6 Expert Witness Mistakes to Avoid

Your expert might be one of the most qualified people in his field. However, that alone won’t guarantee that he will be an asset to your case. The fact is that even the best experts are still human. The stress of deposition or trial can result in critical mistakes that might have been avoided with

ByJoseph O'Neill


Published on November 18, 2014


Updated onJune 22, 2020

Your expert might be one of the most qualified people in his field. However, that alone won’t guarantee that he will be an asset to your case. The fact is that even the best experts are still human. The stress of deposition or trial can result in critical mistakes that might have been avoided with proper coaching and preparation. We caught up with nine top litigators from around the country to see what they have learned. And what to look out for when dealing with experts.

1.) Failing to Understand (or Bring) all the Pertinent Literature

“The first thing that comes to mind for me is an expert who doesn’t bring files to court because they are too heavy, or he couldn’t travel with all of it. This makes it too easy for opposing counsel to suggest some material was intentionally left behind. Better to be safe and bring everything that might be needed, even if it is difficult. We have even had experts FedEx material in advance so they can have everything with them in the courtroom.”

Jeff Korek – Gersowitz, Libo & Korek

“If there are learned treatises, he should be familiar with those that support and contradict his position so that he can ably address them. In this regard, the lawyer can introduce another expert’s opinion with little cost and no cross examination through learned treatises. If any written material is used in the cross, the expert should insist on taking time to carefully review all of it.”

Blake Bailey – Bailey Law Firm

2.) Failing to Disclose Negative Information About Their Past

“While I certainly accept the responsibility of vetting my experts in advance of their deposition, I would appreciate it if they would give me the heads up about any professional sanctions or reprimands or unrelated criminal charges. Several years ago, our expert admitted during cross examination that he had a criminal conviction for solicitation of prostitution, which subsequently required us to withdraw him as an expert and retain a new expert.”

Cephus Richard – Johnson, Vorhees & Martucci

3.) Lecturing During Deposition

“Experts can believe depositions are not an adversary proceeding but rather a classroom lecture. I have frequently seen this when an expert’s primary responsibility is as an educator – whether it be medicine, engineering, or other technical professions. There are, of course, many opportunities where an expert can be highly effective in the courtroom to educate a jury, but cross examination is not the place to volunteer information. The ideal expert not only has to have a command of the subject but be able to convey their knowledge to the jury.”

Paul Hines – Gasiorek, Morgan, Greco & McCauley

4.) Arguing With the Cross Examiner

“The biggest mistake experts make on cross is arguing back at the cross-examiner, either in “explaining” their “yes” or “no” answer, or bypassing the question altogether. Arguing the point converts the witness from an expert into an advocate and, no matter how articulate they may be, it will undermine their credibility. The worst example I can recall is one of my own experts (who I have not retained since). He was too arrogant to make the necessary concessions, and argued back – unfortunately taking positions inconsistent with trial testimony he had given in another matter a few months earlier. My adversary had a transcript. It was ugly.”

John D. North – Greenbaum, Rowe, Smith & Davis

5.) Going Against Their Previous Opinion

“One of the biggest mistakes I have ever seen an expert make is “forgetting” that he has testified for the exact opposite side of an issue in an earlier case. An expert talking out of both sides of his/her mouth is a horrible thing to find out (for counsel) at the expert’s deposition.”

John Bahe – Bahe, Cook, Cantley & Nefzger

6.) Going Outside Their Area of Expertise

“It is imperative that experts do not go outside the field of their expertise. When they do, an astute cross examiner will invariably run them out on that limb and cut it off. Then, even though that limb was inconsequential or irrelevant to that expert’s core testimony, it will undermine his or her overall credibility, as well as the matters for which he or she does have expertise and valid opinions.”

George A. LaMarca – LaMarca Law Group

“A common mistake of some expert witnesses is to profess specific knowledge of their area of expertise, whether it is medicine, engineering, or a science, and only a general knowledge of the testimony in the case. This testimony can be the key to the expert’s opinions and why his or her point of view should be believed by the jury.”

John Hickey – Hickey Law Firm

“With opposing experts especially, I often hear them testify beyond their specialty or expertise. For example, a family physician who opines about the standard of care for a specialist, when the education, background and experience of the family physician does not support the qualifications or expertise to provide such standard of care opinions. When this happens, either the opposing party is vulnerable to a motion to exclude certain expert testimony, or the expert is vulnerable to a vigorous cross examination on the lack of his or her qualifications.”

N. Jean Schendel – Hunt, Suedhoff, Kalamaros

About the author

Joseph O'Neill

Joseph O'Neill

Joe has extensive experience in online journalism and technical writing across a range of legal topics, including personal injury, meidcal malpractice, mass torts, consumer litigation, commercial litigation, and more. Joe spent close to six years working at Expert Institute, finishing up his role here as Director of Marketing. He has considerable knowledge across an array of legal topics pertaining to expert witnesses. Currently, Joe servces as Owner and Demand Generation Consultant at LightSail Consulting.

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