Genetics, accidents of birth or events in early childhood have left criminals' brains and bodies with measurable flaws predisposing them to committing assault, murder and other antisocial acts. .... Many offenders also have impairments in their autonomic nervous system, the system responsible for the edgy, nervous feeling that can come with emotional arousal. This leads to a fearless, risk-taking personality, perhaps to compensate for chronic under-arousal. Many convicted criminals, like the Unabomber, have slow heartbeats. It also gives them lower heart rates, which explains why heart rate is such a good predictor of criminal tendencies. The Unabomber, Ted Kaczynski, for example, had a resting heart rate of just 54 beats per minute, which put him in the bottom 3 per cent of the population.