It is a well-known fact amongst true crime enthusiasts that head injuries are disproportionately common in serial killers. Whether we’re talking Jerry Brudos, Richard Ramirez (who suffered two) or David “Son of Sam” Berkowitz (who suffered three!), it seems like most serial killers were hit on the head at some point in their life. Truth is, brain injuries are common in criminals, more than they are in the general population. But why is that? And do all brain injuries lead to criminal behaviour? Will your cousin Timmy, who dove into an empty swimming pool, kill his dog? As both a true crime fanatic and someone who happens to study the link between brain and behaviour, I’m going to attempt to provide brief answers to those questions (except for that last one, only time will tell – sorry).