The clue is the latest in a string of evidence relating to the horrific cold case that police have revealed this week ahead of today's 15th anniversary of Mrs Palasics' death.

Mrs Palasics and her husband Gregor were watching television when two men wearing balaclavas broke into their McKellar home on the night of November 6, 1999.

The men tied the elderly couple up with cable ties and viciously bashed them as they ransacked the house for two hours, stealing large amounts of cash and jewellery.

Mr Palasics freed himself and phoned for help.

His wife suffocated In her own blood and died at the scene.

More than a decade later, police are still hunting her killers.

But new forensic evidence unearthed using cutting-edge DNA testing has given members of ACT Policing's homicide squad fresh hope the men could soon be brought to justice.

Detectives working on Mrs Palasics' case will hold a phone-in between 8am and 10pm today and have urged anyone with information to make contact.

Callers who believe they know the owner of the shoe, or who have any details about the crime, can speak to the officers anonymously by phoning Crime Stoppers on 1800 333 000.

Police on Sunday revealed a "familial DNA" search had proved one of the couples' attackers was a "close family relative" to one of five young men who broke into Pitch and Putt at Phillip on May 16, 2010.

CCTV footage led them to believe the group was among a 200-strong crowd at an 18th birthday party at the nearby Slovenian-Australian Association earlier that night.

Crime Stoppers received an anonymous phone call on October 20 from a person who claimed to have information regarding the identity of one of the five men from that break-in, but the caller hung up mid-conversation.

Police had also suspected two previous burglaries at the couple's Red Hill home in 1997 and 1998 were linked to the fatal attack.

Hair from a balaclava Mrs Palasics pulled off her attacker's head in the second home invasion showed "conclusively" that at least one of the men involved in the 1998 burglary was present at her murder.

They also renewed their plea for anyone with information relating to a getaway car they believe one of offenders used in an earlier robbery at the Palasics' previous home in Red Hill on October 10, 1998.

A witness told police he saw a person drive off in a small 1980s light blue or silver sedan which was parked on Quiros Street about the time the intruders fled.

The car was described as having a loud muffler, ACT registration plates and could have had a faulty headlight.

Police released a partial facefit image of a man they believe was one of the attackers that night, as well as another image of a man seen walking his dog in the area at the time who they believe could have seen the offender flee.

The officer in charge of the investigation, detective Senior Constable Jarryd Dunbar, said a piece of information from a member of the public, no matter how insignificant it seemed, could be "the final piece of the puzzle".

"There are people out there that can end this right now by picking up the phone or walking into a police station and telling us who killed Irma.

"We still believe that someone in Canberra knows the identity of those responsible or has suspicions about their involvement."

Senior Constable Dunbar reminded Canberrans a $500,000 reward for information leading to a successful prosecution in the case "won't be around forever".

Mrs Palasics' grandson John Mikita told The Canberra Times earlier this week his gut feeling was that the offenders still lived in the community.

"The hardest thing for us to deal with is the fact there are people out there who know the people who have done this," he said.

"If the same thing happened to them, what would they expect of anyone else in the community? Ring and just give the information."

Information to Crime Stoppers, 1800 333 000 or act.crimestoppers.com.au.