The body of Charlie Avouris was found slumped on a blood-flecked sofa in a cottage at Mumbil, 75km south-east of Dubbo, in the first week of July 1996.

A post mortem examination found the 30-year-old had been shot in the head with a small calibre bullet "on or around July 1".

Dubbo-based Detective Sergeant Scott Baker confirmed a number of suspects had been identified.

"One lives in the central west of NSW," he told the Daily Liberal.

"Another is located on the Central Coast. Good progress has been made and a number of lines of inquiry are continuing.

"We will be endeavouring to finish our investigation in 2016."

Detective Baker said investigators believe they know "who was responsible for the murder and who pulled the trigger".

"Several people are believed to have been present when the weapon was fired," he said.

"Police are convinced that Mr Avouris knew his killers."

Detective Baker said he was "unable to go into detail" about the actual murder.

He said the alleged killers had not been put before a court and the murder had not been the subject of a coronial inquiry.

"We still need small pieces of information to complete the puzzle so that evidence can go before the court," Detective Baker said.

"There are people in the community with knowledge of what happened to Mr Avouris. They are hiding what they know for their own safety or to protect others.

"I can only repeat what police have been saying since the murder occurred - come forward for the sake of Mr Avouris and his family.

"His parents, siblings and daughter still live in the metropolitan area. They want to know what happened to their son, brother and father.

"All information will be treated with the strictest confidence. We are happy to protect identities and prepared to meet people covertly at a location of their choosing, if that is their wish."

Detective Baker said "mountains of information" about the Avouris murder had been provided by the public over the years and police searches had been carried out on a number of properties.

"The murder investigation is actively continuing. Police are still seeking information about Mr Avouris and his associates.

"People willing to provide assistance should call Crime Stoppers on 1800 333 000 or make direct contact with Dubbo police station on 6883 1599."

Detective Baker said Mr Avouris grew up in the Wellington area and moved to Mumbil a short time before the murder.

At the time of his death he was living at Railway Cottage on Nargoogal Road.

Mumbil locals described the murder victim as a devoted father who loved horses.

"Mr Avouris was a stockman well-known for breaking horses and doing odd jobs on farms around the area," Detective Baker said.

"He played football and was a bit of a larrikin. He is understood to have been looking at relocating from Mumbil prior to his death.

"We are unsure of the reason why Mr Avouris wanted to move away."

In recent years advanced forensic technology has been used to retest DNA evidence found at the murder scene.

Detective Baker said Strikeforce Burrendong investigators were still in contact with the Avouris family.

In 2011 Mr Avouris' sister, Peggy, spoke of their heartache in an attempt to prick the conscience of people who had concealed vital information about the shooting.

"Whoever has done this has destroyed us," she said.

"This could be you. This could be your family."

Ms Avouris told a media conference she thought something was wrong during her last conversation with her brother.

"But he said everything was fine and not to worry," she said.

Ms Avouris, her brother, Adam, mother Maria and father Dennis have suffered agonising sorrow.

The heartbroken family has spent part of each Christmas Day beside a grave in a cemetery for the past 19 years.

They need closure but Strikeforce Burrendong detectives know that won't be possible until an arrest is made.