A man who went gay bashing at a park where another man was murdered concedes he should have told police a friend claimed responsibility even though he was a liar.

It was over three decades ago and a different man is on trial for murder.

Stanley Bruce Early, 77, has pleaded not guilty to murdering Raymond Keam in Alison Park at Randwick in Sydney's eastern suburbs.

He's accused of bashing the 43-year-old martial arts expert, either alone or in a group, because he suspected Mr Keam was homosexual.

Mark Stewart told the NSW Supreme Court he went to Alison Park several times, seeing men get chased "probably every time", and thrice participating himself.

"Just to scare them I suppose," Mr Stewart said on Tuesday.

He and his friends wanted men out of the park after a story circulated that "apparently a young boy had been assaulted by someone".

He told police weeks after Mr Keam's body was discovered in January 1987 he had begun frequenting the park the previous year to go "p**fter bashing".

None of the people doing so intended to kill or seriously injure anyone, he said on Tuesday.

"They were just trying to deter people from the park."

Before speaking to police in February 1987, Mr Stewart had a conversation when the murder was discussed.

"What you've recorded is that (your friend) says 'I've done it, I killed him,' and that's something he clearly said to you," Early's barrister Jeffrey Clarke said.

The person cannot be named as they were under 18 at the time.

Mr Stewart did not tell police because his friend "was a big mouth that lies," he said.

Mr Clarke questioned why he did not think it worth mentioning the claim.

"I should have," Mr Stewart said.

The "big mouth" also introduced Mr Stewart to an older man whom they called "Spider", which the jury has been told was Early's nickname.

Crown prosecutor Ken McKay SC read a police statement to the court from a since-deceased person who recalled Alison Park being an after-school meeting place for high school students.

One afternoon, they went to the nearby home of "a male person I later found out was nicknamed Spider" with some others, including the "big mouth".

"Spider" showed the students a black, 18-inch baton.

"And I think, but I'm not sure, that he told us he was 'bashing p**fs' in the park with it," the statement recorded.

Mr Keam's unsolved death was one of 88 killings between 1976 and 2000 recently reviewed by police probing potential gay-hate violence and allegations of prior inaction.

He identified as heterosexual, was divorced from one woman and in a de facto relationship with another, having a child with each.

Early went to Bundaberg for his brother's birthday the day Mr Keam's body was discovered in the park across from his house.

He told police he learned of the murder when he returned from Queensland five days later.

The case is circumstantial and Mr Clarke told the jury on the first day there is no evidence anyone saw Early have any contact with Mr Keam.

The trial continues on Wednesday.

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