Man jailed over 'unreasonable' fatal stabbing

A convicted killer has almost four years to pursue his new goal of becoming a "normal person", jailed after overreacting and killing a man he supplied drugs to.

Jay Lupton, 31, pleaded guilty to manslaughter following two murder trials where juries were unable to reach verdicts.

He stabbed and killed Hady Jaouhara at a Lethbridge Park home in Sydney's west in February 2020.

In the NSW Supreme Court on Thursday, Justice Desmond Fagan jailed Lupton for nine years with a non-parole period of six years and nine months, backdated to May 2020.

Lupton crossed his arms as he stood to be sentences and was allowed to hug his daughter and kiss her cheek from the dock one last time before returning to prison.

The judge accepted Lupton acted in self-defence but out of proportion to the threat.

"(His) conduct was unreasonable by a very great margin," Justice Fagan said.

Lupton said he was being punched and kicked by Mr Jaouhara and another man before he opportunistically grabbed a knife, swinging it back and forth and stabbing Mr Jaouhara.

The conflict was sparked by Lupton finding the men smoking methamphetamine in a house where his daughter was also present.

His stated desire to prevent her exposure to drug use was "futile".

"Every adult resident of the place was a longtime, heavy user of methamphetamine, as (Lupton) was himself, and he was their substantial supplier," he said.

Earlier that month, Lupton had threatened to "stab the f*** out of" the two men, Justice Fagan said.

He had also punched Mr Jaouhara through his driver's side window, taken his keys and scratched "DOG" on the hood of his car out of jealousy.

The judge said Lupton could have continued to shield his head from blows or fight back in kind with his hands and feet, but picked up the knife and intended to cause grievous bodily harm.

Crown prosecutor Adrian Robertson read a victim impact statement from Mr Jaouhara's sister at an earlier hearing, describing how her brother was "belittled" throughout trials and referred to as a "junkie".

Mr Jaouhara did everything he could to help his mother cope with her depression and lived with his own, lamenting weeks before he was killed, "my mum deserved so much more than this world offered her".

"Now we know, so had you," his sister wrote.

Lupton told the hearing he did not care what sentence he received, but would spend it focusing on plans to "get a job and be a normal person" upon release.

"I've never wanted or had the chance to do that," Lupton said.

"The way I've grown up, I've had a hard life, I've never wanted to change."

"I just thought 'who cares' and gone back to drugs."

Justice Fagan said Lupton requires a "very significant personal upheaval" to prevent him reverting to crime.

His barrister Carolyn Davenport SC said Lupton was in danger of "becoming institutionalised" after being in and out of prison for much of his life.

Lupton agreed he previously had opportunities to rehabilitate but did not take them.

He has almost four years to take advantage of his latest chance before becoming eligible for parole on February 6, 2027.