Daubert challenges are won or lost on methodology, not credentials. A witness can hold an impressive resume and still be excluded, because the standard asks whether the expert's method of reaching the opinion is reliable and properly applied to the facts of the case — not whether the expert is generally qualified in their field. Framing a challenge around methodology, rather than attacking the expert personally, is what tends to persuade a court.

This guide walks through the reliability factors courts typically apply, how to build the factual record needed to support a challenge, and how the motion itself is usually structured. It describes a widely used legal framework in general terms; it is an educational explainer, not legal advice, and standards vary by jurisdiction, including states that have not adopted the Daubert framework.

Courts applying the Daubert framework typically weigh several non-exclusive factors: whether the theory or technique has been tested, whether it has been subjected to peer review and publication, its known or potential error rate, the existence of standards controlling its application, and whether it is generally accepted in the relevant scientific or technical community. No single factor is dispositive, and courts have discretion to weigh them differently depending on the type of expertise at issue.

The court's gatekeeping role is distinct from the jury's role in weighing credibility. A successful challenge argues the opinion should never reach the jury at all because the methodology is unreliable — not merely that the jury should discount it, which is the argument made through cross-examination once an expert is already admitted.

A Daubert motion is rarely won on the papers alone; it is won by exposing methodological gaps in the expert's own deposition testimony first, then citing that testimony in the motion. Depose the expert specifically to test the reliability factors, not just the substance of the opinion.

Courts routinely deny Daubert motions that amount to ordinary disagreement with an expert's conclusions rather than an attack on the reliability of the method used to reach them. Arguments like 'the expert should have weighted this factor differently' or 'a different expert would have reached a different number' are generally weight arguments for cross-examination, not admissibility arguments.

A methodology challenge instead targets the reliability of the process itself: an untested technique, a method with no error rate ever established, an analysis that departs from how the expert's own field actually applies the method, or an unbridgeable analytical gap between the data relied on and the opinion reached. Keeping the motion focused on process, not conclusion, is what separates a serious Daubert motion from a motion that reads as strategic cross-examination filed early.

An effective motion states the reliability standard, identifies the specific opinion being challenged, and then walks through the deposition record showing exactly where the methodology fails one or more of the reliability factors — not a general attack on the expert's qualifications or a recitation of every factor without connecting each to the facts.

Not every methodological weakness rises to exclusion, and courts frequently admit expert testimony while leaving its ultimate weight to the jury through the traditional tools of cross-examination, contrary evidence, and careful jury instruction. Build the same methodological record developed for a Daubert motion into a cross-examination outline as a fallback, so the work is not wasted if the challenge is denied.