Cross-Examining Expert Witnesses in Missouri Cases

Expert witnesses occupy a unique position in Missouri litigation. Unlike fact witnesses who testify about what they saw or experienced, experts are permitted to offer opinions — about the cause of an accident, the extent of an injury, the standard of medical care, or the economic value of a life disrupted.

That privilege comes with scrutiny. The cross-examination of expert witnesses is one of the most demanding and consequential skills in trial advocacy. When done well, it exposes flawed reasoning, reveals hidden bias, and gives the jury reason to discount testimony that might otherwise carry decisive weight.

Why Expert Testimony Matters So Much

In Missouri personal injury cases, expert witnesses often determine the outcome. A biomechanical engineer explains how the collision forces caused the plaintiff's spinal injury. An economist projects lifetime earnings losses. A life care planner outlines decades of future medical needs. A defense medical examiner disputes the severity of the injuries.

Juries rely on expert testimony because these technical questions fall outside ordinary experience. Most jurors cannot independently assess whether a herniated disc at L4-L5 is consistent with a rear-end collision at 25 miles per hour. They depend on the experts to explain it.

This reliance makes cross-examination essential. If an expert's opinion goes unchallenged, the jury is likely to accept it. Effective cross-examination gives the jury permission to question what an expert has told them.

Challenging Qualifications

The first area of cross-examination targets the expert's qualifications — not to disqualify them, but to put their credentials in context.

An orthopedic surgeon who last performed surgery five years ago may be less persuasive than one who operates weekly. A biomechanical engineer who has never visited an actual crash site may be less credible than one who reconstructs accidents in the field. An economist who has never worked outside litigation consulting may carry less weight than one who advises businesses and government agencies.

These distinctions do not render the expert unqualified. But they help the jury calibrate how much weight to give the testimony. Cross-examination questions might include:

• How many years has it been since you last treated a patient with this condition?
• What percentage of your professional income comes from litigation consulting?
• Have you published peer-reviewed research on this specific topic?

The goal is not to embarrass the expert. It is to give the jury accurate information about the foundation supporting the opinion.

Probing Methodology

Expert opinions are only as reliable as the methods used to reach them. Missouri courts evaluate expert testimony under standards that require opinions to be based on sufficient facts, reliable principles, and sound application of those principles to the case.

Cross-examination probes each of these elements:

Sufficient facts. Did the expert review all relevant medical records, or only a subset provided by the retaining attorney? Did the expert examine the plaintiff, or rely entirely on paper records? Did the expert visit the accident scene?

An expert who opines that the plaintiff's injuries are pre-existing but who never reviewed imaging studies from before the accident has reached a conclusion on incomplete data. Cross-examination makes that gap visible.

Reliable principles. Does the expert's methodology reflect accepted practice in the field? If an accident reconstruction expert uses a simulation model, has that model been validated? If a medical expert applies a diagnostic framework, is it the framework used by the relevant specialty?

Sound application. Even valid methods can be misapplied. An economist who projects future lost wages but uses an incorrect salary baseline has applied a sound methodology incorrectly. A medical expert who diagnoses a condition without performing the standard diagnostic tests has not followed the protocol they would use in clinical practice.

Exposing Bias

Expert witnesses are compensated for their time, and there is nothing improper about that. But the extent and pattern of compensation can reveal bias that the jury should know about.

Effective cross-examination explores:

Financial relationship. How much is the expert being paid for this case? How much have they earned from litigation work over the past year? Over their career?

Pattern of testimony. Does the expert always testify for the same side? A defense medical examiner who has never found an injury to be causally related to an accident in 200 consecutive cases may have a perspective that favors the defense regardless of the facts.

Relationship with the retaining firm. Has the expert worked with this law firm or insurance company before? How many times? A long-standing financial relationship can suggest that the expert's continued income depends on delivering favorable opinions.

Selection of materials. Who chose which records the expert reviewed? If the retaining attorney provided only selected documents, the expert's opinion may reflect a curated version of the facts rather than the complete picture.

