Janet Lawrence told the WA Coroners Court on Thursday that when she worked at Zanzibar nightclub in the early 1970s, vice squad chief Bernie Johnson and his police colleagues Don Hancock and Vince Katich used to come in with Ms Finn and they'd sit at the "captain's table", which no one else was allowed to use.

When Mr Johnson once found Ms Lawrence and a Greek jeweller friend sitting there, he told them to "piss off".

"He's a nasty piece of work," she said to the man, who replied: "More nasty than you'll ever know. Just watch yourself."

The jeweller later told her he'd seen Mr Johnson wrap up a gun that was used to kill Ms Finn in newspaper, then place it in a bin outside the nightclub just before a garbage truck arrived.

"Bernie must have told him that was the gun that shot her," Ms Lawrence said.

She also told the court she received more information about 10 years ago regarding Mr Johnson, who once tipped a jug of beer over her head at the nightclub because she rejected his advances, and was stopped by her boss before he smashed it on her.

After she told a man that she'd worked there, he gave her a letter about the murder, asking her to get it into "the right hands".

The man, who was in his late 70s and very ill, said he knew the killer and had seen the gun, and wanted people to know but was scared.

Ms Lawrence said he told her he had managed a bank branch where the three detectives had set up accounts, not using their full names, in which they regularly deposited cash - possibly obtained from Ms Finn in exchange for police protection.

One of them showed him a gun, saying it was used to shoot the mother-of-three, Ms Lawrence testified.

She also said her father, who had been a policeman, had told her "the boys were demanding more money" than Ms Finn was prepared to pay so she threatened to expose them and "was silenced".

The court also heard from Ms Finn's ex-de facto George Webber, who claimed she'd told him Mr Johnson would "crawl into the back seat of her car ... like a mongrel dog" to take money at pre-arranged rendezvous.

Ms Lawrence said she had another connection with Ms Finn - using a duplex she owned next to her brothel to store belongings, which were destroyed when it was firebombed by police.

"They thought that Shirley was hiding something in there that was detrimental to them."

Ms Finn was shot four times in the head at point blank range while sitting in her car on the edge of Royal Perth Golf Club.

Australian Associated Press