When the police knocked on the Rowville door of alleged murderer Steve Fabriczy, in Melbourne's eastern suburbs, on Wednesday morning, it was a vital DNA match which sent them there.
For years, ACT detectives had been looking to link the DNA evidence recovered at the scene of a brutal 1999 Canberra murder.
It emerged sooner than expected, but it wasn't until a comprehensive search of the national DNA database that the positive "hit" came.
A Dandenong court hearing this week provided the clue: Fabriczy was incarcerated between 2010 and 2012 after being convicted of a conspiracy to highjack a truckload of cigarettes in Victoria.
As a matter of course in Victoria, all those convicted of serious offences have their DNA taken and stored.
And now it will be revealed in the ACT trial to come, that sample had been forensically matched to an even more serious and earlier crime.
In the evening of Saturday, November 6, 1999, two men forced their way into the Grosvenor Crescent, McKellar home of elderly couple, Gregor and Irma Palasics.
The invaders bound and severely bashed them both, then ransacked the house looking for jewellery and valuables.
Irma, 72, tragically died of her injuries from that home invasion. Gregor was very badly injured and never fully recovered.
Detectives know from experience that the longer a case drags on, the more the trail grows cold.
But with one notable exception: forensic DNA.
The science around DNA forensic profiling is evolving almost every year and is now one of the most powerful investigative tools available to police.
It was more than 30 years ago that American geneticists discovered a region of DNA (the molecule that contains the genetic identity code in all life forms) that does not hold any genetic information and which is extremely variable between people.
The analysis of this variation, together with population genetic principles, allows forensic scientists to achieve a very high degree of identification accuracy. Certainly enough to determine that an accused, identified via DNA profiling, can't be mistaken for anyone else.
DNA degrades with prolonged exposure to sunlight, heat and humidity. So climate-controlled protection of old exhibits and samples - hair, blood, semen or flakes of skin tissue - is hugely important. Sadly, some cold cases don't enjoy that luxury simply because the investigators at the time couldn't begin to anticipate how powerful DNA forensics would become decades on.
It's a hugely complex science and one of the newest forms, the Polymerase Chain Reaction method (PCR), although still in the experimental stage, may well revolutionise the entire technology.
The PCR method can replicate the DNA in one cell multi-million fold, even if that sample is substantially degraded.
The key question which remains now, in the light of the alleged Fabriczy match, is how many more of Canberra's long-term unsolved homicides could be waiting for forensics to provide the breakthrough?
Here's a recap of Canberra's other unsolved homicides down the years, with the reminder that if any of these details jog a memory, contact Crime Stoppers on 1800 333 000.
Information can be provided anonymously.
On a warm late September day in 1966, six-year-old Allen Redston walked with his brother to buy an ice cream at the Curtin shops and was never seen alive again.
The body of Allen Redston was found wrapped in a roll of carpet in a creek bed in Curtin, between Dry and Service Streets, on September 29, 1966.
He wore a green and white floral dressing gown which was later found to have been dumped at a local tip by a resident.
His hands and feet had been bound, and he had died of strangulation.
There is significant speculation that Allen may have been a victim of convicted Victorian serial child killer Derek Percy, who was holidaying in Canberra at the time.
But this was never substantiated, Percy made no admissions and he died of cancer in 2011 whilst serving time.
Keren Rowland, 20, had spent the day at the Royal Canberra Show on February 26, 1971 and was planning to go to a party that night in Deakin.
But she did not show up.
She was reported missing by family members about midnight.
Keren's vehicle, a white Mini Morris 850 sedan was later located on Parkes Way, Campbell with no petrol in the tank.
Her remains were discovered in a shallow grave at the Air Disaster Memorial nearly three months later on May 13, 1971. The cause of death has not been established.
In March 2002, a canoeist paddling around Yarralumla Bay looked into the lake water and made a grisly discovery.
It was the dead body of 23-year-old Kathryn 'Kat' Grosvenor, weighed down with a concrete bollard removed from Anthony Rolfe Drive, Gungahlin.
She had died of multiple stab wounds.
Kathryn had gone missing six days earlier.
She lived in Nicholls and the night she went missing there were two unconfirmed sightings of her in the Gold Creek area including at the George Harcourt Inn, where she was thought to have purchased cigarettes between 9.05 and 9.15pm.
Three people were named during the inquest as persons of interest, but no one has ever been charged.
Susan Winburn was 45 years old when she was strangled in her home at 81 Knoke Avenue in Gordon on January 13, 2004.
She was discovered naked in the bathtub by her sister after the victim had failed to turn up to work that day.
Susan, a member of the local church and a "gentle soul" was last seen alive purchasing items from a chemist in the Erindale Shopping Centre, Wanniassa about 7.10pm that evening.
There were no signs of forced entry to her home.
On Sunday, May 1, 2005, off-duty taxi driver Frank Campbell had some drinks at the Mawson Club and walked home to his unit in nearby Wilkins Street. He had visited two other clubs that same day to catch up with friends.
His flatmate came and went from the home around 11.30pm, then returned about 3am.
He found Frank dead of blunt force trauma. It appeared he had been struck 11 times on the head with a heavy item of some kind, possibly a frypan. A small sum of money had been stolen from the unit.
Sign up for our newsletter to stay up to date.