The Daubert standard is the test federal courts use to decide whether an expert witness’s testimony is reliable enough for a jury to hear. It comes from the 1993 Supreme Court decision in Daubert v. Merrell Dow Pharmaceuticals and puts the trial judge in charge of vetting an expert’s methodology against a flexible, five-factor reliability check before that expert takes the stand.1Cornell Law Institute. Daubert v. Merrell Dow Pharmaceuticals (92-102), 509 U.S. 579 (1993) A majority of states have adopted some version of it. The rest still use an older test.
The Five Factors Judges Weigh
The Supreme Court laid out a flexible checklist, not a rigid formula. No single factor decides the question, and a judge doesn’t have to apply every factor in every case. These are the considerations that guide the analysis:2Cornell Law School Legal Information Institute (LII). Daubert Standard
- Testability. Can the expert’s theory or technique be tested, and has anyone actually tested it? A method that can’t be verified through observation or experiment raises immediate concerns.
- Peer review and publication. Has the method been published and scrutinized by other qualified researchers? Peer review doesn’t guarantee correctness, but it means the work has survived outside criticism.
- Known or potential error rate. How often does the technique produce wrong results? A method with a 0.3% false-identification rate looks very different from one with a 15% error rate.
- Standards controlling the technique. Are there established protocols governing how the method is applied? Consistent procedures reduce the risk that results depend on the individual practitioner rather than the underlying science.
- General acceptance. Is the theory or technique widely accepted in the relevant scientific community? This was the sole test under the earlier Frye standard. Under Daubert, it still matters but is no longer the only question.
A judge has wide discretion to emphasize or downplay particular factors depending on the kind of expertise involved. An epidemiologist and a tire-failure analyst present very different kinds of evidence, and the analysis reflects that.
The Judge as Gatekeeper
The most consequential piece of Daubert was assigning judges a gatekeeping role. Before any expert testimony reaches the jury, the trial judge conducts a preliminary review of the expert’s reasoning, methodology, and qualifications.2Cornell Law School Legal Information Institute (LII). Daubert Standard The judge isn’t deciding whether the expert’s conclusions are right. That remains the jury’s job. The judge decides whether the expert reached those conclusions through methods sound enough to be worth hearing.
That distinction matters. Before Daubert, questionable scientific testimony could reach a jury on the strength of the expert’s credentials alone. Gatekeeping is designed to filter unreliable methods before they can influence the outcome. When a judge excludes an expert, it often reshapes the entire case. In product liability, medical malpractice, and toxic tort litigation, the expert’s testimony is frequently the linchpin. Lose your expert, and you may not have enough evidence to survive summary judgment.
The 2023 Amendment to Rule 702
Federal Rule of Evidence 702 is the statutory foundation for expert testimony, and it was amended effective December 1, 2023. The current rule says a qualified expert may testify if “the proponent demonstrates to the court that it is more likely than not” that the testimony meets four requirements: the expert’s specialized knowledge will help the jury, the testimony rests on sufficient facts or data, it results from reliable principles and methods, and the expert has reliably applied those methods to the case’s facts.3United States Courts. Federal Rules of Evidence
The key change is the “more likely than not” language, which formally imposes a preponderance-of-the-evidence burden on the party offering the expert.4LII / Legal Information Institute. Rule 702 – Testimony by Expert Witnesses The clarification corrects a real problem. Many courts had treated questions about the strength of an expert’s basis and methodology as issues of “weight” for the jury rather than “admissibility” for the judge. The amendment makes clear the judge must find the reliability requirements are satisfied before the testimony goes to the jury at all. Daubert challenges now have more teeth than some courts had previously allowed.
Which Experts Fall Under Daubert
The original case involved scientific testimony, but the standard’s reach is broader. Rule 702 covers “scientific, technical, or other specialized knowledge,” and the Supreme Court confirmed in 1999 that Daubert applies to all of it.5Cornell Law Institute. Kumho Tire Co. v. Carmichael That case, Kumho Tire Co. v. Carmichael, involved a tire-failure analyst whose expertise came from hands-on experience rather than laboratory science. The gatekeeping obligation extends to engineers, accountants, vocational experts, and anyone else testifying based on specialized knowledge.
Not every expert relies on peer-reviewed studies or measurable error rates. An accident reconstructionist, a construction cost estimator, or a forensic accountant may base opinions largely on professional experience. Judges in those cases still apply the Daubert framework, but they have discretion to adjust which factors carry the most weight. Peer review might matter less for an experienced appraiser than for someone presenting DNA analysis. The core question is the same: is the expert’s reasoning reliable enough to help the jury, or is it unsupported speculation that would mislead them?
How a Daubert Challenge Works
To keep the other side’s expert off the stand, a party files a motion in limine, a pretrial request asking the judge to exclude specific evidence.6Legal Information Institute (LII) / Cornell Law School. Motion in Limine Motions targeting expert testimony are typically filed after discovery closes and heard before trial. The motion has to identify the specific expert, the opinions being challenged, and the reasons the methodology fails under the Daubert factors or Rule 702.
When the judge grants a hearing, both sides present evidence about the expert’s qualifications, methods, and the basis for the opinions. The expert usually testifies. Again, the hearing isn’t about whether the conclusions are correct; it’s about whether the path to those conclusions is methodologically sound. The judge then rules on whether the testimony is admissible in whole, in part, or not at all. A judge can also limit an expert to certain topics while excluding opinions that overreach the methodology.
Timing matters. Filing too late can result in the court denying the challenge outright regardless of its merit. Courts expect these motions early enough that a ruling won’t delay trial.
Where Daubert Doesn’t Apply: Frye and the State Split
Daubert governs federal court. State courts are a patchwork. Roughly 31 states and the District of Columbia have adopted some version of Daubert; the remaining states use the Frye standard, a modified version of Frye, or their own state-specific test.
Frye comes from a 1923 federal decision, Frye v. United States, and asks a single question: has the underlying method gained “general acceptance” in the relevant scientific community?7Legal Information Institute (LII) / Cornell Law School. Frye Standard The test is simple to state, and it produced real problems in practice. Novel but well-designed techniques could be locked out of court for years while the broader community caught up, while methods that had achieved acceptance through inertia rather than rigor sailed in. The practical difference matters for anyone in state-court litigation: an expert who clears the Daubert bar in federal court may face a different analysis in a state next door. The first question is always which admissibility standard governs in that jurisdiction.
The Daubert Trilogy
Lawyers and judges often refer to three Supreme Court decisions collectively as the “Daubert trilogy” because each built on the last:2Cornell Law School Legal Information Institute (LII). Daubert Standard
- Daubert v. Merrell Dow Pharmaceuticals (1993) replaced the Frye “general acceptance” test with a multi-factor reliability analysis and assigned judges the gatekeeping role.
- General Electric Co. v. Joiner (1997) established that appellate courts review a trial judge’s decision to admit or exclude expert testimony under the “abuse of discretion” standard, giving trial judges substantial leeway.8Legal Information Institute (LII) Supreme Court. General Electric Co. v. Joiner
- Kumho Tire Co. v. Carmichael (1999) extended the Daubert framework beyond scientific testimony to all forms of expert testimony, including experience-based and technical expertise.5Cornell Law Institute. Kumho Tire Co. v. Carmichael
Joiner is the one that gets overlooked, and it has real consequences. Because appellate courts apply the deferential abuse-of-discretion standard, trial judges have broad latitude. An appellate court won’t reverse a Daubert ruling just because it would have reached a different conclusion. It will reverse only if the trial judge’s decision was fundamentally unreasonable. That makes the trial-level hearing the most important battleground in any Daubert dispute.