Ten Commandments for Effective Expert Deposition Testimony

Nov 21, 2022 at 01:11 am by Staff

Brian Peter Brinig


By Brian Peter Brinig, J.D., C.P.A.


Physicians are frequently required to provide testimony in depositions or trials relating to cases in which they have had some involvement.  Generally, the doctor is appearing as an expert witness and it is critically important for him or her to understand the procedures, strategies and tactics of expert witness testimony.

The most important underlying consideration for expert witness testimony is a commitment to tell the truth, the whole truth, and nothing but the truth.  No strategy or tactic obviates the foundational underpinning of this commitment.  But given that litigation is an argument, opposing attorneys are frequently committed to disagreeing with the physician’s view of the underlying facts or resulting opinions.  Doctors who are testifying as experts should be aware of the strategies and tactics to protect their well-thought-out positions from attack by an opposing side of a litigation matter.  The physician is not an advocate for any side of a litigation proceeding, but she is an advocate for a competently derived opinion.

The first discovery proceeding a physician is likely to be brought into is a deposition.  A deposition upon oral examination is a pretrial discovery procedure used to obtain facts relevant to a litigation matter. The witness is asked questions under oath by an examining lawyer, usually in the informal setting of a conference room in an attorney’s office. The questions and answers are transcribed by a court reporter verbatim, and many times the deposition is videotaped by a certified videographer. Because of liberal discovery rules, almost any question can be asked during the deposition.

While the official purpose of a deposition is to obtain relevant facts, the practical purpose of an expert deposition is broader. Recognizing that litigation is an argument, the deposing lawyer’s objective is often to obtain any information, on the record, that can be used to advance an opposing side of the argument at issue. Such information could include information to discredit or disqualify the witness from testifying on an issue. It could also include statements of agreement to particular facts that benefit the opposing side, or concessions that the assumptions made by the expert are not perfectly supportable. Another purpose is impeachment of the witness: if testimony at trial is different from the deposition testimony, the witness can be impeached with the deposition transcript at trial. Finally, a deposition intends to solidify the totality of an expert’s opinions during discovery so the opposing side knows every opinion the expert will testify to at trial. This last purpose is critical for the expert to understand because failure to include an important opinion in the deposition testimony will likely lead to exclusion of the opinion at trial.

Generally, a deposition is a losing proposition for an expert. The expert witness will testify under oath about every aspect of her involvement in the case, including factual observations, and research and analysis leading to the expert’s opinion and conclusions. Because the deposing attorney is possibly trying to obtain any information that can be used to discredit, impeach, or disagree with the expert’s opinions, an expert’s deposition is a minefield full of traps that must be avoided. A sophisticated knowledge of the strategies and tactics of the deposing attorney is also helpful to the deponent’s ability to minimize the harm suffered by experts in deposition.

I propose the following “Ten commandments for effective expert depositions" taken from my treatise, Mastering the Art of Expert Witness Testimony (Amazon: Burlington Business Press, 2022).  A complete discussion of the expert's strategies in litigation is beyond the scope of this brief article, but these commandments should assist physicians in the most common litigation proceedings in which they may be involved.


  1. Tell the truth, but answer only the question asked. Do not volunteer information and avoid long, narrative answers. The more topics that you bring up in your answer, the more questions the examining lawyer will ask. The deposition is an opportunity for the opponent to obtain information; it is not the trial. 
  2. Think about the question before answering it. This will give you the time to formulate an appropriate response. It will also give your party’s lawyer time to analyze the question and interpose any objections. Remember that the examining lawyer will attempt to develop an informal, but rapid conversation to elicit from you as much information as possible. Watch out for an examiner who attempts to catch you off guard with a casual friendly manner or flattering questions.
  3. Do not answer a question unless you understand it. If a question is unclear, ask the examining lawyer to repeat or rephrase the question or have the court reporter read the question back.
  4. Do not guess or speculate. If you do not know the answer to the question, say so. If you are not sure, qualify your answer by saying “approximately” or a similar qualification. Beware of hypothetical questions. Before answering a hypothetical, make sure that all essential facts or assumptions are included. Remember that at trial, a portion of the deposition may be taken out of context and used to impeach you.
  5. Only bring notes, diagrams, books or other written material to the deposition if they are required by a subpoena or if you have been instructed by your party’s lawyer to bring them. If asked to testify regarding documents or other exhibits, take the time to review them carefully before answering questions about them. 
  6. Listen carefully to objections made by your party’s lawyer. The objection may be intended to alert you to a trick question or some other problem with the question. If your party’s lawyer instructs you not to answer a question, follow his instructions, even if the examining lawyer threatens you with court sanctions. (See recommendation for making a record earlier in the text.)
  7. Do not argue or become angry or hostile with the examining lawyer. Such a reaction will communicate to the examining lawyer a lack of confidence that will be exploited at trial. It may also alert the examining lawyer to weaknesses in your theories or conclusions. As a general proposition, work hard to maintain a calm, collected attitude during the deposition.
  8. Even if the questioner calls for a yes or no answer, ask to explain your answer briefly if a qualification or explanation is necessary. However, do not be concerned if your answer does not supply all information which would be required for a complete understanding of the topic. Your party’s lawyer will decide whether to obtain a more complete explanation during the deposition or at trial.
  9. Watch out for questions which involve absolute terms, such as “Have you identified all of the documents which you have reviewed?” or “Are there any other facts that you have relied upon?” If possible, provide a qualified answer in the event that you inadvertently failed to identify a pertinent document or fact.
  10. Do not memorize your answers in advance of the deposition. Provide a direct and factual response to the questions. 

As in life, it is easier to read and understand the Ten Commandments than it is to live by them, but at a minimum, you should review them before any deposition you are called to attend. I think that knowing the Ten Commandments is “Expert Witness 101,” and knowing how to apply them judiciously is “Expert Witness 401.” In short, you don’t have to rigidly apply every one of them every time in deposition. Use your judgment, and good luck in your next deposition.

Mr. Brinig is Adjunct Professor of Law at the University of San Diego School of Law. He is the author of Mastering the Art of Expert Witness Testimony and he has testified as an expert witness in 300 trials and 600 depositions as a forensic economist in the past forty years.  He is a CPA and non-practicing lawyer and Managing Director of CBIZ Forensic Consulting Group in San Diego.  His book is available on Amazon.

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