Daubert and Frye, explained for the retaining attorney

Every expert opinion you offer will be tested against one of two frameworks. Which one applies is a question of forum, not of preference — and the answer changes what your expert's file has to contain before the disclosure deadline, not after a challenge lands.

Frye: general acceptance

Frye v. United States, 293 F. 1013 (D.C. Cir. 1923), asks one question: is the scientific principle or technique generally accepted in the relevant scientific community? The community is the gatekeeper. A sound but novel method can fail Frye simply because the field has not yet converged on it. New York, California (as the Kelly rule), and Illinois are the large Frye jurisdictions in this docket; see the state index.

Daubert: judicial gatekeeping on reliability

Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579 (1993), made the trial judge the gatekeeper and replaced the single acceptance question with a reliability inquiry: has the theory been tested, has it been peer-reviewed and published, what is its known error rate, are there standards controlling its application, and is it generally accepted? Kumho Tire extended the same inquiry to technical and experience-based testimony. The framework is codified in Federal Rule of Evidence 702, amended December 1, 2023 to state expressly that the proponent must show admissibility is more likely than not — a clarification aimed at courts that had treated the burden as lighter.

What this means for the file you build

Under Daubert, build the reliability record as you retain: the method's literature, the expert's application of it to your facts, and the data underneath both. Under Frye, build the acceptance record: the treatises, standards-body positions, and prior admissions that show the field already accepts the method. In both forums, the expert's own prior testimony and publications are part of the record the other side will read first — which is why our CV guide treats the testimony list as the most important page of the document.

Sources: Frye v. United States, 293 F. 1013 (D.C. Cir. 1923); Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579 (1993); Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999); Federal Rule of Evidence 702 (as amended Dec. 1, 2023). This guide is information about a directory's subject matter, not legal advice.