It was 1972 when Michael Hayes picked up Mary Costa, a prostitute, drove her out in the desert, robbed her and then murdered her - bringing his then pregnant girlfriend Diana Walker to help him dump her body by the side of the road. Walker was a battered girlfriend (later wife) and Hayes threatened to kill her if she said anything. The case ran cold until 1976 when Walker (who had escaped Hayes and now had a new boyfriend) was urged by said new boyfriend to go to the police about the murder. The police were initially hesitant to believe her as they thought she had got the details surrounding the case from the newspaper and was trying to frame Hayes as a scorned ex girlfriend. However, she took them to the very spot Costa was killed without any prompt from the detectives - proving she was telling the truth. However, the detectives couldn't get the funding to go and visit Hayes and interview him in 1976 and so the case went cold once again. Flash forward to 2010 and Costa's 45 year old son Jimmy Stellflug (he was 7 at the time his mother was killed) contacted the police department to ask if he could have the ring she had died wearing as a memento of his mother if they were not going to investigate his mother's murder. This request prompted the case to be reopened again and this time detectives were able to visit Hayes, who was living in a completely different place with another new wife (he had had a string of battered wives over the years) 40 years after he murdered Costa and interview and charge him with her murder. Walker and many other of Hayes' ex wives who he had threatened by saying he'd 'killed a girl in the desert' testified against him. The defence tried to argue that Walker and the other ex wives had concocted the lie to scorn Hayes but this was deemed to be too elaborate. Hayes was found guilty of murder and charged with Costa's murder in 2015 - 43 years after she died. He was sentenced to life in prison with the chance of parole in 7 years (which was the law at the time he killed Costa) but Costa's son vows to make sure he dies in prison.