A man who said his victim "was just a dog, who cares?" after fatally stabbing him outside a Wollongong methadone clinic has been jailed for at least eight years.
Michael Graham Gale made the "callous" remark immediately after stabbing his victim once in May 2018, although it was unlikely he knew the wound would be fatal, Justice Mark Ierace said.
Gale, 54, was charged with murdering Steve Edwards, 39, but the Crown accepted his guilty plea to the less serious charge of manslaughter by reason of excessive self-defence.
In the NSW Supreme Court on Friday, Justice Ierace jailed him for 12 years with a non-parole period of eight years.
According to the agreed facts, the two men had a history of animosity dating back to when Mr Edwards was sentenced for assaulting an elderly woman.
They both turned up before the methadone clinic opened when Gale initiated a fight, punching Mr Edwards, saying "this is for hitting the old lady".
During their struggle, Gale heard a noise, saw a knife on the ground and, believing it belonged to Mr Edwards, picked it up.
"The offender held the knife in his hand and stabbed the deceased once, causing a wound to the chest," the judge said.
After making the dog remark, he left Mr Edwards bleeding profusely at the scene and turned himself in to police four days later.
"Neither the offender nor the deceased was observed carrying or possessing the knife, one was not located at the scene and the weapon was never recovered," the judge said.
Gale had a deprived childhood and a long criminal history which included knife offences and the malicious wounding of a man he stabbed in the back of his head.
The stabbing was "disturbingly similar" with the previous offence as that victim had not initiated the encounter, the judge said.
The Crown accepted Gale had believed that stabbing Mr Edwards was necessary to defend himself, but that this response was not reasonable in the circumstances.
A mental health expert found Gale had conditions including being hyper-vigilant and perceiving innocuous events as possible sources of harm and threat.
"I find there was no provocation by the deceased," the judge said, noting statements from relatives who spoke of their grief over the death of Mr Edwards.
While the offence was spontaneous and unplanned, he said Gale had initiated and escalated the encounter in a public place in front of other people.
Lifeline 13 11 14
beyondblue 1300 22 4636
Australian Associated Press