Ethan Harwood stabbed his grandmother to death and ran.
From the 67-year-old woman's western Sydney home to Melbourne and then his mother's home in western Victoria, the then-teenager evaded police for five days until his arrest on December 7, 2017.
Initially hiding behind lies about an ice-fuelled blackout, Harwood ultimately came clean about his argument with the woman who'd raised him - and his use of kitchen knives to kill her.
More than 55 knife wounds were found on Pauline Farrugia, including a cluster on her back and half a dozen on her head and neck.
NSW Supreme Court Justice Michael Walton, who on Friday jailed the 21-year-old until at least 2029, said Harwood had gone to his grandmother's South Penrith home to "have it out" over his separation from his mother.
The young man had recently reconnected with his mother, who'd blamed her mother, Ms Farrugia, for their separation.
He'd also spent the afternoon drinking with two other estranged children of Ms Farrugia's before hitchhiking to his grandmother's.
The meeting began amicably. Ms Farrugia offered her drunk grandson a glass of wine and put on a DVD from the pair's holiday to Hawaii.
But things changed when Harwood brought up a minor falling out with his uncle earlier that day, the judge said.
According to Harwood, his grandmother said he was "ungrateful" and she had been right that he would "never amount to anything".
"The attack did not involve any degree of planning, sophistication or premeditation but rather bore all the hallmarks of a sudden, impulsive assault, accompanied by a catastrophic loss of control, by an immature, isolated and emotionally conflicted young man," Justice Walton said.
He said regardless of the killer's suggestion his grandmother was emotionally abusive, Ms Farrugia was a victim of a violent attack.
"It is clear from the evidence that (Ms Farrguia) was a complex personality and whilst her relationship with the offender had elements of friction or hostility at times, there were also elements of compassion and love," he said.
Identifying Harwood wasn't difficult for detectives.
As well as leaving his socks in the bathroom and his wallet on the stove, his blood or other DNA was found on four different light switches, two bedroom wardrobes, a smoke detector and in the kitchen.
He was captured on CCTV just hours after the murder, parking his grandmother's car near Penrith Station.
About a year after his arrest, he pleaded guilty to murder.
Justice Walton jailed the young man for 16-and-a-half years, with a non-parole term of 12 years, making him eligible for release in December 2029.
The young, socially naive and physically small Harwood had reasonably good prospects of rehabilitation, the judge said.