Handbook.)
According to law.com’s legal dictionary, an expert witness is “a specialist in a subject, often technical, who may present his/her expert opinion without having been a witness to any occurrence relating to the lawsuit…”
Those lines highlight important differences between expert witnesses and fact witnesses. Fact witnesses may testify about what they personally saw and heard, but they may not elaborate on their opinions. Expert witnesses, on the other hand, discuss underlying issues and educate the court about them. For example, an expert witness may assist with evaluating economic damages by opining on the future earnings of the plaintiff in a given field, or they may help a jury understand the variations in how a drug is evaluated by the appropriate regulatory agencies of two different countries.
Experts in English Common Law and Beyond
Forensic experts have been part of the judicial process since at least the Roman Empire, which recognized handwriting experts, land surveyors, and midwives as legal experts. Experts appeared in English courts as early as the 16th century. Artisans and merchants were presented as neutral advisors, explaining the unique standards of their trades, while physicians and surgeons helped explain evidence in criminal cases.
Early on, English judges directly examined the parties and witnesses. Over time, the roles of prosecutors and defense attorneys increased. Though defense counsel could not initially address the jury, they were able to examine witnesses, developing the first techniques of cross-examination, and influence evidence given to the jury. As the adversarial roles of prosecutor and defense evolved, both began summoning their own, potentially partisan, experts.
By the late eighteenth century, some standards for witnesses had emerged. The ‘opinion doctrine’ required witnesses to speak factually, rather than inferentially, where possible. The ‘hearsay doctrine’ attempted to limit testimony to that which was personally observed. What we now call expert witnesses ended up as the exceptions to these rules—they could pronounce an opinion in court without observing the facts of the case personally—though they were still expected to rely exclusively on direct observational data.The Foundations of Rules Governing Expert Evidence
By the end of the eighteenth century, courts were faced with an important new kind of expert, the ‘scientist’ (though that word wasn’t coined until 1834) who fueled Britain’s industrial revolution through philosophical reasoning, mathematics, observational analysis, and trying to uncover the previously hidden laws of nature.
Folkes v. Chadd (1782) established the foundation for admitting expert opinions as evidence in English common law, carving out a specific place for scientific thought in the courtroom. Wells Harbour, an important tidal waterfront in Northern England, had silted up. After several attempts to rehabilitate the harbor failed, the harbor’s board of commissioners took legal action, alleging reclamation of land by a large local landowner (Folkes) had caused the harbor failure, and Folkes’ embankment should be removed.
In the 1782 trial, the commissioners presented a variety of traditional maritime experts to describe their observations of the harbor’s rapid deterioration after construction of the Folkes embankment. The landlord’s lawyers’ sole expert, Robert Mylne, a famed London-based engineer, explained how the harbor had silted up because of logical, natural causes rather than the introduction of the embankment.
When the jury found for Folkes based on Mylne’s persuasive testimony, the commissioners’ lawyers moved for a new trial alleging Mylne’s explanations were too theoretical to be consistent with opinion doctrine and shouldn’t have been permitted. A new trial was set for the following summer. To avoid additional surprises, the judges asked the parties to exchange any expert opinions upon which they intended to rely in court.
In the second trial, the harbor commissioners hired several well-known engineers and surveyors who measured and mapped the lengths, depths, winds and tides of the Wells estuary. Folkes’ team added one more expert: John Smeaton, considered England’s foremost expert on harbors. Smeaton’s report included a theoretical explanation of the principles underlying creation and decay of tidal harbors. At trial, the Harbor Commission asserted Smeaton’s testimony should be excluded, since the laws of nature were a “matter of opinion, which could be no foundation for the verdict of the jury, which was to be built entirely on facts, and not on opinions.”
The Chief Justice of the Royal Court of Common Pleas, Justice Gould, accepted that argument. Smeaton was not allowed to testify, and the Harbor Commission prevailed in the second trial. Citing their star witness’ exclusion, Folkes’ lawyers appealed the ruling.
