That has been the most difficult part of his family's search for answers and justice, nearly two decades after two men in balaclavas viciously attacked his grandparents in their McKellar home.

"It's the distrust," Mr Mikita said. "The insecurity of living this on a daily basis."

Irma and Gregor Palasics were watching television when the men stormed their home the night of November 6, 1999.

Irma, 73, and Gregor, 74, were bound, gagged and savagely beaten before the men ransacked the house over two hours and fled with cash and jewellery.

Mr Palasics, battered and covered in blood, freed himself once the offenders left and called for help. His wife died at the scene.

Their attackers have evaded police capture.

New forensic tests that suggested a DNA link between the murder and a putt-putt business break-in prompted a fresh push for information in late 2014.

But police dismissed the connection between the two incidents less than a year later, leaving Mrs Palasics' family in limbo again.

Mr Mikita said this month's anniversary of his grandmother's death marked 18 years of "heartbreak, disappointment and losing trust in the people who are there to keep us safe in doing just that".

He used to feel his home town was "the safest place on earth" before the attack transformed his view of the city to a place "my grandparents can be murdered and the offenders get away without being caught".

"You have to rely on people coming forward and even with all the exposure, no-one's come forward to say anything. And that's the hardest part for us, just that distrust of other Canberrans."

Mr Mikita was concerned pressure on police resources, insufficient funding and frequent staff changes in the homicide team had lessened his family's chances of ever finding answers.

"I am afraid that if the priorities of the powers that be continue to under-fund or under-value the vital work needed to ensure those cold case families like ours have their investigations solved.

"When you research the statistics it's quite shocking to think that if things keep going on, it's only a matter of time before another family goes through what we have."

Australian Federal Police Association president Angela Smith said resourcing pressures could affect cold case investigations, but it was more likely no fresh evidence had emerged.

She said probing unsolved cases was "resource intensive" and police "resources are cut to the bone at the moment".

"The only way [police] would close a cold case is if they absolutely know the murderer is dead. They're never closed permanently.

"Police - it's an innate thing - we want to solve crimes, and we always have the family at the forefront of our minds."

An ACT Policing spokeswoman said all cold case investigations in the territory remained active. She said any new information police got would be "assessed and actioned appropriately".

"Police urge anyone with information, no matter how minor, to contact Crime Stoppers on 1800 333 000, as this information could be key to furthering the investigation."

Mr Mikita said the weeks around the anniversary were always difficult for his family. His mother, Elizabeth Mikita, this week said she lived with hope someone in the community would "do the right thing".

"We all miss Mum desperately and think often about the way she died," she said.

"No human being, whether young or old, deserves that sort of horror to befall them, even in the so-called safety of their own home, and I don't wish that on anyone, even my worst enemies."

Mr Mikita, who has for years put up posters calling for information about his grandmother's killing, said he would continue to make sure the community didn't forget what happened to his family."

"I do live in the hope that sooner rather than later someone will find the nerve to call Crime Stoppers and dob in the murderers," he said.