Psychological insights for judging expertise and implications for adversarial legal contexts

Determining which experts to trust is essential for both routine and high-stakes decisions, yet evaluating expertise can be difficult. In this Review, we examine the cognitive processes that underpin genuine expertise and explore the disconnect between psychological insights into expertise and the practical methods used to evaluate it. In settings where expertise must be evaluated by laypeople, such as adversarial legal trials, evaluators face substantial challenges, including knowledge disparities that hinder analysis, communication barriers that impact the clear explanation of expert methods, and procedural constraints that limit the scrutiny of expert evidence. These challenges complicate the assessment of expert claims and contribute to wrongful convictions and unjust outcomes. We suggest that a distinction between ‘show-it’ and ‘know-it’ expert performances that differ in their visibility, measurability and immediacy can be used as a heuristic for identifying when evaluations of expertise require greater care and should incorporate a variety of diagnostic factors including foundational and applied validity. Finally, we highlight key knowledge gaps and propose promising directions for future research to improve evaluations of expertise in a range of contexts.