Relatively guilty

A policeman with a caved-in skull, his young wife found clutching the blood-stained murder weapon; it all looks pretty open and shut until Robbie detects the faint whiff of a defence and closes in on a witness who might cast a precious doubt on proceedings. So why is it, the nearer he gets to the truth and a possible acquittal, that Robbie's murder client becomes more and more eager to opt for a l...