Why Expert Witnesses Get Excluded Under FRE 702 — and How to Avoid It

Exclusion is not rare and it is not random. The 2023 amendment to Federal Rule of Evidence 702 sharpened the standard: the proponent must show, more likely than not, that the opinion rests on sufficient facts, reliable methods, and a reliable application of those methods to the facts of the case. Courts now police that more openly — and across non-medical fields, a large share of challenged opinions are excluded or partially excluded, most often for methodology.

The grounds courts actually cite

• Scope / qualification. The witness is qualified for part of the opinion but reaches beyond it. Exclusion is often partial — the overreaching piece is struck, gutting the opinion's force.
• Unreliable methodology. The method has an unknown or high error rate, was developed for litigation, skips a step the field requires, or can't be tested. This is the single most-cited reason.
• Fit. The method is fine in the abstract but doesn't connect to the facts of this case — the "analytical gap" between data and conclusion is too wide.
• Unverified assumptions. The opinion is built on a premise the expert took from counsel or a party without independently checking it. Disprove the premise, lose the opinion.

What keeps an opinion in

Tie every conclusion to a named, accepted method in your field, and be explicit about its limits and error rate. Stay inside your demonstrated qualifications — and say so out loud. Independently verify the facts you rely on, and document that you did. Close the analytical gap: show your work from data to conclusion, step by step, in language a judge can follow.

Find the gaps before opposing counsel does

The exclusion motion is written from your own deposition transcript. So the best defense is to run the attack on yourself first — have your report and your testimony stress-tested against each FRE 702 ground, then fix what's exposed before you're sworn in. That is preparation; rereading the report is not.

Questions? Contact us at [email protected]. This article is general information, not legal advice.