Bruce John Preston, 63, has been charged with three counts of murder more than 40 years after his alleged victims' bodies were found at Spear Creek in outback Queensland.

Mr Preston, then an unemployed diesel mechanic, was a suspect early on in the investigation, having been convicted and fined for stealing one of the victim's motorcycles in 1978.

Mr Preston, who had since worked at the supermax Goulburn jail, had been awarded a commendation for brave conduct by the NSW commissioner of corrective services in 2002.

A former Mount Isa local, Mr Preston has been charged with the 1978 murders of Karen Edwards, 23, Tim Thomson, 31, and Gordon Twaddle, 21.

The trio were found slain in the long grass near Mount Isa in 1978, weeks after they were shot in the head at close range by a .22 calibre rifle and stripped of identification, with their pockets turned inside out.

Weeks after the bodies were discovered, Mr Preston was convicted and fined after he was caught driving one of the victim's motorcycles.

After stealing the bike, Mr Preston had it cleaned, the wheels changed and removed the pannier bags.

Once the police appeal went out about the missing motorcycle, he had been "too scared" to tell police he had it.

The then-23-year-old also owned a car similar to the one seen carrying the three travellers from a caravan park. It was the last time the trio were seen alive.

Detectives began speaking to Mr Preston, who now resides in Goulburn, after The North West Starpublished an anniversary feature into the case, producing fresh leads for homicide detectives.

Ms Edwards, Mr Thomson and Mr Twaddle were murdered less than a week into their outback motorcycle adventure.

Mr Thomson and Mr Twaddle had spent the months preceding their deaths working around Alice Springs.

As their time in the red centre was coming to an end, Ms Edwards, Mr Thomson's girlfriend, flew up to Alice Springs to meet the pair and embark on a motorcycle adventure to Mount Isa, and then on to the east coast.

On Monday, October 2, 1978, the trio farewelled Alice Springs and began the 1170-kilometre journey to Mount Isa, camping at various places along the way.

Ms Edwards and Mr Thomson rode on an "expensive" red 1977 BMW motorcycle with a home-made sidecar and Gordon rode a blue 1977 Suzuki with Victorian registration plates.

Police had said they were "particularly interested" in speaking with anyone who may have seen a male motorcyclist who befriended the group at the outback NT rest stop of Frewena and joined them on the final 500-kilometre stretch into Mount Isa.

On the Wednesday, Mr Twaddle, Ms Edwards and Mr Thomson checked into the Moondarra Caravan Park at Mount Isa.

Their new motorcycle enthusiast friend did not check in with them, but a man was seen socialising with them the night they arrived.

The next day, the trio were spotted leaving the caravan park with a man in a brown and white landcruiser.

Ms Edwards, Mr Thomson and Mr Twaddle were never seen alive again.

When the trio left with the man, the campsite was intact and Mr Thomson's dog, Tristie, was tied to a tree.

Later that day, a man in the same brown and white Landcruiser was spotted back at the caravan park calling out for the dog by name.

All of the trio's gear, except for the motorcycle sidecar, had been left at the Mount Isa dump.

Mount Isa man Stan Harris and his fiance, Kirsten Streicher, found their decomposing bodies about two weeks later at Spear Creek, 12 kilometres from Mount Isa.

Mr Thomson's red motorcycle was believed to have been driven around town by Mr Preston for a month after the murder.

"A two-toned brown and white Toyota Landcruiser and a number of firearms associated with the man's address were examined by forensic officers in 1978," Detective Senior Sergeant Tara Kentwell said last month.