The Daubert Standard: What Attorneys Need to Know Before Retaining an Expert

The Daubert standard is the test most American courts use to decide whether expert testimony is reliable enough for a jury to hear. Under it, the trial judge acts as a gatekeeper, evaluating whether an expert’s opinion rests on scientifically valid reasoning and methodology that properly applies to the facts of the case.

The standard takes its name from Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579 (1993), where the U.S. Supreme Court held that Federal Rule of Evidence 702 — not the older general-acceptance test from Frye — governs the admissibility of expert testimony in federal court. Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999), extended that gatekeeping role beyond scientific testimony to technical and other specialized knowledge. Today, the majority of states apply Daubert or a closely related standard, though the details vary meaningfully by jurisdiction.

The Five Daubert Factors

Daubert gave trial judges a flexible, non-exclusive list of factors for assessing whether an expert’s methodology is reliable:

1. Testability — Can the expert’s theory or technique be tested, and has it been? Opinions that can’t be falsified tend to draw the sharpest scrutiny.
2. Peer review and publication — Has the methodology been examined by others in the field? Publication isn’t required, but its absence invites questions.
3. Known or potential error rate — What’s the technique’s error rate, and does the expert acknowledge it? Precision claims without error data are a recurring soft spot.
4. Standards and controls — Do accepted standards govern the technique’s operation, and did the expert follow them in this case?
5. General acceptance — Is the methodology generally accepted in the relevant community? The old Frye test survives inside Daubert as one factor among several.

No single factor controls, and courts routinely emphasize that the inquiry is flexible. The consistent theme: the focus is on the expert’s methodology, not their conclusions — though as the Court later clarified in General Electric Co. v. Joiner, 522 U.S. 136 (1997), too great an analytical gap between the data and the opinion is itself grounds for exclusion.

Daubert Motions and Hearings: How Challenges Actually Unfold

A Daubert challenge typically arrives as a pretrial motion to exclude — often alongside or shortly after summary judgment briefing — arguing that the opposing expert’s opinions fail Rule 702’s reliability requirements. The court may rule on the papers or convene a Daubert hearing, where the expert’s qualifications, methods, and application of those methods to the case are examined directly, outside the jury’s presence.

Strong litigation teams treat the challenge as a predictable stage of the case rather than a surprise. They build the record early: the expert’s methodology is documented in the report, the factual basis is complete, and the expert has articulated — before deposition — how their approach satisfies each reliability requirement. The teams that struggle are usually the ones discovering at the hearing how their expert describes their own methods.

Daubert, Frye, and Everything In Between

Not every courtroom applies Daubert. A handful of states — including California, New York, Illinois, Pennsylvania, Washington, and Minnesota — still follow the Frye general-acceptance standard , and several others apply hybrid or homegrown tests that fit neither label. Which standard governs shapes everything from motion strategy to expert selection, and the answer depends entirely on where the case is filed. For the standard in each jurisdiction, with the controlling case or statute, see our interactive state-by-state reference .

The 2023 Amendment Raised the Stakes

Federal Rule of Evidence 702 was amended effective December 1, 2023, to make explicit what many courts had underenforced: the proponent must demonstrate to the court that each admissibility requirement is met by a preponderance of the evidence, and the expert’s opinion must reflect a reliable application of their methodology to the facts. The amendment was a course correction aimed at courts that had waved reliability questions through to “go to the weight, not admissibility.” Early returns suggest judges are engaging the gatekeeping role more actively — which means the quality of the expert, and the rigor of their methods, matter earlier in the case than ever.

What This Means for Expert Selection

The practical takeaway: the Daubert inquiry starts before the expert is retained. An expert whose methodology is documented, whose field credentials are current, and whose opinions have already survived challenges is a fundamentally different asset than one who has never been tested — and that history is knowable in advance.

It’s why challenge history is a standard part of vetting at Homestead Experts, alongside credential verification and confirmation of active practice. Every placement includes a direct conversation with the matched expert before you commit — the same conversation where you can hear, firsthand, how they explain their methodology. There are no upfront fees, and a dedicated case manager supports the engagement from search through testimony.

If a current matter needs an expert who can withstand the gatekeeper, tell us about the case .

Accuracy Note

All case citations verified against official records (U.S. Reports / Cornell LII / Justia): Daubert, 509 U.S. 579 (1993); Kumho Tire, 526 U.S. 137 (1999); Joiner, 522 U.S. 136 (1997); Rule 702 amendment effective Dec. 1, 2023. The Frye-state list matches the verified dataset behind the by-state interactive page.