Daubert and FRE 702 Expert Exclusion in Medical Malpractice: Pressure-Test Your Expert Before the Defense Moves

By John Mahoney · June 2026 · 9 min read

In a medical malpractice case, your expert is the case. If the defense gets your causation or standard-of-care expert excluded under Daubert and Federal Rule of Evidence 702, you do not just lose an opinion — you usually lose an element you are required to prove. With no admissible expert on causation or breach, the defense’s motion for summary judgment becomes, for most plaintiffs, nearly certain to succeed. The exclusion order and the dismissal often arrive in the same news cycle.

That is what makes a 702 challenge the single highest-stakes chokepoint in med-mal litigation. And it is also the one most plaintiff attorneys prepare for too late — in response to the defense’s motion, rather than before it. This article is about flipping that timing: pressure-testing your own expert against the 702 reliability prongs before the defense does, while you still have time to shore up the opinion, supplement the report, or, in a hard case, decide it is not the right expert.

Disclaimer: This article is for informational purposes only and is not legal advice. Daubert standards, the text of FRE 702, and each jurisdiction’s gatekeeping practice vary and evolve. Many states apply their own expert-admissibility standard rather than the federal rule. Always verify the controlling standard and current rule text in your jurisdiction.

Why a Struck Expert Is Usually Fatal

Causation and standard of care in a medical malpractice case are, in nearly every jurisdiction, matters that must be established through qualified expert testimony — the questions are outside the common knowledge of a lay jury. That dependency is exactly what a 702 motion exploits. The defense does not have to win on the merits. It only has to convince the court that your expert’s opinion is unreliable or unsupported enough to keep from the jury.

If that motion succeeds on a required element, the practical result is a record with no admissible proof of breach or causation — and summary judgment for the defense follows close behind. Trial-bar commentators describe a successful causation strike as making defense summary judgment nearly certain, and that framing is not hyperbole: you cannot get to a jury on an element you can no longer prove. A late or weak response to the motion is not a recoverable position; it is the end of the case.

What the 2023 FRE 702 Amendment Changed

The reliability bar moved. Effective December 1, 2023, FRE 702 was amended to make explicit two things some courts had been applying loosely. First, the proponent of the expert must show admissibility is more likely than not — a preponderance standard the rule now states on its face. Second, the expert’s opinion must reflect a reliable application of the methodology to the facts of the case; the rule was revised to foreclose the practice of treating an overstated or under-supported conclusion as a mere question of weight for the jury.

The practical takeaway for plaintiffs: arguments that “goes to weight, not admissibility” are weaker than they were a few years ago. An opinion that outruns its own support — that states a conclusion the methodology does not actually reach — is now squarely a 702 admissibility problem the court is expected to police. Verify the current text and your circuit’s post-amendment case law before you rely on a pre-2023 mental model.

The Four Reliability Prongs — Pressure-Test Each One

The familiar Daubert reliability factors are not a rigid checklist, and courts treat them as flexible and non-exclusive. But they remain the lens through which most gatekeeping happens, and they map cleanly onto how the defense will frame its motion. Run your own expert through each prong as if you were writing the motion to exclude.

1. Methodology: is the opinion the product of a reliable method?

This is where most med-mal exclusions actually live. Ask whether the expert is applying an identifiable, repeatable methodology — differential diagnosis, accepted clinical criteria, the literature — or simply asserting a conclusion from authority. The dangerous pattern is the ipse dixit opinion: “in my experience, this caused the injury,” with no traceable method connecting the records to the conclusion. Demand that your expert articulate the steps. If you cannot diagram the path from the medical records to the causation opinion, neither can the jury, and the court may not let them try.

2. Peer review and publication: is the underlying science accepted in the literature?

You do not need a published study for every link in the chain, but the core scientific premises should be supportable in the peer-reviewed literature, not invented for the case. Identify the key premises your expert relies on — the natural history of the condition, the window in which intervention changes outcome, the mechanism of injury — and confirm each is grounded in citable medical literature. An opinion built on premises the defense can show are unsupported or contradicted by the literature is exposed.

3. Known or potential error rate: how often is the method wrong?

This prong matters most where the opinion rests on a test, a measurement, or a quantitative inference. If your expert relies on imaging interpretation, a clinical score, or a statistical inference about timing, be ready to address the known limits and error characteristics of that method. You will not always have a clean number, and courts apply this factor flexibly — but an expert who has never considered the error rate of the very tool the opinion turns on is an expert the defense will enjoy deposing.

4. General acceptance: is this how the relevant medical community actually reasons?

General acceptance is no longer the sole test, but it remains highly persuasive. The question is whether the expert’s approach reflects how practitioners in the relevant specialty actually evaluate this problem — or whether it is a litigation-driven theory the field would not recognize. A standard-of-care opinion that no comparable physician would endorse, or a causation theory at odds with the consensus of the specialty, is a target. Confirm your expert can point to mainstream specialty practice, guidelines, or consensus statements, not a position held only by retained experts.

The Self-Audit: Read Your Own Report as the Motion to Exclude

The most useful exercise is to draft, in your own head or on paper, the brief the defense will file against your expert — then close every gap it would exploit. A practical pre-emption pass:

• Find the unsupported leap. Locate the single sentence where the opinion moves from data to conclusion. Is the method that bridges that gap stated, or assumed? That sentence is the motion’s target.
• Match the expert to the defendant’s field. Qualification and specialty fit feed reliability and admissibility both. An expert opining outside their lane invites a challenge before the methodology is even reached. (The same specialty-matching analysis governs the certificate-of-merit requirement in many states — align them.)
• Reconcile the report with the records. A causation opinion that rests on a fact the chart does not actually support is the easiest exclusion there is. Confirm every factual predicate traces to a specific, page-cited record entry.
• Hunt for overstatement. Post-2023, an opinion stated more strongly than the method supports is an admissibility problem, not a weight problem. Tighten “to a reasonable degree of medical certainty” language so it matches what the analysis can actually carry.
• Stress-test in deposition prep. The questions that expose an opinion at a Daubert hearing are the same ones the defense asks at deposition. If your expert cannot defend the method under questioning in your office, they will not survive it under cross.

Done early, this is a fixable exercise: you can supplement the report, add literature, retain a better-matched expert, or narrow the opinion to what the method supports. Done after the motion is filed, your options collapse to arguing with a record you can no longer change.

Build the Causation Chain Before You Need to Defend It

A 702-resilient causation opinion is, at bottom, an explicit chain: this breach, leading to this physiological consequence, leading to this injury, each link supported by the record and the literature. Opinions get excluded where a link is implied rather than shown. Mapping that chain — and confirming each link has a record citation and a literature basis — is the work that turns a vulnerable opinion into a defensible one. Our Causation Chain Builder helps lay out and pressure-test those links so the gaps are visible to you before they are visible to the defense.

Bottom Line

A struck causation or standard-of-care expert is one of the few events in a med-mal case that is close to unrecoverable — lose the expert on a required element and defense summary judgment is nearly certain. The 2023 FRE 702 amendment raised the bar and shrank the “goes to weight” escape hatch, so an opinion that overstates its own support is now an admissibility problem you must fix, not argue around.

The defensible move is to run your expert through the methodology, peer-review, error-rate, and general-acceptance prongs yourself — early — and to read your own report as the motion to exclude. Verify the controlling standard in your jurisdiction, confirm every factual predicate traces to the record, and tighten the opinion to exactly what the method supports. The case should be decided on the medicine, not lost at the gate.

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