Mental Capacity as a Concept in Negligence: Against an Insanity Defence

A defendant's 'insanity' will not excuse his or her negligence. According to corrective justice theory, if A injures B, then A should compensate B - that A's actions may be attributable to a mental illness is therefore immaterial. Some tort scholars argue the law should excuse insane defendants from liability because they lack the mental capacity to commit negligence. 'Capacity' therefore lies at the core of the case for insanity defence. This article argues that 'capacity' fails as a framework concept for the insanity defence. It is poorly defined, fails to map onto the structural features of negligence and poses significant evidential challenges. It also has a spurious relationship with insanity. This paper prefers the status quo and concludes that the case for excusing the insane from negligence liability is conceptually flawed and normatively unconvincing.