Convicted murderers submit themselves to biological and psychological investigations to determine whether they truly had control over their actions. First up is 71-year-old John Massey, Britain's longest-serving murderer, who spent 43 years in prison for the fatal shooting of a nightclub bouncer in 1975. Neurocriminologist Professor Adrian Raine looks for biological causes of his aggressive, risk-taking and psychopathic behaviour, and forensic psychologist Dr Vicky Thakordas-Desai takes him back in time to his most painful childhood experiences.

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