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Questions to Ask the Expert Witness on Cross-Examination

Paloma Capanna, Attorney at Law

October 01, 2013


The goal on cross-examination of the opposing expert witness is not just to ask questions; it is to weaken credibility, reliability, and weight.

Many litigators engage in cross-examination with an expert witness.

Also note that even if an attorney is proficient in this approach, it may not be the most strategic one.

There are five key questions applicable to any expert witness and reasons why you should ask the opposing expert witness:

1. What materials did you review to form your opinion?

There are two goals in asking this question:

(a) To challenge whether the expert witness prepared using all available materials, whether supportive or contradictory to his theory of the case. (b) To find out if there were more materials available than was provided to you through discovery. Ideally, the response of the expert witness amounts to as much information in the same format as you were provided. This would put the two of you on an equal footing.

2. Did you conduct any research, investigation, or testing in person or through a third party?

There are differing views on whether an expert witness should or should not adopt approaches like an investigator, meaning going out to the scene of an accident, replicating lab test results, doing some Internet research, or going to public record archives.

You may be entitled to a turnover of this information at trial, if you asked the appropriate discovery question and the materials were not furnished.

There’s also a chance that the opposing counsel doesn’t know the answer to this question, which can be a cause of concern for the opposing party.

3. How many reports did you produce and when did you submit the reports to the counsel?

Rules are different from one jurisdiction to the next, but the question is worth asking.

If you weren’t supplied with an expert report, particularly one in an earlier draft, then demand to obtain it, before asking any further questions.

Even if you cannot get access to additional reports, you can gain a sense of the timeline for the work product between the expert witness and opposing counsel.

If that relationship is new, you can question preparation, and you may also have a clue that another expert witness was previously involved.

Don’t miss the opportunity to discover a previous expert that was once hired but is not the one sitting on the witness stand, because those materials can be a crucial for cross-examination.

4. Do you advertise your expert witness service and how many cases have you served as an expert witness?

Many lawyers rely on searching Lexis or Westlaw for information on an expert witness.

As with all litigation lawyers, there are a slim majority of cases that go to trial decisions and an even slimmer chance that become reported cases or appeals.

Judges and juries alike are wary of “professional expert witnesses,” who spend a majority of their time involved with litigation attorneys, especially those who advertise.

Fact-finders tend towards expert witnesses who are in the field or retired from the field.

That said, be careful it doesn’t backfire, because some are expert witnesses for altruistic reasons, others because they are in a niche, still others because they are research academicians and others because – well – they simply are the expert in the field.

5. Daubert Standard: Is your technique the standard or the generally accepted method in your area of expert disciple?

Daubert standard is a rule of evidence for the admissibility of expert witness testimony.

An expert’s testimony can be thrown out if it does not pass the Daubert Standard.

The testimony of an expert witness must be based on facts and scientific data. The Daubert standard is outlined in Rule 702.


A witness who is qualified as an expert by knowledge, skill, experience, training, or education may testify in the form of an opinion or otherwise if:

(a) The expert’s scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue; (b) The testimony is based on sufficient facts or data; (c) The testimony is the product of reliable principles and methods; and (d) The expert has reliably applied the principles and methods to the facts of the case.

As Amended Dec. 1, 2011

Each one of these questions can lead to many more questions. And there are a good number of questions you can ask, but these are five important ones that can be asked of every expert witness, under oath, and on the witness stand.

These questions can provide valuable insights about the fundamental approach of any expert witness, the development of their opinion, and their credibility as an expert.

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