Although forensic psychiatrists are often asked to comment on a defendant's capacity to form the necessary mens rea for their alleged offence, little has been written on how mental disorders map onto legal concepts of mens rea, particularly those of intention. In this article we explore legal concepts of mens rea and the relevance of mental disorders and alcohol intoxication. We briefly consider philosophical approaches to intentional action and a variety of common mental disorders. We conclude that despite the presence of significant psychopathology it is rare for mental disorders to cause a defendant to lack the ability to form mens rea. Experts should therefore be cautious about coming to the conclusion that they do lead to a lack of capacity to form mens rea and should make clear the limits of their expertise, given the difficulty of translating clinical mental states into legal concepts of liability.
