Daubert Motion Examples: Rule 702, Factors, and Hearings

A Daubert motion is a pretrial request asking the judge to keep an opposing party’s expert witness off the stand because the methods behind the expert’s opinions are not reliable enough to meet Federal Rule of Evidence 702. The motion targets methodology, not credentials or conclusions, and it forces the judge to decide whether the science or technical analysis holds up before the jury ever hears it. Because a key expert often carries an entire theory of liability, causation, or damages, a successful motion can end the case on the spot.

What Rule 702 Requires

Federal Rule of Evidence 702 controls whether expert testimony gets into evidence in federal court. Under the version amended effective December 1, 2023, the party offering the expert must show the judge that it is “more likely than not” that four things are true: the specialized knowledge will help the jury, the testimony rests on sufficient facts or data, it comes from reliable principles and methods, and the expert applied those methods reliably to the case.¹ The 2023 amendment made the preponderance burden explicit, and it sits squarely on the party sponsoring the expert.²

The Supreme Court’s 1993 decision in Daubert v. Merrell Dow Pharmaceuticals, Inc. gave the trial judge an active gatekeeping role under this rule, requiring a preliminary finding that the expert’s reasoning and methodology are valid and tied to the facts.³ That gatekeeping duty is not limited to scientists; in Kumho Tire Co. v. Carmichael, the Court applied the same reliability screening to engineers, accountants, and any other witness offering technical or specialized knowledge.⁴

The Four Daubert Factors

The Daubert opinion set out four factors judges use to test reliability. They are flexible rather than a rigid checklist, and their weight shifts with the type of expertise at issue. Nearly every Daubert motion turns on one or more of them:

Testability. Can the theory or technique be tested, and has it actually been tested? A method that produces no falsifiable predictions gives the judge nothing to evaluate.
Peer review and publication. Has the methodology been written up and reviewed by other qualified professionals? Publication signals that the relevant community has scrutinized the approach, though its absence is not automatically fatal for newer techniques.
Known error rate. Every measurement technique carries some margin of error. The court asks whether that rate is known and whether it is acceptable for the use the expert is making of it.
General acceptance. How widely is the method accepted in the relevant field? Broad acceptance is not a guarantee of reliability, but widespread rejection is a serious problem.

These factors trace directly to the Court’s reasoning that “scientific” in Rule 702 implies methods grounded in the scientific process, while “knowledge” implies conclusions drawn from facts rather than speculation.³ Failing one factor rarely dooms the testimony on its own, but it hands the opposing side real ammunition.

How to Build the Motion

A Daubert motion is a written pretrial filing, usually a motion in limine, asking the court to exclude specific expert testimony before trial begins. Complaining that the other side’s expert is wrong is not enough. The motion has to dismantle the methodology in a structured way.

Identify the expert and the exact testimony you are challenging. Name the expert, cite their report or deposition, and pinpoint the opinions at issue. Blanket objections rarely succeed.
Set out the legal framework. Cite Rule 702 and the Daubert trilogy (Daubert, Joiner, and Kumho Tire), plus any controlling circuit precedent on the type of expert involved.
Work through the factors. Walk the judge through each Daubert factor and show where the methodology falls short. If the expert used a proprietary model that has never been published, say so and prove it. If the technique has an unacceptably high error rate, present the data.
Attach the proof. Include the relevant excerpts from the expert’s deposition and report, plus scientific literature undercutting the method. A declaration from your own expert explaining why the method fails can be especially persuasive.
Argue prejudice. Explain how admitting the testimony would mislead the jury. Judges take seriously the risk that questionable opinions carry outsized weight when dressed up with expert credentials.

The goal is a concrete comparison between what the expert actually did and what Rule 702 demands. A strong motion points to specific analytical gaps, missing data, or logical leaps rather than resting on adjectives like “speculative.”

How to Defend Against One

If your expert is the target, you carry the Rule 702 burden. Your opposition brief has to answer each challenge directly.

Establish qualifications. Attach a detailed CV and highlight relevant education, training, publications, and hands-on experience. Qualifications alone will not defeat a methodology attack, but they frame why the expert’s analytical choices are reasonable.
Defend the methodology on its own terms. Show that the expert used the same intellectual rigor they would use outside litigation. Point to peer-reviewed literature supporting the approach, prior judicial acceptance of the same method, or testing and replication data.
Separate methodology from conclusions. Daubert gatekeeping scrutinizes the process, not the result. If the method is sound, disagreements about the ultimate opinion are for the jury to weigh through cross-examination.
Answer every factor the motion raises. If the moving party said the method was never peer-reviewed, identify the publications. If they challenged the error rate, put the numbers in front of the judge. Leaving a factor unaddressed reads as a concession.