The Power of Concessions

Not every cross-examination question challenges the witness. Some of the most effective cross-examination involves obtaining concessions — getting the expert to agree with facts that support the cross-examiner's case.

Even a defense medical examiner will typically agree that the plaintiff was involved in a significant collision, that the plaintiff sought medical treatment, and that the plaintiff underwent surgery. These are undisputed facts. But hearing the opposing expert confirm them carries weight with the jury.

Similarly, a plaintiff's economist might concede on cross-examination that certain assumptions — the plaintiff's career trajectory, inflation rates, discount rates — involve uncertainty. These concessions do not destroy the expert's opinion, but they help the jury understand its limitations.

The art of cross-examination lies in knowing which concessions to pursue and which battles to avoid. Experienced attorneys choose their targets carefully, focusing on points that matter to the jury's ultimate decision.

Impeachment with Prior Testimony

Expert witnesses who testify frequently create a body of prior statements — deposition transcripts, published articles, prior trial testimony, and presentations at professional conferences. These materials provide powerful impeachment opportunities.

If a defense medical examiner testified in a prior case that the same type of injury is "commonly caused by motor vehicle collisions," that prior statement contradicts their current testimony that the plaintiff's injury is unrelated to the accident.

If an economist published an article advocating a particular discount rate but uses a different rate in this case, the inconsistency undermines their credibility.

Cross-examiners invest significant preparation time identifying these prior inconsistencies before trial. The impeachment itself takes only minutes, but its impact can reshape how the jury evaluates the entire testimony.

Preparing Your Own Experts for Cross-Examination

If you are a plaintiff in a Missouri personal injury case, your experts will face cross-examination too. Preparation is essential:

Review all materials. Ensure your expert has reviewed every relevant record, not just the ones favorable to your case. An expert who appears unfamiliar with a document on cross-examination loses credibility.

Anticipate challenging questions. Your attorney should identify the areas where the defense is most likely to attack and prepare your expert to handle those questions calmly and directly.

Practice concise answers. Experts who ramble or become argumentative on cross-examination hurt their own credibility. The best expert witnesses answer questions directly, acknowledge reasonable points, and maintain their core opinions without being combative.

Acknowledge limitations. Experts who refuse to acknowledge any uncertainty appear biased. Credible experts can say "that is possible but unlikely based on the evidence" without undermining their overall opinion.

FAQ

Can an expert witness be prevented from testifying?

Yes. Either side can file a motion to exclude expert testimony if it does not meet Missouri's reliability standards. The judge evaluates whether the expert's opinions are based on sufficient facts, reliable methods, and sound application. If the testimony fails these tests, the judge may exclude it entirely or limit its scope.

How many expert witnesses are typical in a personal injury case?

It depends on the complexity of the case. A straightforward car accident case might involve one or two experts per side — a treating physician and perhaps an economist. Complex cases involving catastrophic injuries might involve five or more experts, including medical specialists, biomechanical engineers, life care planners, economists, and accident reconstruction specialists.

Do expert witnesses always testify in person?

Not necessarily. Missouri courts increasingly permit expert testimony by video, particularly for experts who are located out of state or whose scheduling constraints make in-person appearances impractical. However, in-person testimony generally carries more impact with juries.

How can I tell if an expert witness is biased?

Look at the pattern: Does the expert always testify for one side? Do they earn a significant portion of their income from litigation work? Have they reached the same conclusion in every similar case? These patterns, while not conclusive proof of bias, suggest that the expert's perspective may not be fully objective.

What happens if an expert makes a mistake during testimony?

Mistakes during testimony — citing an incorrect fact, misremembering a detail from the medical records, or applying an incorrect formula — can be corrected on redirect examination by the attorney who called the expert. However, cross-examination may have already highlighted the error for the jury, and first impressions are difficult to undo.

For case referrals or co-counsel inquiries, contact Joseph Ott at joe@ott.law or (314) 794-6900.

This article is for informational purposes only and does not constitute legal advice. Every case is different. Contact OTT Law at (314) 794-6900 for a free consultation specific to your situation.