Recently, I was running a mock trial exercise with three retired judges. Reviewing the testimony, one shared a skepticism toward the “hired-gun” engineers they had heard, and opined that what is “more important is the intuitive sense about the nature of this subject area.” The other two judges quickly nodded in agreement, becoming in that moment quite a bit like a jury. Experts are not automatically believed because they are experts. To be credible, they have to overcome a few hurdles, and probably the biggest hurdle is, “To be useful, you have to be better than my own intuitions.”

A well prepared and effective expert, of course, can get over that hurdle. But it requires good communication and, sometimes, requires prioritizing skills and traits differently than you might expect. The question of what makes an expert witness credible has garnered a fair amount of research. Much of this research, however, looks at mock jurors outside the context of an actual trial. In one recent study (Wilcox & NicDaeid, 2018), however, two legal studies scholars looked at that practical question using actual jurors who served on homicide cases in Maine involving forensic experts. Surveying and interviewing those former jurors, the researchers focus on how they saw and used expert witnesses, addressing the research question, “What factors influence how real jurors judge the credibility of forensic science expert witnesses?” The answer is that many factors matter, but it boils down succinctly to the title of this post. Be Experienced

When asked to define experts, jurors focused on a words like “knowledgeable” and “specialized.” In comparing all of the ways to measure that knowledge, one trait came to the fore: experience. More important than training, academic education, continuing education, and credentialing, was the simple factor of whether the expert had walked the walk.

Years of experience matter because it is believed to convey an ability to apply knowledge and not just possess it. As one juror noted, “I think there are some people who can get many certifications and take many courses and classes, but they can’t actually apply it and have never applied it. I think there are people who have developed significant experience in the subject matter from just seeing, doing, being around it.” Key to that experience is the ability to develop discernment and a reference point. As another juror wrote, “Highly qualified people do not necessarily have the vast experience to know what is average or extraordinary or unusual.” The trick for newer experts who have not yet amassed substantial experience is to emphasize the experience contained in gaining an education and gaining credentials, and to also be solid on the next two traits.

Be Confident

Based on the jurors surveyed, confidence and demeanor are the most important factors in determining expert credibility, and the most common reasons given for trusting an expert. These traits also dovetail with communication style, with an avoidance of technical language and a willingness to offer firm opinions being key to perceived confidence. As one juror explained, “You could tell the ones that were trying to just spin a line and the ones that were the honest ones and that were real sincere about their job and/or the ones that were trying to avoid answering.”

That confidence is most on display in cross-examination when the expert is being pressed to answer difficult questions. Another juror adds, “It does influence your perception of the person, how they come across, if they’re back tracking or they’re tripped up by the lawyer and try to answer it, instead of just saying ‘I’m not sure about this.’ Or if it sounds like a contrived answer then that kind of sways my thinking about what the [expert] is saying.”

Be Visual

The final expert trait, and perhaps the easiest to manipulate, is to show jurors rather than just telling them. The authors noted,  “Jurors were more likely to find expert witnesses credible when they used demonstrative aids such as charts.” In the interviews, jurors mentioned relying on posters, PowerPoint presentations, and even 360 degree immersive crime scenes.

The value in these tools is not just found in the substantive information they carry. They also work very well in putting the expert into a teacher’s role. “When the expert witness played more of an educator’s role and took the time to teach the jurors a little about the science and how they came to their conclusions,” the authors note, “the jurors appeared to be more engaged.” As one juror noted in an interview, the key is in “being able to bring it down to a level for other people to understand it, I think almost like teaching.”


Wilcox, A. M., & NicDaeid, N. (2018). Jurors’ perceptions of forensic science expert witnesses: Experience, qualifications, testimony style and credibility. Forensic Science International.
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