In the thirty years since the Supreme Court decided Daubert v. Merrill Dow Pharmaceuticals, the use of scientific evidence in the courtroom has produced much confusion. Although the scientific literacy of the judiciary has advanced considerably, the proper application of Daubert principles to expert testimony remains inconsistent.

Federal Rule of Evidence 702 establishes the criteria for the admissibility of expert testimony. The Rule, however, has not been amended since 2000, three years after Daubert. With decades of post-Daubert experience to guide it, the Committee on Rules of Practice and Procedure has now unanimously proposed changes to Rule 702 that will likely go into effect in December 2023.

Last year, the Advisory Committee on Evidence Rules identified several significant problems with the application of Rule 702 in federal courts:

  • Many courts continue to view the factual basis and reliability of an expert’s methodology as going to the weight of the expert evidence, rather than its admissibility. This has permitted juries, at times, to decide cases based on unreliable expert testimony.
  • Courts have applied inconsistent burdens of proof when deciding challenges to expert testimony. Some courts have viewed admissibility as the rule and exclusion the exception. They have read a “presumption of admissibility” into the rule.
  • Courts have misunderstood and misapplied (or ignored) scientific concepts such as the falsifiability and error rate of an expert’s methodology. As a result, experts have been permitted to testify in absolutes and draw conclusions that go beyond what their methodology supports.

The proposed amendments to Rule 702 attempt to remedy these problems. These amendments, however, do not adopt new standards but are instead intended to clarify existing standards. The proposed amendments reinforce the court’s role as “gatekeeper” by clarifying:

  • The proponent of expert testimony must prove all the requirements of Rule 702 by a preponderance of the evidence.
  • The proponent of expert testimony must prove the expert’s opinions are, more likely than not, based upon sufficient information and the product of a reliably applied scientific methodology.

These amendments are intended to correct the common misconception that questions of reliability of methodology and proper application of the methodology to the facts go to the weight of an expert’s testimony. These are, in fact, issues the court must decide when determining whether an expert opinion is admissible. The amendments are also intended to remind courts that expert opinion testimony cannot exceed the bounds of what the data and the methodology can support.

It is unusual for the Federal Rules to be amended to tell courts to apply the rules as they already are. This may well prove effective. If the amendments lead to more consistent application of Rule 702, that will benefit all parties. However, until more explicit standards of admissibility for expert evidence are developed, scientific principles will continue to challenge judges and parties alike.