The 1975 codification of the law of evidence, in the Federal Rules of Evidence, 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 As originally enacted, Rule 702 read: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.”[1]
In case anyone missed the point, the Advisory Committee Note for the original Rule 702 emphasized that the standard was 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.”[2]
Perhaps we should not be too surprised that the epistemic standard was missed by most judges, and even by most lawyers. For a very long time, the common law set out a minimal test for expert witness opinion testimony. The expert witness had to be qualified by training, experience, or education, and the opinion proffered had to be logically and legally relevant to the issues in the case.[3] The enactment of Rule 702, in 1975, barely made a dent in the regime of easy admissibility.
Before the Federal Rules of Evidence, there was, of course, the famous Frye case, which involved an appeal from the excluded expert witness opinion based upon William Marston’s polygraph machine. In 1923, the court in Frye affirmed the exclusion of the expert witness opinion, based upon the lack of general acceptance of the device’s reliability, with its famous twilight zone language:[4]
“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.”
With the explosion of tort litigation fueled by strict products liability doctrine, lawyers pressed Frye’s requirement of general acceptance into service as a bulwark against unreliable scientific opinions. Many courts, however, limited Frye to novel devices, and in 1993, the Supreme Court, in Daubert,[5] rejected the legal claim that Rule 702 had incorporated the common law “general acceptance” test. Looking to the language of the rule itself, the Supreme Court discerned that the rule laid down an epistemic test, not a call for sociological surveys about the prevalence of beliefs.
Resistance to the spirit and text of Rule 702 has been widespread and deep seated. After Daubert, the Supreme Court decided three more cases to emphasize that the epistemic standard was “exacting” and that it would not go away.[6] Since Daubert was decided in 1993, Rule 702 was amended substantively, in 2000, to incorporate some of the essence of the Supreme Court’s quartet,[7] which required the proponent of expert witness opinion to establish that proffered testimony is based upon sufficient facts or data, is the product of reliable principles and methods, and the result of reliably applying those reliable principles and methods to the facts of the case.
The change in the law of expert witnesses, in the 1990s, left some academic commentators well-nigh apoplectic. One professor of evidence law at a large law school complained that the law was a “conceptual muddle containing within it a threat to liberty and popular participation in government.”[8] Many federal district and intermediate appellate courts responded by ignoring the language of Rule 702, by reverting to pre-Daubert precedent, or by inventing new standards and shifting the burden to the party challenging the expert witness opinion’s admissibility. For many commentators, lawyers, and judges, science had no validity concerns that the law was bound to respect.
The judicial evasion and avoidance of the requirements of Rule 702 did not go unnoticed. Professor David Bernstein and practicing lawyer Eric Lasker wrote a paper in 2015, to call attention to the judicial disregard of the requirements of Rule 702.[9] Several years of discussion and debate ensued before the Judicial Conference Advisory Committee on Evidence Rules (AdCom), in 2021, acknowledged that “in a fair number of cases, the courts have found expert testimony admissible even though the proponent has not satisfied the Rule 702(b) and (d) requirements by a preponderance of the evidence.”[10] This frank acknowledgement led the AdCom to propose amending Rule 702, “to clarify and emphasize” that gatekeeping requires determining whether the proponent has demonstrated to the court “that it is more likely than not that the proffered testimony meets the admissibility requirements set forth in the rule.”[11] The Proposed Committee Note written in support of amending Rule 702 observed that “many courts have held that the critical questions of the sufficiency of an expert’s basis, and the application of the expert’s methodology, are questions of weight and not admissibility. These rulings are an incorrect application of Rules 702 and 104(a).”[12]
The proposed new Rule 702 is now law,[13] with its remedial clarification that the proponent of expert witness opinion must show the court that the opinion is sufficiently supported by facts or data,[14] that the opinion is “the product of reliable principles and methods,”[15] and that the opinion “reflects a reliable application of the principles and methods to the facts of the case.”[16] The Rule prohibits deferring the evaluation of sufficiency of support or reliability of application of method to the trier of fact; there is no statutory support for suggesting that these inquires always or usually go to “weight and not admissibility,” or that there is a presumption of admissibility.
We may not have reached the Age of Aquarius, but the days of “easy admissibility” should be confined to the dustbin of legal history. Rule 702 is quickly approaching its 50th birthday, with the last 30 years witnessing the implementation of the promise and potential of an epistemic standard of trustworthiness for expert witness opinion testimony. Rule 702, in its present form, should go a long way towards putting validity questions squarely before the court under Rule 702. Nullius in verba[17] has been the motto of the Royal Society since 1660; it should now guide expert witness practice in federal court going forward.
[1] Pub. L. 93–595, §1, Jan. 2, 1975, 88 Stat. 1937 (emphasis added).
[2] Notes of Advisory Committee on Proposed Rules (1975) (emphasis added).
[3] See Charles T. McCormick, Handbook of the Law of Evidence 28-29, 363 (1954) (“Any relevant conclusions which are supported by a qualified expert witness should be received unless there are other reasons for exclusion.”)
[4] Frye v. United States, 293 F. 1013, 1014 (D.C. Cir. 1923).
[5] Daubert v. Merrell Dow Pharm., Inc., 509 U.S. 579 (1993).
[6] 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).
[7] See notes 5, 6, supra.
[8] John H. Mansfield, “An Embarrassing Episode in the History of the Law of Evidence,” 34 Seton Hall L. Rev. 77, 77 (2003); see also John H. Mansfield, “Scientific Evidence Under Daubert,” 28 St. Mary’s L.J. 1, 23 (1996). Professor Mansfield was the John H. Watson, Jr., Professor of Law, at the Harvard Law School. Many epithets were thrown in the heat of battle to establish meaningful controls over expert witness testimony. See, e.g., Kenneth Chesebro, “Galileo’s Retort: Peter Huber’s Junk Scholarship,” 42 Am. Univ. L. Rev. 1637 (1993). Mr. Chesebro was counsel of record for plaintiffs-appellants in Daubert, well before he became a convicted racketeer in Georgia.
[9] David Bernstein & Eric Lasker, “Defending Daubert: It’s Time to Amend Federal Rules of Evidence 702,” 57 Wm. & Mary L Rev. 1 (2015).
[10] Report of AdCom (May 15, 2021), at https://www.uscourts.gov/rules-policies/archives/committee-reports/advisory-committee-evidence-rules-may-2021. See also AdCom, Minutes of Meeting at 4 (Nov. 13, 2020) (“[F]ederal cases . . . revealed a pervasive problem with courts discussing expert admissibility requirements as matters of weight.”)], at https://www.uscourts.gov/rules-policies/archives/meeting-minutes/advisory-committee-evidence-rules-november-2020.
[11] Proposed Committee Note, Summary of Proposed New and Amended Federal Rules of Procedure (Oct. 19, 2022), at https://www.uscourts.gov/sites/default/files/2022_scotus_package_0.pdf
[12] Id. (emphasis added).
[13] In April 2023, Chief Justice Roberts transmitted the proposed Rule 702, to Congress, under the Rules Enabling Act, and highlighted that the amendment “shall take effect on December 1, 2023, and shall govern in all proceedings thereafter commenced and, insofar as just and practicable all proceedings then pending.” S. Ct. Order, at 3 (Apr. 24, 2023), https://www.supremecourt.gov/orders/courtorders/frev23_5468.pdf; S.Ct. Transmittal Package (Apr. 24, 2023), < https://www.uscourts.gov/sites/default/files/2022_scotus_package_0.pdf>.
[14] Rule 702(b).
[15] Rule 702(c).
[16] Rule 702(d).
[17] Take no one’s word for it.
