Deposing an Expert Witness – 6 Tips For Success

Joseph O'Neill

Written by
— Updated on June 22, 2020


Worried about deposing an opponent’s expert? Don’t be. With plenty of preparation and the right strategy you can flush out a weak expert well before your case goes to trial. We’ve rounded up some tips from top litigators and legal advisers around the country to help you make the right moves during this crucial phase of your case.

1.) Keep Your Audience In Mind


“As lawyers get good at deposing experts, it becomes easier to speak at their level and impeach their opinions based on data or exceptions. Your audience may be a judge, but it is more likely to be a jury. Either way, assume nothing and keep things extremely simple. Make the expert define words and use examples. I once tore up an expert I had deposed many times. As I used to practice defending the claims I now bring, I knew this expert and his weaknesses well. I had hired him. As I walked out, head held high, a young lawyer with my office said, “I didn’t understand any of that.” I had won the battle but lost the war if I wanted to use the transcript at trial. Keep it simple and at a high school level.”

 John M. PhillipsThe Law Office of John M. Phillips 

2.) Never Take Expertise For Granted


“In my experience, when deposing an expert witness, it is highly effective to inquire as to the basis of their testimony. For example, I have had members of law enforcement testify as an expert witness in regards to the breathalyzer device in DUI cases. Once I start to ask them about the basis of their expert opinion, their knowledge is limited to the owner’s manual of the machine. They do not know anything about the company that made the breathalyzer or where the company is getting their information”

Michael RehmThe Law Office of Michael Rehm

3.) Know Where the Expert Stands


“Learn everything you can about what an expert witness you are deposing has said on the subject at hand. If there is a book the expert has written or a media appearance in which the expert arrived at different conclusions with similar facts, you want to be able to impeach the experts testimony based on these contradictions. The trick is to use the experts own words to undermine his credibility and veracity as an expert.”

Matthew Reischer, Esq.  – Legal Analyst,

4.) Become an Expert Yourself


“Know the profession. Whether the witness is an expert in medicine, engineering, law or any other profession, there are standards…in medicine, it is called the standard of care, but every profession has standards which govern the expert in certain situations. For example, if you are deposing an electrical engineer about wire insulation in a building electrical line, you should find the codes that govern that. A good lawyer becomes a student and learns the profession so he/she can properly depose the expert. In some cases, you can hire an expert to review what the anticipated opinions are and help guide you through the deposition.”

G. Grant Dixon III Dixon Law Office

5.) Do Some Detective Work


“Do your research to see if the expert has been “qualified in court” as an expert on the “exact topic” he/she is claiming to be an expert on. If you find that he/she has rarely or never qualified as expert on the particular issue in your case, you can raise that in the deposition to illustrate that this testimony should not be considered by the jury. In one case that I handled, I was able to find out that on a prior occasion the expert had been suspended by the California Medical Board for incompetence. Of course, when I confronted the expert with that information it totally destroyed his credibility.”

Paul WallinWallin & Klarich 

6.) Examine the Expert’s Relationships


“During the deposition, find out all you can about how the expert became retained by your adversary and the expert’s prior relationship with the adversary or the other party. You might find some interesting information.

In a case I had, I pressed the expert about his connection to the party for whom he was serving as an expert, and it turns out they were first cousins. The plaintiff, and his counsel, had hired plaintiff’s own cousin to be their expert. Obviously this completely undermined the expert’s credibility and objectivity, to the point it was laughable. Although this was an extreme and strange case, more often you might learn important and helpful information such as how many times this expert has been used by that law firm in previous cases. If the law firm routinely uses that expert, it could show some bias and that he/she is merely a “hired gun” for that law firm.”

James HuntSlater, Tenaglia, Fritz & Hunt

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