What Factors Influence Jurors’ Opinions of Expert Witness Credibility?

Dani Alexis Ryskamp, J.D.

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— Updated on February 12, 2021

What Factors Influence Jurors’ Opinions of Expert Witness Credibility?

When many legal teams choose an expert witness, they do so with an eye to the credentials that will, hopefully, establish their witness as an expert in the eyes of the judge. The perceived credibility of your witness in the eyes of the jury has a significant impact on the outcome of the trial, and should be an equally key consideration in expert selection.

Expert Witness Credibility

Research on jurors’ perceptions of expert witness credibility has found that the following five factors play a major role in building the credibility of your chosen expert witness:


A 2009 study in The Journal of the American Academy of Psychiatry and the Law examined the link between expert witness confidence and juror perceptions of their credibility. The researchers defined “confidence” as “the degree of demonstrable self-assurance expert witnesses have in their general ability on the stand,” assuming that anxious behaviors arose from low self-assurance.

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The study found that increased confidence by the witness also increased jurors’ perceptions of a witnesses’s credibility—but only to a point. “Medium” confidence levels resulted in slightly higher credibility rankings than “high” confidence levels, although both groups scored better than the witnesses who appeared to have “low” confidence. Researchers also provided insight into ways to improve witness credibility, such as by working through courtroom procedure and detailing what to expect with your expert witnesses before.


A study published in The Journal of the American Academy of Psychiatry and the Law found that extraversion—as measured by expressiveness in face, movement, and voice—made expert witnesses more likeable to jurors. The effects of likeability on credibility, however, varied among jurors. Jurors who were extraverted themselves tended to find witnesses more credible if they liked the witnesses more, while jurors who were more introverted found expert witnesses equally credible whether they liked the witness or not.

Eye Contact

Moderated eye contact has long been considered a key factor in credibility, with endless studies and articles claiming that averting gaze is a sign of uncertainty, anxiety, or outright dishonesty. For certain expert witnesses, however, eye contact may have a significant impact.

A 2008 article in Criminology and Behavior tested eye contact and credibility using an excerpt from a trial transcript in which an expert gave testimony on whether a criminal defendant was likely to reoffend. Researchers found that the more eye contact the speaker made, the more likely the listeners were to rank the speaker as “credible” if the speaker was male. If the speaker was female, however, eye contact did not seem to matter. Researchers recommended that “male experts should maintain eye contact for maximum credibility.”

Witness Roles

In a 2013 presentation to the Annual Conference of the ABA Section of Litigation titled “Demeanor, Deception and Credibility in Witnesses,” Dr. Cynthia R. Cohen explained that jurors do not consider the credibility of any witness in a vacuum. Rather, they factor in the witness’s relationship to the case when determining credibility. Jurors may view a particular witness as credible—and a particular piece of information as more believable—depending on whether it comes from a friend, treating physician, or unconnected expert witnesses. As a result, lawyers and their teams should consider carefully which witness offers the best “credibility boost” for each fact.


The background of an expert witnesses plays a key role in having the witness certified as an expert. Unsurprisingly, it affects jurors’ perceptions of the witness’s “expert” status as well. In a 2003 study published in Law and Social Inquiry, researchers examined how jurors responded to information provided at trial about the witness’s background. Education and experience played a key role in establishing credibility: for example, one juror noted that he gave a particular doctor’s testimony more weight because he recognized the doctor’s medical school as one of the best in the country.

A lack of formal education or high-ranking experience did not automatically ruin an expert’s credibility to jurors, however. For example, one juror noted that while a testifying biomechanical engineer had a “hands-on” background, the juror identified with that as someone with little formal education himself, and was willing to take the engineer more seriously as a result. Often, a lack of formal degrees can be addressed in court by establishing the expert’s hands-on experience.

Considering these factors when choosing an expert witness can help you prepare a witness for trial more easily and bolster your witnesses’ credibility in the eyes of the jury.

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