Michael Barnes, the coroner for the state of Queensland, said the women were almost certainly victims of a gang known in the Brisbane area at the time for violence against women, The (Brisbane) Courier-Mail reported. But Barnes said only one individual, Wayne Robert Hilton, who died in 1986, had enough evidence against him to bring a case to trial.
The bodies of Lorraine Ruth Wilson and Wendy Joy Evans, both from the Sydney area, were found in 1974 in the bush west of Brisbane. Both had been bound.
Barnes, who presided over an inquest into the deaths, said the killings would probably have involved more than one perpetrator.
"It is more likely Wendy Evans and Ruth Wilson tragically stumbled into this putrid pool of miscreants and were killed by them," he said.
The women were seen by witnesses who did not take any action, Barnes said.
"Their desperate cries for help that went unheeded are one of the most heartrending aspects of this terribly sad case," he said.
Barnes said the women were probably not raped because their bodies were fully clothed with their underwear in place when they were found.
Penny Allen, Wilson's cousin, had a message for the killers and for witnesses she said had "conveniently failed memories."
"You are all cowards, the whole lot of you, cowards," she said. "Murder itself is a ghastly, ghastly act and therefore your conscience must be filled with guilt, a taunted past and no pity."