Ask for a live hearing when the methodology is complex or unfamiliar. An expert who can walk the judge through their reasoning in person tends to fare better than one whose work is evaluated only on paper.

When the Motion Gets Filed

Federal courts have no single nationwide deadline for Daubert motions. Federal Rule of Civil Procedure 16 instead requires the judge to issue a scheduling order early in the case setting deadlines for pretrial motions, including challenges to expert testimony. Most courts set the Daubert deadline after expert discovery closes and well before trial. Some judges break out a specific “Daubert motion deadline”; others fold it into a general pretrial motion deadline. Rule 16 also contemplates that pretrial conferences will address admissibility rulings and limits on expert testimony, so judges expect these issues to be raised on time.⁵ Check the scheduling order in your case, and file early rather than late.

Will There Be a Hearing

After briefing, the judge may hold an evidentiary hearing under Federal Rule of Evidence 104(a), which gives the court authority to decide preliminary questions of admissibility.⁶ A Daubert hearing functions as a focused mini-trial on the reliability of the methodology.

A hearing is not required. Many judges decide the motion on the briefs when the written submissions cover the ground adequately. When methodology is complex or the stakes are high, a live hearing lets each side question the expert directly, and the judge can probe reasoning and evaluate credibility in a way that paper does not allow. The hearing happens outside the jury’s presence, and the normal rules of evidence are relaxed so the court can consider affidavits, deposition excerpts, and other materials that might not be admissible at trial.⁶

What Happens After the Ruling

A successful Daubert motion can effectively end a case. When the excluded expert was the only witness who could prove an essential element like causation or damages, the other side has nothing left on that issue, and the moving party typically follows with a motion for summary judgment. Empirical research on federal Daubert rulings shows that when a defendant successfully excludes a plaintiff’s expert, the plaintiff’s overall win rate drops sharply compared to cases where the challenge fails.

If the motion is denied, the expert testifies and the jury hears the opinion. Denial does not leave the challenging party without options. Cross-examination becomes the primary tool for attacking credibility, weight, and the weak points in the analysis. The Supreme Court in Daubert pointed to cross-examination, contrary evidence, and jury instructions on the burden of proof as the appropriate means of challenging testimony that clears the admissibility threshold.³

Appellate review of a Daubert ruling is deferential. In General Electric Co. v. Joiner, the Supreme Court held that trial judges get significant leeway under an abuse-of-discretion standard because they are closest to the evidence.⁷ The appellate court will not reweigh the Daubert factors; it reverses only when the decision falls outside the bounds of reason. Appeal usually has to wait for a final judgment, because admissibility rulings are interlocutory and rarely qualify for immediate review. In practice, the trial judge’s call sticks through trial, and the losing side preserves the issue for appeal after judgment.

State Courts May Use Frye Instead

The Daubert framework governs federal courts, and roughly two-thirds of states have adopted some version of it. A meaningful minority of states still follow the older Frye standard from the 1923 decision Frye v. United States. Under Frye, the question is simply whether the methodology has gained “general acceptance” in the relevant scientific community. There is no multi-factor reliability analysis.

The difference is practical. A novel but well-supported technique might survive a Daubert challenge in federal court because the judge can weigh testability and error rates favorably even without widespread adoption, yet be excluded in a Frye state for lack of broad acceptance. About a dozen states use hybrid approaches that blend elements of both standards or apply their own framework. If you are litigating in state court, identify which standard applies before you write a word of the motion; it shapes every argument in it.

1
Legal Information Institute. Federal Rules of Evidence Rule 702 – Testimony by Expert Witnesses
2
United States Courts. Federal Rules of Evidence Pamphlet – December 1, 2023
3
Cornell Law Institute. Daubert v. Merrell Dow Pharmaceuticals (92-102), 509 US 579 (1993)
4
Law.Cornell.Edu. Kumho Tire Co v Carmichael
5
Legal Information Institute (LII) at Cornell Law School. Rule 16 – Pretrial Conferences; Scheduling; Management
6
Legal Information Institute (Cornell Law School). Rule 104 – Preliminary Questions
7
Law.Cornell.Edu. General Electric Co v Joiner, 522 US 136 (1997)