He’s a barbaric killer, guilty of the most terrible crime. He abducted and tortured an innocent 17-year-old girl, brutally raped her, then left her to die. Yet when James Martin O’Donnell stood trial at Exeter Crown Court he was acquitted. Twenty years later a chance DNA test makes it tragically dear that there has been a shocking miscarriage of justice. But the law of double jeopardy means...