Damage to certain parts of the frontal lobe can impair people’s ability to make rational decisions and judgements, leading to changes in how they interact with others. In some cases, it can cause them to do things that they would not otherwise do, and therefore some brain-damaged people cannot be held fully responsible for their actions.
Mobbs D et al. Law, responsibility and the brain. PLos Biol 2007;5(4):e103