The Center for Truth in Science is committed to a world where decisions are made with the best knowledge and evidence to ensure a just and healthy world. With this in mind, we recognize that scientific assessment of causation and risk are essential in the litigation and regulation of health effects. The Center’s interest in fostering high-quality systematic reviews of health effect claims inevitably involves us in cutting-edge controversies, whether in court or in agencies. As citizens and scientists, we are interested in making sure that the scientific assessments of health effects are made with good and sufficient evidence and valid inferences.
The court system of the United States has not always been conducive to sound scientific judgments. In the common law of the 19th and early 20th centuries, courts required expert witness testimony on an issue when the subject matter was beyond the ken of the ordinary juror. The expert witnesses seeking to testify needed to be qualified by training, education, or experience, and their opinions needed to be only relevant to the issues in the case. Courts exercised minimal control over the substance of testimony, once the witness was shown to be qualified. The fact finder, usually a lay jury, was free to accept or reject the expert witness opinion testimony offered in court. This era of expert witness testimony might well be characterized as a laissez-faire judicial regime, in which courts deferred to expert witnesses and juries, without supervising the quality or sufficiency of underlying facts and data, or the validity of inferences. At common law, upon being found qualified, expert witnesses were under no obligation to comply with the ethical or substantive requirements of their discipline. Indeed, with the benefit of hindsight, the common law approach can be seen as an authoritarian standard, under which the possession of some credentials entitles the bearer to hold forth as an expert witness at trial.
This simple regime may have worked reasonably well when expert witnesses mostly offered general principles of science, which the jury could understand and apply to the particular facts of a case. In 1923, an intermediate federal appellate court announced an exclusionary rule for a limited category of expert witness opinion testimony found to be “novel” and “not generally accepted.” The famous Frye case involved an appeal from a trial court’s exclusion of an expert witness opinion based upon William Marston’s lasso of truth, the polygraph machine. The exclusion of the opinion based upon Marston’s primitive polygraph based upon the lack of general acceptance of the device’s reliability, with some colorful language about the twilight zone:[1]
“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 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.”
This holding became known as the Frye general acceptance test, which courts generally limited to criminal cases involving novel devices. The test was apparently a sociological test in calling for evidence of general acceptance or consensus, which might be satisfied by a survey of opinions in a particular field, without inquiring into whether the opinions were well founded. The test had other obvious problems, such as an inherent ambiguity as to whether it was the opinion or its underlying methodology that was generally accepted.
The law of expert witness opinion testimony changed dramatically in 1975, with the adoption of the Federal Rules of Evidence, which apply in all federal courts. In this codification process, the admissibility of expert witness testimony was addressed by Rule 702, which introduced a subtle, aspirational criterion for expert witness opinion – knowledge. As originally enacted, Rule 702 read:
“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.”[2]
In case anyone missed the significance of the Rule’s use of “knowledge,” the drafters on the Advisory Committee, emphasized that they intended for the standard to be an epistemic standard:
“An intelligent evaluation of facts is often difficult or impossible without the application of some scientific, technical, or other specialized knowledge. The most common source of this knowledge is the expert witness, although there are other techniques for supplying it.”[3]
The imposition of a requirement that the proffered opinion be an “intelligent evaluation of facts,” reached by the application of some form of knowledge, introduced a new, epistemic criterion, above and beyond mere relevancy, for expert witness opinion testimony.
The passage of the Rules by Congress did little, at first, to change how courts treated expert witness testimony. The 1970s and 1980s saw an explosion of tort litigation, often based upon controversial health claims. Lawyers attempted to press Frye’s requirement of general acceptance into service as a bulwark against invalid scientific opinions. Most courts, however, limited the Frye rule to novel devices, and they showed no enthusiasm for putting any teeth into Rule 702’s requirement of knowledge.
The laissez-faire era came to an end with the landmark decision of the Supreme Court, in 1993, in a case known as Daubert.[4] Technically, the holding of the case rejected the legal claim that Rule 702 had incorporated the Frye “general acceptance” test. More important for subsequent legal practice, the Supreme Court clearly held that Rule 702 laid down an epistemic test, not a call for sociological surveys about the prevalence of beliefs.
In the next few years after the Daubert case, the Supreme Court decided three more cases to emphasize that the epistemic standard was “exacting” and that it would not go away.[5] In one of those cases, Kumho Tire, Justice Breyer, writing for the court, gave an alternative expression to the clearly epistemic goals of Rule 702, which was “to make certain that an expert, whether basing testimony upon professional studies or personal experience, employs in the courtroom the same level of intellectual rigor that characterizes the practice of an expert in the relevant field.”[6] This articulation ensures that the epistemic standards of the discipline are imported into the admissibility determinations by courts. Justice Breyer’s formulation also emphasizes the importance of the scientific community’s involvement in the judicial expert witness gatekeeping process.
The published study is the typical building block for expert witness opinion in litigation of health claims. Now that the admissibility standards for expert witness opinion testimony requires attention to the sufficiency of the expert witnesses’ facts and data, to the validity of their methodology, and to the validity of their application of their methodology to the facts of cases, lawyers must pay attention to the presence of questionable research practices and become more sophisticated consumers of, and advocates for, good science. Law and science have converged in their concerns for validity concerns in studies, and in drawing causal conclusions. We at the Center have accordingly weighed in on the resolution of scientific issues in court.
In 2000, in the wake of the Supreme Court’s quartet of decisions, Rule 702 was amended substantively to incorporate the essence of the Supreme Court’s observations about the necessary requirements for the admissibility of expert witness opinion testimony,[7] such as the requirement that the proponent of an opinion establish that it is based upon sufficient facts or data, is the product of reliable principles and methods, and is the result of reliably applying those reliable principles and methods to the facts of the case. Last year, Rule 702 was amended yet again, to address judicial resistance to the requirement of gatekeeping expert witness opinions.
With the salutary reform of expert witness testimony, the days of “easy admissibility” for dodgy expert witness testimony should be confined to the dustbin of legal history. The situation in many state courts is less sanguine. As with liberty, the price of truth is eternal vigilance. We are watching.
[1] Frye v. United States, 293 F. 1013, 1014 (D.C. Cir. 1923).
[2] Pub. L. 93–595, § 1, Jan. 2, 1975, 88 Stat. 1937 (emphasis added).
[3] Notes of Advisory Committee on Proposed Rules (1975) (emphasis added).
[4] Daubert v. Merrell Dow Pharm., Inc., 509 U.S. 579 (1993).
[5] General Electric Co. v. Joiner, 522 U.S. 136 (1997); Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999); Weisgram v. Marley Co., 528 U.S. 440 (2000).
[6] Kumho Tire, 526 U.S. at 152.
[7] See notes 5, 6, supra.