Where Justice Gould had viewed Smeaton’s testimony as too speculative, the eminent Lord Mansfield, Chief Justice of the King’s Bench, to whom the third trial came, was unwilling to accept an approach which denied the court the opinion of the country’s foremost harbor expert: “I cannot believe that where the question is, whether a defect arises from a natural or an artificial cause, the opinions of men of science are not to be received…”
Lord Mansfield argued that even the commissioners in the original case were proposing opinions (for instance, “The embankment was preventing the backwater.”) and if so, Lord Mansfield wanted to rely on experts to help the court weigh the possible explanations. To Lord Mansfield, if the proposed witness was known as an expert on the matter at hand, his opinion was proper evidence. In retrospect, Lord Mansfield’s decision in Folkes v. Chadd made the opinions of relevant scientists an exception to the opinion doctrine, and significantly expanded the potential purview of experts in English and, consequently, American courtrooms.
With Smeaton’s testimony that the silting of the harbor was caused by activities upriver from Wells, Folkes’ team prevailed.
Expert Battles: Who Can You Trust?
To Lord Mansfield, ‘renowned in the field’ sufficed to recommend an expert’s testimony. Late 18th century judges counted upon gentlemen (almost all the first wave of English ‘scientists’ were gentlemen) to be truthful and honorably unbiased. If a person was qualified in a relevant field and their opinion was helpful to evaluating the facts of the case, they could be heard.
As legal use of scientific expertise grew, frustration with varied opinions of scientific experts grew. Expert battles arose, as both sides of cases lined up eminent scientists to put forth contradictory experimental evidence and overwhelm the ability of judge and jury to determine whose opinion to trust. What does it mean when methodologies and interpretations of results lead to contradictory conclusions?
Neither lawyers nor experts relished the situation. A popular joke in legal circles of the day was “There are three kinds of liars — the common liar, the damned liar, and the scientific expert.” Legal historian James Fitzjames Stephen’s 1863 A General View of the Criminal Law of England, paints a picture of experts as hired guns: “No one expects an expert, except in the rarest possible cases, to be quite candid. Most of them – are all but avowedly advocates, and speak for the side which calls them.”
The reform of expert testimony was a recurrent hot topic in both legal and scientific circles. In the U.S., juries were largely left to their own devices to sort out valuable experts from charlatans. In 1905, Michigan passed a reform allowing the court to provide its own experts, but the Michigan Supreme Court soon held the statute unconstitutional.
What expert evidence should juries believe? An increasingly partisan legal system required more specific guidance. There was some agreement that professional codes of training and practice, increasingly common for the various sorts of experts who might appear in a courtroom, might be part of the solution, but how that would work was unclear. By 1922, there was still no better guidance for the admissibility of scientific evidence.
The Frye Standard (1923)
That year, a young man named James Frye was accused of murdering a prominent doctor. As part of Frye’s defense, his attorney put forward the results of a systolic blood pressure “lie detector” test and William Marston, the test’s inventor, as evidence of his innocence. But Judge Walter Irvin McCoy refused to admit Marston and his test into evidence. When Frye was found guilty, his attorney appealed, arguing that a scientific expert and evidence had been improperly excluded.
On hearing Frye’s case, the District of Columbia Court of Appeals reframed the discussion in an innovative and important way: Rather than focusing only the expert’s credentials, it suggested courts should evaluate on the particular scientific theories being advanced—how well-established were they? This became the Frye Standard: 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.
The General Acceptance test in Frye v. United States was not widely adopted right away; the case was not even cited in any other case for a decade following the decision, but it eventually became the broad and influential standard for expert admissibility in both criminal and civil cases in the U.S., helping courts discriminate between mere hypothesis and well-established scientific theories.
The Federal Rules of Evidence (1975)
Congress muddled the issue in enacting the Federal Rules of Evidence in 1975. Its Rule 702 outlines the admissibility of experts:
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.
Despite appearing a half century after Frye, the Federal Rules of Evidence were in some ways a return to a previous wild west of expert admissibility: they notably failed to explain which kinds of scientific, technical, or other specialized experts, if any, should not be allowed to appear in the courtroom.
