Legal Professionals Use an Implicit Checklist to Assess Expert Witness Credibility

Abstract

In a court of law, some forms of evidence are too technical to interpret without the help of an expert witness. However, expert testimony sometimes leads to wrongful conviction. We used an online survey to quantitatively compare how legal professionals (n = 122) and lay people (n = 109) understood what makes an expert witness credible. Both groups rated the importance of 22 criteria describing a hypothetical expert either in positive terms (e.g., "…has peer reviewed publications…") or negative terms (e.g., "…not licensed or accredited…"). Nine criteria showed significant differences between groups, and for other criteria, there was agreement. Compared to lay people, legal professionals placed more importance on criteria such as domain expertise (knowledge in one's field), and ability to answer the legal question at hand. It appears that legal professionals have refined credibility assessments potentially due to their education, knowledge of policy and guidance, and first-hand experience.