The difference between Pennsylvania’s approach to judges and expert ‘gatekeeping’ and that under the Federal Rules of Evidence is stark. For the Commonwealth and its Frye jurisprudence, judges are told to ‘leave science to the scientists.’ The proscription is clear and far-reaching:
[T]rial courts may not question the merits of the expert’s scientific theories, techniques or conclusions, and it is no part of the trial court’s function to assess whether it considers those theories, techniques and/or conclusions to be accurate or reliable based upon the available facts and data…[T]he trial court’s role is strictly limited to determining whether “the expert’s methodology is generally accepted in the relevant field.” Pa.R.E. 702(c). The trial court…may not go further to attempt to determine whether it agrees with the expert’s application of those methodologies or whether the expert’s conclusions have sufficient factual support.
Walsh v. BASF Corp., 234 A.3d 446, 458 (Pa. 2020).
The federal court Daubert standard envisions a different kind of gatekeeping, one purportedly made even more stringent after the December, 2023 amendment to FRE 702. The change to that Rule requires the proponent of the expert testimony to prove to the Judge’s satisfaction that “it is more likely than not that… (c) the testimony is the product of reliable principles and methods; and (d) the expert’s opinion reflects a reliable application of the principles and methods to the facts of the case.”
That the language change was not cosmetic is made clear from the Evidence Rules Committee’s accompanying notes. First, “The Committee concluded that emphasizing the preponderance standard in Rule 702 specifically was made necessary by the courts that have failed to apply correctly the reliability requirements of that rule.” In other words, some judges were letting the jury sort out whether expert testimony met the initial reliability threshold.
The Committee noted a second concern warranting ‘policing’ before admitting expert testimony:
[E]ach expert opinion must stay within the bounds of what can be concluded from a reliable application of the expert’s basis and methodology. Judicial gatekeeping is essential because just as jurors may be unable, due to lack of specialized knowledge, to evaluate meaningfully the reliability of scientific and other methods underlying expert 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 reliably support.
This added emphasis came from the world of forensic [criminal] expert testimony where witnesses offered conclusions beyond what the science or discipline can reasonably conclude.
But has the change made a difference? To some courts and not others. A sampling showed some post-amendment cases omitting any reference to the change and, in at least one instance, lauding a relaxed approach to admissibility determinations. “The rejection of expert testimony is the exception rather than the rule, and the trial court’s role as gatekeeper is not intended to serve as a replacement for the adversary system.” Larson v. Davidson Trucking, Inc., 2024 U.S. Dist. LEXIS 228695, *6.
Other courts, if not previously committed to stringent gatekeeping, got the message. As one court wrote, “[t]he Advisory Committee on Evidence Rules proposed the changes in response to court decisions that admitted expert testimony too liberally. These amendments “reflect an intent to empower courts to take seriously their roles as gatekeepers of expert evidence.” In re Terrorist Attacks on September 11, 2001, 2024 U.S. Dist. LEXIS 225265, *6-7. That court went on to scrutinize the proffered expert testimony and deem some of it insufficiently grounded in a reliable methodology.
So, where you are may determine the rigor of 702 analysis. But lessons/directions also come from appellate decisions, and a recent Third Circuit OPINION is a strong reminder that judges need to take gatekeeping seriously. Reversing a decision admitting expert testimony, the Court of Appeals found that “The District Court’s process fell short of the rigor required by Daubert and Rule 702. The Court dispatched four Daubert motions in a single hearing that lasted just over an hour, with less than thirty minutes devoted to the combined discussion of Drs. Strange and Hopper.” Cohen v. Cohen, 2025 U.S. App. LEXIS 415, *7.
The Circuit demonstrated the level of scrutiny that is required and why the testimony here was unreliable. Accepting that “dissociative amnesia” might be a well-accepted phenomenon, it then rejected the analytical leap made by the expert in question:
dissociative amnesia is the “inability to remember important biographical information, auto[-]biographical information, usually of a stressful or traumatic nature that is inconsistent with ordinary forgetting.” App 1645-46. But general acceptance of dissociative amnesia does not establish the same with respect to the accuracy of recovered memories. For “if one argued that the inclusion of dissociative amnesia in [the DSM] demonstrated acceptance of repressed memory, it would be analogous to saying that by recognizing the diagnosis of ‘hoofed mammals,’ one was demonstrating the acceptance of unicorns.”
Id., 2025 U.S. App. LEXIS 415, *10. The Circuit Court went further, parsing the studies relied on by the expert and noting that the studies were decades old, few in number, and suffered from small sample sizes. Finally, the Court found no “fit” between the testimony and the facts of the case.
The takeaways are simple. At least some courts will be more rigorous in gatekeeping; counsel should be prepared for the same; and Cohen v. Cohen and In re Terrorist Attacks are suggested reading for what questions need to be answered if you are the proponent of expert testimony or what ground(s) may be available for challenge. Or maybe take your case to state court.