How bad does someone have to be to deserve to die? In California, the members of a jury who convict a first-degree murderer have to make that decision. Casey Cohen is a private investigator who works for the defence on such trials. His brief is to prepare a picture of the accused to put before the jury, presenting a positive image using personal testimony of friends and relatives. A Life on Trial retraces one of his most difficult cases; that of Richard Ford , a former Los Angeles police officer turned contract killer. The programme features interviews with some of the people Cohen tracked down to testify in favour of Ford, the jurors who had to decide his fate, and Ford himself.