Working as an Expert - Tips for Expert Witnesses

If you're new to expert witness practice, or even if you have some experience as an expert, following a few basic practices can help you have a better relationship with the lawyers who hire you, can make you a better and more effective expert when you testify at deposition or trial, and can help you avoid mistakes that could hurt your client's case.


Get a Written Contract

Expert witnesses sometimes report having difficulty collecting their fees, or have questions about their ethical obligation to continue to work on a case when the law firms that hire them fall behind on payments. Sometimes a law firm will refuse to pay a bill, insisting that the client is responsible for the expert's bill and that the client should be billed instead of the law firm.

By using a written retainer agreement as a standard business practice, an expert can reduce the chance of having problems getting paid.

  • Enter into a written agreement with the attorney, signed and dated by the attorney, specifying your rate of compensation.

  • Get a sufficient retainer for your services as you may find it difficult to collect fees later, particularly if the attorney who hires you either loses the case or obtains a settlement that is smaller than anticipated.

  • Your agreement with the attorney should specify that you may decline to perform additional services if the attorney has not paid your fees for prior services.

Credentials and Credibility

Protect your credibility

During your initial conference with the attorney, state that you will form an independent opinion based upon the facts, and that there is a possibility that your opinion will not support the client's case. If the attorney who has contacted you is looking for a "hired gun" who will make the facts fit the attorney's desired conclusion, you are better off declining the case and preserving your credibility.

Try to maintain balance

Try to maintain a balanced practice as a litigation consult and and expert witness by representing both plaintiffs and defendants. If you always represent the same side, even if you are very careful about the clients and cases you take you risk looking like a "hired gun".

Maintain a Complete Curriculum Vitae

Maintain a list of the articles that you have published and the cases in which you have testified. Keep copies of your publications and prior testimony for your clients to review. An attorney will need that information in order to prepare for litigation where you may be challenged with your own writings and testimony.

Changes of Position

If you no longer hold some of the positions you have taken in prior litigation or in past writings, let your client know. You do not want your client to be surprised when opposing counsel attempts to impeach you for allegedly contradicting yourself.

Prepare Before You Testify

Understand your role at a deposition, and how to testify effectively:

Know the legal issues

Speak with your client about the legal issues that will be involved in the case, and make sure that you are comfortable with the legal terminology for your case.

Only one person may speak at a time

Everything you say at a deposition and at trial is being transcribed. The court reporter cannot make a good record when people interrupt each other or talk at the same time.

Only answer the question that was asked

Ordinarily, after you have answered the specific question that you were asked, you will not want to volunteer any additional information.

Even if opposing counsel sits silently and seems to expect you to say more, don't fall into the trap of filling the silence. If opposing counsel wants more information, you will be asked a follow-up question.

Get used to silence even if it makes you uncomfortable. It is your job to answer questions, not to fill silence.

Think before you answer questions

Whether on direct examination or cross-examination, think before you speak. It is almost always better for there to be a short pause before you answer a question than for you to give a bad answer.

You will be asked hypothetical questions that may be unfair

Opposing counsel may ask you to assume facts, and explain how your opinion would change if those facts were true.

When answering the questions, do not assume that the facts stated by opposing counsel are actually true: the attorney may be trying to confuse you, to make you doubt your findings, or to lay a foundation for a theory of the case that is not in fact supported by the facts.

It is okay to answer, "I don't know"

When you don't know the answer, "I don't know" may be the best answer that you can give.

I once heard a toxicologist complain that he was asked how his findings in an injury case would be affected based upon a source of contamination that he learned about for the first time during his deposition. He was flustered, and testified that the contamination "could have a substantial effect" on his conclusions.

When he calmed down back at his office, and analyzed the new information, he found that the effect was in fact minimal. But it was too late for him to fix his testimony and his client lost confidence in his ability to testify. The case settled for less than it was worth and he had to fight his client to get paid.

Had he answered, "I don't know," or, "The analysis is complex, and I will have to perform a new set of calculations before I can answer that question," he would have avoided a costly mistake.

Do not overstate your client's position

An overstatement can potentially devastate your credibility.

Pay close attention to questions

Answer the question that is asked, and only that question. If you don't understand a question, ask for it to be repeated.

You cannot help your client by answering a question that you do not understand.

You were not hired to impress people

You were hired to persuade people, not necessarily to impress them.

While in an ideal world you will impress everybody with whom you have contact while working as an expert, your primary role as an expert is not to impress.

Sometimes an expert witness comes across as self-important or arrogant, potentially alienating the jury. If you must choose between looking impressive and being likable, it is normally more effective to be liked. You should think of yourself as an personable teacher, not as the ultimate arbiter of fact.

Be Careful With Terms of Art

Most professions use terms of art, words and phrases that have a different meaning within the profession than they might have in a different context. When a term of art means something other than what a layperson would understand the word or phrase to mean, it is important to explain its meaning.

Make sure that you understand the legal terms of art the lawyers and judge in your case may use, and make sure that the client law firm understands the terms of art that you may be using as you explain your case. Be alert for possible confusion, and be prepared to explain any terms of art that you use during testimony rather than creating a possible ambiguity or misunderstanding.

Try to make your testimony understandable

Try to avoid technical jargon, but do not be imprecise.

For example, if you are testifying about an "adhesive failure", you will not want to refer to the adhesive as "glue" without first making a clear record of the differences between an "adhesive" and "glue," and explaining that you are using the wrong term to make your testimony more understandable. Otherwise, you can expect opposing counsel to use your testimony against you, to argue that you don't know the difference between "glue" and an "adhesive."

Don't follow opposing counsel's lead, if he is leading you astray

Sometimes opposing counsel will ask questions that are designed to lead you into giving misleading or inaccurate testimony.

Staying with the adhesive failure example, when questioning you, opposing counsel might repeatedly refer to the adhesive as "glue" in the hope that you will follow his lead. The short-term goal is to trick you into believing he is unsophisticated about the scientific issues, and the long-term goal is to be able to argue that you don't know the difference between "glue" and an "adhesive."

If you make a record, early in the questioning, that the substance at issue is an "adhesive," and that you are assuming that the references to "glue" are in fact references to the adhesive, you will prevent the later abuse of your testimony.

Listen for "red flag" questions

If opposing counsel asks you a question that sounds like "legalese," it may be an effort to trick you into making a damaging concession.

  • If you know the legal issues and standards governing the litigation, you should be able to avoid this type of trap.
  • If you do not, make sure that you get clarification of the question before you answer.

When it is possible to be definite, be definite

If you always start an answer with "I believe" or "In my opinion," the effect may be to suggest that your opinions are imprecise and that it is perfectly reasonable for people to disagree with you.

Be careful about accepting the opponent's facts

During a deposition, opposing counsel is likely to ask you to agree with certain key facts.

You should discuss the facts with your client before the deposition, and understand what facts are disputed, such that neither of you are surprised during your testimony.

Make sure that you don't accidentally concede a fact that will damages your client's case.

Copyright © 2005 Aaron Larson, All rights reserved. No portion of this article may be reproduced without the express written permission of the copyright holder. If you use a quotation, excerpt or paraphrase of this article, except as otherwise authorized in writing by the author of the article you must cite this article as a source for your work and include a link back to the original article from any online materials that incorporate or are derived from the content of this article.

This article was last reviewed or amended on May 7, 2018.