Mens rea ascription, expertise and outcome effects: Professional judges surveyed

•The first paper to present empirical data regarding mens rea ascriptions of professional judges.•Intentionality ascriptions of professional judges manifest the Knobe effect.•Intentionality ascriptions of judges are also sensitive to severity of outcome. A coherent practice of mens rea (‘guilty mind’) ascription in criminal law presupposes a concept of mens rea which is insensitive to the moral valence of an action’s outcome. For instance, an assessment of whether an agent harmed another person intentionally should be unaffected by the severity of harm done. Ascriptions of intentionality made by laypeople, however, are subject to a strong outcome bias. As demonstrated by the Knobe effect, a knowingly incurred negative side effect is standardly judged intentional, whereas a positive side effect is not. We report the first empirical investigation into intentionality ascriptions made by professional judges, which finds (i) that professionals are sensitive to the moral valence of outcome type, and (ii) that the worse the outcome, the higher the propensity to ascribe intentionality. The data shows the intentionality ascriptions of professional judges to be inconsistent with the concept of mens rea supposedly at the foundation of criminal law.