Scientific observation, experiment and discovery have been a driving force in human development. Without the proper application of the scientific method, virtually none of what humans take for granted as fundamental to modern human existence would be possible. Despite this undeniable truth, however, distrust in science and scientists is reaching new heights. A Pew Research Center survey conducted in the fall of 2023 reported the percentage of Americans saying that science has had a mostly positive effect on society had dropped by 16% since before the coronavirus outbreak, with trust in scientists likewise falling by 14%.
There are multiple drivers for this growing distrust, but the intersection between science and the law – and particularly how the law deals with science in the context of legal disputes – plays a prominent and often highly publicized role. Scientific evidence is centrally important to securing the fair and just resolution of litigation that touches on highly emotional issues ranging from the identification of criminal defendants, to questions about the causation of disease, to the proper use of chemicals and medications, to a proper understanding of complex financial issues. In the regulatory realm as well, the reliability of scientific decision-making is essential to all manner of informed policy decisions that touch on key aspects of how individuals interact with the government and their fellow citizens.
Expert testimony in litigation (and in regulatory disputes) can be subject to selection bias because of the nature of the adversarial and political context in which the issues are resolved. On any given scientific question, there often will be a wide range of opinions among even well-credentialed experts. In the scientific world, this wide range of opinions drives science forward as the process of experimentation, testing, and replication winnows out speculation and false beliefs (albeit sometimes slowly) and promotes valid scientific discoveries. In the legal arena, however, legal counsel and proponents of disputed claims will seek out expert opinions that support their positions, even if those opinions are untested or at the fringe of known scientific understanding. This disconnect between the normal scientific process and how science is used in the courtroom (and by some regulatory bodies) requires a separate, stringent analysis of expert opinions before they are admitted as relevant evidence for the resolution of such disputes.
In the context of civil and criminal litigation, federal and state courts have different standards for the admission of expert testimony to a jury. However, nearly all U.S. courts require judges to play some “gatekeeping” role before the expert testimony is admitted. Although the state law standards for admission vary by jurisdiction, they are all set up to protect jurors from being misled by unreliable or speculative hypotheses. Proponents of expert testimony bear the burden of establishing the admissibility of such expert testimony. Guidance from the U.S. Supreme Court in its Daubert trilogy in the 1990s and from the Federal Judicial Conference in its subsequent amendments to Federal Rule of Evidence 702 makes clear that this hurdle should be a high one, though many courts have resisted that guidance in the past.
On December 1, 2023, the Judicial Conference Committee on the Federal Rules of Evidence completed an eight-year review of judicial gatekeeping against unreliable expert testimony with the enactment of a new Rule 702.
As amended, Rule 702 reads as follows (new language underscored; deleted language stricken):
Rule 702. Testimony by Expert Witnesses
A witness who is qualified as an expert by knowledge, skill, experience, training, or education may testify in the form of an opinion or otherwise if the proponent demonstrates to the court that it is more likely than not that:
(a) the expert’s scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue;
(b) the testimony is based on sufficient facts or data;
(c) the testimony is the product of reliable principles and methods; and
(d) the expert has reliably applied expert’s opinion reflects a reliable application of the principles and methods to the facts of the case.
As explained in the Advisory Committee Note to the amendment and in the underlying deliberations set forth in committee handbooks, legal memoranda, and reports, the amendment was promulgated in response to the committee’s determination that many courts had been avoiding their gatekeeping responsibility, holding that questions going to the bases and application of the expert’s methodology went solely to the weight and not the admissibility of the proffered testimony. In a law review article explaining the Committee’s thinking, the chair of the Advisory Committee’s Subcommittee on Rule 702, noted that this error arose from judicial confusion over language in Daubert regarding the use of cross examination and contrary proof to challenge “shaky but admissible evidence.” Many courts had interpreted this language as liberalizing the admissibility standard and calling for use of the more lenient Rule 104(b) standard for admissibility, which is in fact in direct contravention of Daubert.
In amending Rule 702, the committee made clear that these courts had misunderstood the lesson of Daubert and the requirements set forth in existing Rule 702 and, in so doing, had failed in their important mission of keeping unreliable science out of the courtroom. The committee admonished the “many courts [that] 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 Rule 702 and 104(a).”
The committee also took aim at courts that admitted expert testimony that started with reliable facts and reliable methodologies but then stretched beyond what those facts and methodologies would reasonably support. This is often the most challenging step in a court’s gatekeeping function because it requires courts to closely scrutinize the analyses and reasoning by which an expert reaches his or her opinion. As the committee explained, however, “judicial gatekeeping is essential because just as jurors may be unable, due to a lack of specialized knowledge, to evaluate meaningfully the reliability of scientific and other methods underlying an expert’s opinion, jurors may also lack the specialized knowledge to determine whether the conclusions of an expert go beyond what the expert’s basis and methodology may reasonably support.”
In amending Rule 702, the Committee steered the courts back onto the path of sound science. The amended Rule 702 provides courts and proponents of proper scientific methodology and reasoning with a powerful new weapon to keep unreliable science out of the courtroom and protect against the distortions that such evidence can wreak on the proper administration of justice. Equally important, the rule places one of the key institutions of our democracy more firmly in the camp of sound science, and, if faithfully applied, should put an end to (or, more realistically, at least minimize) the types of jackpot verdicts based upon scientific speculation that help seed the distrust in science that undermines society’s ability to confront the many serious scientific challenges that will shape our future on this planet.