Shirley Finn The Madam Murder

In 1975 Shirley Finn a brothel owner in Perth Australia is executed in her car after going to meet with a man who was supposed to help her out of a tax situation. There is a long standing belief that her death had much to do with the corruption in the WA police force at the time. Why was the young mother of three murdered that night and why with all the evidence is it still unsolved today?