MEMBERS of the Western Region Unsolved Homicide Team will now resort to DNA samples in the pursuit of a result in the investigation of the murder of Penny Hill 20 years ago.
Police have now collected DNA from 140 men, including those in Dubbo on August 26, with another 80 to be swabbed at various locations.
Unsolved Homicide Team coordinator Detective Chief Inspector John Lehmann said at earliest the team led by Detective Sergeant Jason Darcy could hope to finish the swabs of the other men by the end of 2012.
"It all depends on people's availability," he said.
Detective Chief Inspector Lehmann said mass DNA testing wasn't used often to find the perpetrator of a crime.
"It really depends on the circumstances of the case and Coolah being a small town it is more feasible to do it," he said.
"We thought it was realistic and not impossible."
All but one man on the list to be tested has consented to a DNA test.
"We identified who we wanted to speak to and those people were tested in Dubbo and across NSW," Detective Chief Inspector Lehmann said.
"This type of thing is really a process of elimination."
The fresh forensic evidence was uncovered in a secret compartment earlier this year in the Black Stump Motel in Coolah.
A rifle butt and a used condom were in the compartment which police can date to the time of the murder of Miss Hill.
"It basically started off when the new evidence was found this year but it has ramped up since the inquest finished in July," Detective Chief Inspector Lehmann said.
An open finding was handed down at the second coronial inquest into the death of Miss Hill in early July this year.
It was a big social weekend in Coolah when Miss Hill died, with a golf tournament, tennis competition and rugby league game all major events in the town.
Miss Hill was 21-years-old when she was found unconscious with severe head and facial injuries near the town at about 8am on July 8, 1991.
She died as a result of her injuries less than two weeks later at Newcastle's John Hunter Hospital.
Miss Hill had just taken the job of nanny for Billy Thorpe and the Aztecs' drummer, Colin Baigent, and his ex-wife Barbara.
A NSW government reward of up to $100,000 for information leading to the conviction of the person responsible for the murder of Ms Hill remains in place.
Anyone who can assist detectives should contact Crime Stoppers on 1800 333 000.