An inquest into the 1975 execution-style murder of Perth brothel madam Shirley Finn has heard allegations former vice squad chief Bernie Johnson made a "bedroom confession" to the killing.

Key points: A witness testified Bernie Johnson's ex-partner told him about the confession

A witness testified Bernie Johnson's ex-partner told him about the confession Shirley Finn was found murdered in her car at Royal Perth Golf Course in 1975

Shirley Finn was found murdered in her car at Royal Perth Golf Course in 1975 Mr Johnson died last year, but his ex-partner has been recalled to give evidence

After an eight-month break, the inquest resumed at the Perth Coroner's Court and heard from a witness who said Mr Johnson's ex-partner, Carolyn Langan, had told him about the murder confession during the late 1980s.

CSIRO scientist Craig Klauber said Ms Langan, who began working in administration at the CSIRO in Perth in 1986, came into his office one morning and said to him, "Bernie told me in bed last night that he had killed Shirley Finn."

Ms Finn was shot four times in the head, and her body was found slumped over the wheel of her white Dodge Phoenix at Royal Perth Golf Course on a June morning in 1975.

She was killed just two days before a tax hearing, where she had been threatening to blow the whistle on illicit dealings by high-profile politicians, businessmen and police.

Bernie Johnson has been linked to Ms Finn's murder by a number of witnesses. ( Supplied )

Dr Klauber told the court he had no knowledge about the murder or the brothel madam at the time.

But he said once Ms Langan explained the background, he found it "chilling".

He said Ms Langan, whom he considered a close friend, told him not to tell anyone else, and said he believed she had confided in him as a safety measure, in case anything were to happen to her.

Mr Johnson, who has been linked to Ms Finn's murder by a number of the more than 50 witnesses the inquest has already heard from, died in April last year.

Threats stopped me going to police: witness

Dr Klauber said that sometime later Ms Langan came into his office "pale and visibly upset", telling him Mr Johnson had threatened her with a gun to the face the night before.

"My advice then was she had to leave Bernie," he told the court.

"She was clearly very frightened at that stage.

"But she kept saying, 'Bernie won't hurt me, Bernie won't hurt me'."

When asked why he had not gone to the police, Dr Klauber said he felt he "was a witness too far removed from the events to be credible".

He also said he was later spoken to by Mr Johnson on two occasions in what he inferred as threats, and decided it was safest for him not to go to police.

Ms Finn was found slumped over the wheel of her car at the Royal Perth Golf Course. ( Supplied )

"I presumed, after Bernie's threats, if I did nothing and said nothing further I'd be OK," he said.

Ms Langan's lawyer, Louis Durand, told Dr Klauber his client had no recollection of any of the allegations and denied them all.

Police chief's ex-partner recalled to give evidence

It is not the first time the inquest has heard allegations of Ms Langan discussing Mr Johnson's alleged involvement in Ms Finn's murder.

Ms Finn had been threatening to blow the whistle on illicit dealings by public figures. ( Facebook: Bridget Shewring )

Last year, Ross Stone and Errol Stone gave second-hand accounts of what Gratton Stone — Ross's father and Errol's brother — had told them from when Ms Langan lived with him in the early 2000s.

Ms Langan denied those allegations as well.

But Dr Klauber said it was hearing Ms Langan's evidence in July, which he said was untruthful, that compelled him to come forward with what she had told him all those years ago.

"I don't understand what she's got to gain by not telling the truth," he said.

Ms Langan, who said she had been engaged to Mr Johnson and had dated him for about 15 years, has been recalled to give evidence to the inquest on Thursday.

Allegations of buried gold

The inquest also heard from Joan Wilson, who Dr Klauber said he understood was also involved with Mr Johnson at the same time Ms Langan was and while the detective was still married to his wife, Christine.

Dr Klauber said he had become close friends with Ms Wilson's daughter, Amanda Marzo, in 1989 after hiring her as his horse riding instructor.

He told the court he was invited to their home one night in December that year, when Ms Wilson asked him, as a scientist, what he knew of gold processing.

He said she went on to mention how $300,000 worth of gold was buried on a property belonging to Mr Johnson in Gidgegannup.

Ms Wilson denied the claims and told the court while she had been on a few dates with Mr Johnson, she did not know a Carolyn Langan and had never met Dr Klauber.

But counsel assisting the coroner, Toby Bishop, said Ms Wilson had told police during a phone call in August last year that she was "vaguely aware of Craig Klauber".