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Will My Expert Witness Appear Biased?



| With contributions from Christina Marinakis, JD, PsyD, Former IMS Strategy & Jury Consulting Advisor

The usefulness of any witness depends largely on their credibility with the jury. This is especially true for expert witnesses whose testimony is often pitted against that of an opposing counsel’s expert. In these instances, each expert’s credibility may determine which of their contradicting conclusions jurors choose to adopt. It is therefore perfectly reasonable that our clients sometimes ask, “Will my expert appear biased?”

First of all, jurors tend to be skeptical of any paid expert and, many times, if there are paid experts on both sides, jurors have told us they “canceled each other out.” Why? Jurors tell us that because a witness has been paid by a party, they appear to have a dog in the fight. In our post-trial interviews, jurors often say they “just wanted to hear from an independent expert.”

In our adversarial judicial system, we all know that is just wishful thinking. While you may never be able to undo the stigma of hanging your case on witnesses who are being paid to be there, there are ways of presenting an expert witness so that they appear less biased than their counterpart. Indeed, jurors don’t perceive all experts as “hired guns.”

Our experience interviewing jurors post-trial shows that many paid experts are taken seriously, and their opinions can hold important weight with the jury. So, what factors cause an expert to lose credibility with a group of jurors? Although there are many genres of experts, the following findings apply to most (if not all) experts who are likely to testify on behalf of your client at trial:

Factors That Influence an Expert’s Credibility

1. How much does your expert get paid?

Be mindful of how much the vast majority of jurors actually make for a living—or worse, how much they are being paid for their jury service. Many jurors are hard-working folks who earn hourly wages or modest salaries, especially when compared to your experts. When jurors hear that an expert is making $7,500 for their time to testify on that single day, that amount may equate to two- or three-month’s salary for your jurors. Jurors may surmise that, at such a rate, your expert would say anything to help your client.

One common tactic for minimizing this effect is to emphasize that the witness is being paid “for their time” as opposed to “for their testimony.” Your jury consultant may be able to suggest other ways to curtail the inherent bias that jurors are likely to perceive as a result of your witness’s hefty pay day.

2. For whom does the expert testify?

Another factor that makes jurors cringe is when they hear that an expert has only ever testified for one side or the other. The more a witness can show a mixed resume, the better. If a witness has testified for both plaintiffs and defendants in cases—even in different genres of litigation—they are less likely to come across as a zealot or as an expert on your payroll.

While this is often unavoidable when an expert’s findings or opinions always favor one side’s point of view, there are ways of conveying this caveat to the jury. For example, if true, the expert may want to explain that they will testify on behalf of any party who chooses to retain them, but, as of yet, they have never been approached by a plaintiff’s attorney, or even better, they have furnished reports or opinions to plaintiffs and the offer to testify at trial has been rejected).

It is always especially beneficial to point out when an expert’s research and publications pre-date their experiences as an expert witness—an indication that the expert’s findings were motivated by science, medicine, etc., as opposed to litigation. In instances where an expert is providing an opinion with regard to a particular plaintiff’s situation, it may be helpful to show that the expert furnished an independent evaluation of the case before agreeing to testify on behalf of your client and, if true, that they have rendered unfavorable opinions for your side on past cases, adding credence to their testimony in this case.

3. How arrogant is your expert?

An arrogant witness may project an impression that they are inconvenienced by having to testify, that they feel superior to the jurors and others in the courtroom, and that the case cannot be won without their testimony. These kinds of witnesses are often not self-aware and are insensitive to how they are perceived by others. They tend either to talk down to the jury or forget their audience altogether and lecture as if they were speaking to their colleagues or graduate students.

As a result, an arrogant witness fails to connect with a jury, and jurors are less likely to believe that an arrogant expert has approached the research and evidence with an open mind or evaluated the case fairly to arrive at their conclusions.

All of these factors can combine to make an incredible witness.

Although a pompous witness may be resistant to witness preparation with a jury consultant, an effective preparation can help them relate their wealth of knowledge to the jurors through thematic storytelling and engaging teaching techniques. Rather than submerging in technical or scientific details that are likely to alienate the jury, an effective—and credible—expert can simplify the science and become a humble teacher that your jury comes to trust.


Because expert witnesses do charge for their time and testimony, attorneys will have to deal with the fact that jurors are predisposed to perceive their experts as biased. Nevertheless, there are a number of ways to minimize this perception so that the question is not whether your witness will appear biased, but whether they will appear less biased than your opponent’s experts, and whether your witness can appear credible despite these biases.

Preparation for both the examining attorney and the witness with an experienced consultant is likely to address many of these concerns and develop methods for improving your witnesses’ overall credibility.

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