Britain's longest serving murderer, John Massey, submits himself to a ground-breaking biological and psychological investigation to determine whether he truly had control over his actions.

Aged 20, Paul Aldridge was convicted of murder by joint enterprise and sentenced to life in prison. Now Paul submits himself to a series of biological and psychological tests.

Anthony Powell served over 21 years in prison for murder. Now he submits himself to biological and psychological investigations to determine whether he had control over his actions.