December 1 marks an important and long-awaited change to Federal Rule of Evidence 702. The Rule, pertaining to the testimony of expert witnesses, has not received a substantive update since 2000, when it was amended in the wake of the Daubert decision. Now, more than 20 years later—and after years of study—the Rule has been amended to make two issues clear: (1) that the proponent of an expert’s testimony must establish the admissibility of that testimony by a preponderance of the evidence; and (2) that an expert’s opinion must reflect a reliable application of his or her methodology to the case. These changes reinforce the key gatekeeping role that courts play in ensuring that only helpful, reliable expert testimony is heard by the factfinder.

The Changes

The changes to Rule 702 are seemingly minor but offer important clarifications that should govern expert practice going forward. Below is the text of the Rule with additions shown in bold and deletions stricken through:

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’s opinion reflects a reliable application of the principles and methods to the facts of the case.

The Committee notes, as always, are a valuable resource for understanding and applying the amendments. The first change makes clear that the proponent of an expert’s testimony must establish its admissibility under Rule 702, subsections (a) through (d), by a preponderance of the evidence. As the Committee observes, “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).” The amendment is intended to address these incorrect interpretations. That said, as the Committee also cautions, even with the amendment some challenges to expert testimony will still go to weight rather than admissibility. For instance, if a court finds that a proponent has established the admissibility of an expert’s opinion under the preponderance standard, a challenge that the expert has “not read every single study that exists will raise a question of weight and not admissibility.”

The second change “emphasize[s] that each expert opinion must stay within the bounds of what can be concluded from a reliable application of the expert’s basis and methodology.” The Committee identified this change as particularly relevant to forensic experts, who “should avoid assertions of absolute or one hundred percent certainty—or to a reasonable degree of scientific certainty—if the methodology is subjective and thus potentially subject to error.” When faced with forensic evidence, the Committee recommends that courts inquire into the known or potential error rate of the methodology. The amendment is not intended to bar expert testimony that is stated with a specified degree of certainty that is consistent with substantive legal principles.

Finally, although not directly reflected in the text of the amendments, the Committee’s advisory note clarifies that the “expert’s knowledge [must] ‘help’ the trier of fact to understand the evidence or to determine a fact in issue.” It is not appropriate, as some courts have done, to apply a potentially stricter standard requiring that the testimony “appreciably help” the factfinder.

The Impact

What do these changes mean for expert practice going forward, including in class actions? As a result of the amendment, we expect courts to have a renewed and refreshed focus on expert admissibility issues and their crucial gatekeeping role. Even before the amendments came into force, some courts were already focusing on the coming changes. See, e.g., Sardis v. Overhead Door Corp., 10 F.4th 268, 284 (4th Cir. 2021) (“Consistent with that existing law––and in accordance with the Committee’s pending rule––we confirm once again the indispensable nature of district courts’ Rule 702 gatekeeping function in all cases in which expert testimony is challenged on relevance and/or reliability grounds.”).

We have three preliminary predictions for how these amendments will affect expert practice.

First, litigants should be prepared for increased attention by courts to threshold expert admissibility questions and be ready to establish (or challenge) that admissibility under the preponderance standard. The amended Rule makes clear that questions like “Is the expert’s testimony based on sufficient facts or data?” and “Is the expert’s testimony the product of reliable principles and methods?” must be evaluated by the court as part of its gatekeeping function. These are threshold admissibility issues, not issues of weight.

Second, practitioners should carefully consider the application of an expert’s methodology to the facts and evidence in the case. The expert’s opinions must reflect a reliable application of that methodology and should not overstate the certainty with which the expert’s opinion can appropriately be expressed.

Third, litigants should be aware that case law that incorrectly applied the prior version of Rule 702 (such as those holding that threshold questions about an expert’s methodology went to weight, not admissibility) should have no precedential value going forward. Litigants should be on the lookout for situations where their opponents rely on outdated authority to defend the admissibility of their experts’ testimony and be prepared to raise the issue to the court.