Abstract
It is well documented that people with moderate-to-severe traumatic brain injury (TBI) can undergo personality changes, including becoming more impulsive in terms of how they behave. Legal guidance and academic commentary support the view that impulsiveness can render someone decisionally incompetent as defined by English and Welsh law. However, impulsiveness is a trait found within the healthy population. Arguably, impulsiveness is also a trait that gives rise to behaviours that should normally be tolerated even when they cause harm to the person enacting the behaviours. The purpose of this paper is to show why both of these considerations present as significant challenges to the law in England and Wales.