Now aged 71, John Massey spent 43 years in prison for the fatal shooting of a bouncer in 1975; neuro-criminologist Adrian Raine analyses his brain, genes and hormones, looking for biological causes of his aggressive, risk-taking behaviour.

After 22 years behind bars, convicted murderer Paul Aldridge submits himself to a series of biological and psychological tests as the experts reveal how risk factors in his brain, hormones and early childhood may have influenced his behaviour.

Anthony Powell served over 21 years in prison for murder, convicted in 1993 of shooting a man with a sawn-off shotgun; seven years after release, he submits himself to scientific examinations to determine whether he had control over his actions.