Retired prison officer Bruce John Preston made a second attempt at bail in Brisbane Supreme Court today, with lawyers claiming the case against him was weak and he should be allowed to go home.

Karen Edwards, her boyfriend Timothy Thomson and their friend Gordon Twaddle were gunned down in the bush at Spear Creek, outside Mount Isa, in 1978 — just days into a motorbike road trip around Australia.

The case was reviewed last year by the Homicide Investigation Unit’s cold case team, leading to the arrest of the then-63-year-old.

The murders were also examined in a true crime podcast called Spear Creek, produced by The Courier-Mail.

Police will allege the three friends met Preston on the road between Alice Springs and Mount Isa in early October, 1978. Preston was on his own motorbike road trip, travelling home to Mount Isa from interstate.

They allege Preston befriended Karen, 23, Tim, 31, and Gordon, 21, on the road and visited them at the Lake Moondarra Caravan Park in his hometown on the night of October 4, borrowing his father’s Toyota LandCruiser.

They believe Preston, a motorbike enthusiast, returned the following morning in his father’s car to take the friends sightseeing, but instead lured them into the bush and killed them in order to steal Tim’s valuable bike.

The car was later seen back at the caravan park where a man was spotted dismantling the friends’ camp and driving away with their possessions.

The bodies of Karen, Tim and Gordon were discovered in bushland at Spear Creek on October 24. The court heard all three had been shot in the head with a .22 rifle.

Preston was discovered with Tim’s bike two weeks later and told police he’d found it abandoned on the side of the road. The court heard Preston had had the bike since the day of the murders. He was convicted of theft at the time after pleading guilty to the charge.

Preston’s lawyer, Russell Pearce, argued his client should get bail because new material handed over by prosecutors included a report where a police officer “eliminated” him from the investigation back in 1980.

But Justice Peter Davis said the opinion of one police officer decades earlier was “irrelevant”.

“The fact that there is a coronial investigation and in the course of that investigation, the police officer expresses opinions about his case is pretty irrelevant,” he said.

Mr Pearce went on to argue that police could not prove it was Preston who arrived in the LandCruiser to meet the friends, and so could not prove he was the killer.

He told the court Preston denies having ever met Karen, Tim or Gordon and has told police they did not cross paths on the road.

He said descriptions of a “bearded man” who arrived at the caravan park in the LandCruiser did not match his client.

“He’s an elderly man,” Mr Pearce said.

“He’s doing it tough in custody because he has to be held in isolation because of his past career.”

Justice Davis reserved his decision on whether to grant Preston bail.