A young Sydney man who murdered the woman who raised him and then fled to Victoria could be released in a little over 10 years' time.

Ethan Harwood, now 21, used multiple knives to stab his 67 year old grandmother Pauline Farrugia more than 50 times - many of which were in the back - after she welcomed him into her South Penrith home in December 2017.

After leaving blood stains on several light switches, a safe and the stove, he made his way to Melbourne and then his mother's home in rural Victoria.

Ethan Harwood ( pictured ) was sentenced to a minimum of 12 years imprisonment for the murder of his grandmother

Ethan Harwood ( pictured ) was sentenced to a minimum of 12 years imprisonment for the murder of his grandmother

He was arrested five days later and eventually pleaded guilty to murder in the NSW Supreme Court.

Justice Michael Walton accepted Harwood's submission there was no planning or sophistication in the offending, which had all the hallmarks of a 'sudden and catastrophic' loss of control by an immature and emotional young man.

But he said regardless of the killer's suggestion his grandmother was emotionally abusive, Ms Farrugia was a victim of a violent attack.

He 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.

Justice Walton said Ms Farrugia had raised the killer from an infant until about a year before her violent death.

On the evening of her death, she welcomed her drunk grandson into her home, offered him a glass of wine and put on a DVD of the pair holidaying in Hawaii.

But the pair argued and the heavily intoxicated Harwood responded with knives.

Judge Walton said the young, socially naive and physically small Harwood had good prospects of rehabilitation.