Dressed to Kill (1980)
Michael Caine plays the part of a psychiatrist to a woman who is murdered early in the film. He is initially reluctant to help the police. The detective assigned to the murder seems happy to do nothing, leaving the investigation to a prostitute who witnessed the murder and the son of the deceased. I loved 'Dressed to Kill' - it is one of the quintessential thrillers of the 1980s and is a great suspense movie reminiscent of Alfred Hitchcock.