John Mikita was 25 and "warm, comfortable and dreaming" when he awoke to hear police knocking at the family door to announce his grandmother had been killed in a brutal home invasion.

He listened in bed to police break the news to his parents in the room next door, and within seconds his eyes swelled up.

"I began to sob and quite quickly could not hold back the build-up of tears and emotions that had instantly built up inside of me," he said.

The pain has not gone away 16 years later, but with the case of his grandmother Irma Palasics' murder still unsolved, his hope of ever finding the two balaclava-clad thugs who broke into the McKellar home on the night of November 6, 1999 has ended.

"There's no more leads to go on as far as we're concerned … personally I don't know where it goes from here, I don't have any hope that there is anywhere it can go," he said.

In a letter this week, Mr Mikita shared publicly for the first time his feelings about the devastating events and how they have forever changed his world.

"I cannot put my finger on how exactly I felt for the hour or so after hearing the news, but I am sure it is much the same as I now sit here at my computer and typing these words fight to hold back breaking down and turning into a huge emotional mess with tears streaming over my cheeks," he said.

"How does anyone recover from a life changing event that is both confronting and horrific?

"Is their faith in humanity possible to recover?

"When no one comes forward to claim responsibility for their acts or people who know what they did hide in the darkness and fail to realise what is right from wrong."

Mr Mikita described the effect on his grandfather Gregor, who was also beaten severely in the attack and placed under police guard at Calvary Hospital.

"I think in reflection he also died on that night," he said.

"Everything that he knew was ripped from him and his will to live and function in normality was irreversibly destroyed.

"It amazes me he managed to survive for so many years after [Gregor died in 2004], but quite often he would intimate that he did not want to be alive any more."

Only a year ago there seemed to be reason for optimism that Mr Mikita's grandmother's killers would be found.

Fresh forensic evidence had led police to go public to call for clues, including nationally on 60 Minutes, with ACT Policing detective Senior Constable Jarryd Dunbar, the officer in charge of the murder investigation, believing it was "inevitable" police would find the attackers.

Police announced in July the investigations into a familial DNA link had ruled out a suspected connection between the 1999 attacks and a break-in to the Phillip Putt and Play in 2010.

"The 60 Minutes report last year and everything was very, very hard," Mr Mikita said.

"I put all these posters and everything up, and I had hope, and I thought people would just do the right thing after the story."

Information from the public had allowed police to close several lines of inquiry and also helped identify several people of interest in parts of NSW and South Australia. Senior Constable Dunbar maintained it was only a matter of time before advances in DNA evidence led to the killer.

But Mr Mikita, who still lives in Canberra, can only cling to the memories of his grandmother, even as those reminiscings remind him of what he and his family have lost and how they have been changed.

"My huge outpouring of emotions was so great back in 1999 that today I rarely show emotion about anything anymore," he said.

"Last Friday night at 9.30pm, like the rest of our family I remembered Grandma and Grandpa for the hard working, caring, loving and wonderful people they were," he said.

"For the many wonderful times I spent all my sick days and school holidays with my Grandma shopping, eating donuts and watching Days Of Our Lives (begrudgingly).

"It's the happy memories that continue to inspire me to live my life as best I can, the murderers of grandma cannot take those so tragically from me like they took her life."

Police ask anyone with information on Mrs Palasics' death to contact Crime Stoppers on 1800 333 000 or at act.crimestoppers.com.au. Information can be provided anonymously.