Rule 702 opened the door for a broader variety of expert usage, but since it didn’t explicitly tell courts to abandon the Frye rule, many federal and state courts continued to evaluate the admissibility of scientific evidence using Frye’s General Acceptance criteria.
The Daubert Standard (1993)
Despite its inconsistency with Rule 702, Frye’s General Acceptance test continued to gain momentum. But some believed there ought to be more specific guidance.
Daubert v. Merrell Dow Pharmaceuticals (1993) set a new standard for expert witness admissibility. When Jason Daubert and Eric Schuller were born with severe birth defects, their parents took legal action against Merrell Dow Pharmaceuticals Inc., a subsidiary of Dow Chemical Company, asserting the drug Bendectin was responsible for causing the birth defects.
Merrell Dow sought summary judgment. The company’s expert testified that no published scientific study had established a connection between Bendectin and human birth defects.
However, the plaintiffs submitted evidence based on in-vitro and in-vivo animal studies, pharmacological studies, and other methodologies purporting to show otherwise. The plaintiff’s evidence had yet to gain acceptance within the general scientific community, but the Supreme Court ruling in Daubert allowed it, setting the court up to be the gatekeeper for admitting expert testimony based on a broader list of criteria to consider, such as:
Can the expert’s technique or theory be tested and assessed for reliability? Has the technique or theory been the subject of peer review and publication? What is its known or potential error rate? Are there standards for this technique? Has the technique or theory been generally accepted in the scientific community?
[Sidebar – How to pronounce Daubert]
According to the attorney representing petitioners Jason Daubert and Eric Schuller many years ago (Michael Gottesman), the family pronounced their surname “DOW-burt.”. However, when one of the supreme court justices mispronounced the name as “Dough-BEAR,” following how it might be pronounced in France, he didn’t correct him, instead focusing on the facts of the matter at hand. The remaining justices then assumed “Dough-BEAR” was correct.
In the end, in the 1994 article “Admissibility of Expert Testimony After Daubert: The “Prestige” Factor” (43 Emory L.J. 867), Gottesman notes:
Let me, then, use this occasion to make amends to my clients. The family’s name is not dough-bear. Whether this will (or should) affect the way people pronounce the name of the Supreme Court’s opinion is, of course, another matter. Do the litigants or the Court own title to the pronunciation of the name of a Court opinion?
Expert Witness Standards Continue to Evolve
General Electric Co. v. Joiner (1997) broadened trial judges’ gatekeeping role around expert evidence. Following Joiner, a trial court can now not only evaluate an expert’s methodology, but also question the conclusions of experts when determining admissibility: Judges may also review the research data and studies upon which an expert relies and evaluate whether they believe those studies support the asserted opinion.
In Kumho Tire Co. v. Carmichael (1999), the Supreme Court significantly expanded Daubert in U.S. Courts, holding that the Daubert standard applies to technical and other specialized expert testimony which is not purely scientific. As a result, the scope of expert testimony in complex legal proceedings is broader than ever, allowing courts to benefit from experts in more fields.
Standards surrounding expert witnesses continue to evolve (for instance, the Supreme Court sent proposed changes to rule 702 to Congress in 2023, taking effect in December of that year), and various courts differ in the rules followed and interpretations. As expert witnesses continue to exert strong influence over judgements, courts will continue to hold them under a microscope and study their effects.
Warning: Standards Differ by Jurisdiction
While Daubert is the standard in federal courts, different federal courts must interpret these standards. Additionally, not all state courts follow the Daubert standard. There are still some, such as California, Illinois, New York, Washington, Minnesota, and Pennsylvania that generally follow some version of Frye. Many states have implemented a version of Daubert, and yet others are either in-between, or have their own testing method. The attorney must be conversant with the standards for expert witnesses in the given courtroom. Moreover, experts should know the Daubert and Frye standards, as those tend to be the baselines—but follow the advice of the attorney you are working with for the rules of the particular court, (and possibly judge) before whom you will appear.
We’re hard at work on Edition 2 of The Expert Witness Handbook at the Expert Witness Club. Come join us there to access the updated content, and help us create an even more useful resource for experienced expert witnesses.