A former top detective who was spoken about with fear by witnesses at an inquest into the murder of Perth brothel madam Shirley Finn has died.

Bernie Johnson was the chief of Western Australia's Vice Squad when Ms Finn was shot four times in the head at point blank range in 1975.

The WA Police Union has offered condolences to the family of Mr Johnson, who was aged in his 80s, following his death.

The body of Ms Finn was found at Royal Perth Golf Course just two days before a tax hearing where she had been threatening to blow the whistle on illicit dealings by politicians, businessmen and police.

Despite two cold case reviews, the execution-style killing has never been solved.

Mr Johnson was placed at the scene of Ms Finn's murder on the night of her death.

Witness Philip Hooper told the court he heard four gunshots when parked near the golf course and had been threatened to keep quiet by Mr Johnson for years, with the detective once putting a gun to his head.

Former police officer James Boland also told the court he had heard rumours Mr Johnson had been one of the people Ms Finn had threatened to expose.

Questions about murder left unanswered

Ms Finn's daughter, Bridget Shewring, said she hoped anyone with information about her mother's death would now speak out.

The execution-style killing of Shirley Finn remains unsolved. ( Facebook: Bridget Shewring )

"I hope some truth can come out now," she said.

"A lot of people were too frightened to talk while he was still alive and I just hope they can come forward and tell the truth."

Mr Johnson denied having anything to do with Ms Finn's murder.

The former detective did not give evidence during the inquest hearings last year because he had dementia and was living in a nursing home.

The inquest into Ms Finn's killing is due to resume later this year.

Ms Finn was found shot dead in her car at Royal Perth Golf Course. ( Supplied )

AAP/ABC