Queensland police have reopened the cold case of the 40-year-old Mount Isa Spear Creek murder mystery.
Investigators from the Cold Case Investigation Team, with the assistance of Mount Isa Criminal Investigation Branch, commenced a full review into the unsolved 40-year-old homicide investigation last year.
Detective Senior Sergeant Tara Kentwell of the Cold Case Investigation Team said investigators were confident the renewed focus could lead to a breakthrough in the case.
"Despite 40 years passing, we remain committed to solving this case, bringing those responsible to justice and ultimately providing closure to the victims' families," Detective Senior Sergeant Kentwell said.
"We have reviewed thousands of pieces of information provided to police over the years, however, today we are launching a fresh appeal to encourage new witnesses and those who have already spoken to police to make contact with us.
"We are urging anyone who may have seen the group travelling on their two distinct motorcycles through the Northern Territory and in the Mount Isa area in early October, 1978 to come forward.
"We are particularly interested in speaking with anyone who may have seen a male motorcyclist who befriended the group and joined them on their travels between Frewena and Mount Isa."
Karen, Tim and Gordon were last seen alive leaving the Moondarra Caravan Park in Mount Isa in a brown and white Toyota Landcruiser long wheel drive with a man on the morning of Thursday, October 5.
A $250,000 reward remains in place for information which leads to the apprehension and conviction of the person or persons responsible for their murders.
Detective Senior Sergeant Kentwell said the renewed investigative focus was no longer linking the triple homicide to other murders publicised at the time.
"While we are keeping an open mind, we are no longer focusing on links to the murder of John Tzelaidis who was found deceased near Karratha in Western Australia a few months earlier," she said.
On the night of October 24 1978, Stan Harris made a grisly discovery in the bush while taking his greyhounds for a stroll.
Mr Harris and his fiance Kirsten Streicher happened upon a decomposing body sprawled against a tree in a dry river bed at Spear Creek, 12km from Mount Isa.
Police arrived the next morning to discover another two bodies slain in the long grass.
They were Karen Edwards (23), Tim Thompson (31) and Gordon Twaddle (21).
All three had been shot in the head at close range by a .22 calibre rifle, and were stripped of identification - with their pockets turned inside out.
They were all clothed, and had been left in the open to decompose.
The trio booked into the Moondarra Caravan Park on October 4 and the next morning they were seen leaving the site in a two tone "brown and white station wagon driven by another man".
They had left their campsite intact with Karen's Alsatian tied to a tree. The next day the gear and dog were gone.
Karen, Gordon and Tim were never seen alive again.
Anyone with information on the murders should contact Crime Stoppers on 1800 333 000.
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