In 1997, a man and a woman stopped at a public rest stop on the Hume Highway at Penrose, near Marulan, where they noticed a body submerged at the edge of the river.
Police found a man who had been decapitated.
A couple of weeks later police were told four fishermen found a shopping bag with a human head in it in Salt Pan Creek, Padstow, a month earlier.
Police retrieved the head and it was confirmed as a match of the remains in Penrose.
The man’s remains and other items were forensically examined by a forensic sculptor to create a plaster recreation of the man’s face.
It was displayed as part of a public appeal for information later in 1997.
Despite extensive efforts, the man has never been identified.
In 1999, an inquest by the NSW Coroner found the man had been strangled to death by a person or multiple people around February 20, 1997.
Fingerprint and DNA analysis have failed to identify the man.
Police have now created a new reconstruction of the man’s face to appeal to the public for his identity.
The $500,000 reward for information is hoped to lead to the man’s identity or those responsible for his murder.
Deputy Premier and Minister for Police Paul Toole said the modern technology that police use today may help to solve the murder.
“While this is a particularly gruesome crime that occurred decades ago, police believe their questions can still be answered by someone in our community,” Mr Toole said.
“I’d encourage anyone with even the smallest piece of information to reach out to police.”
Homicide Squad Commander, Detective Superintendent Danny Doherty, said the man had a distinct tattoo that may help to identify him.
“We have also issued a photo of a distinct letter ‘A’ style tattoo found on the man’s upper-right arm in the hope someone may recognise him,” Detective Superintendent Doherty said.
“He was murdered in a particularly gruesome fashion and his naked body was left in a river on the side of a highway, his head decapitated.”
Anyone with information is urged to contact Crime Stoppers on 1800 333 000.