THE stories are always similar: a crack addict is running through the streets, semi-naked and delirious, aggressively challenging anyone that gets in his way. It takes a dozen police officers to subdue and restrain him, at which point he collapses and dies.

Rare as these deaths are, more often than not police brutality is blamed and officers are taken to court, but researchers now think that such events are the result of a rare disorder called “excited delirium”.

Anecdotally, physicians use the term to describe a state in which a person becomes agitated and combative, with superhuman strength and skyrocketing body temperature. However, the American Medical Association does not recognise the disorder, which has led to claims that it does not exist and is merely an excuse used by police.