Sheffield, 56, who pleaded guilty to murdering Kenneth Magee on December 2, 2024 in their home in Melbourne's west, was on Thursday sentenced to 22 years in prison with a non-parole period of 16 years.
Mr Magee had been Sheffield's informal carer who took him to appointments, helped shower him and cooked and cleaned at home, with a former neighbour describing the pair as co-dependent.
The 62-year-old was sitting in the living room of the Werribee home when Sheffield, who has been diagnosed with schizophrenia, bludgeoned him with a hammer.
A neighbour heard shrieking from the house at 6.50pm before Sheffield called police about 20 minutes later. They arrived to find the victim lying unconscious on the couch with severe head injuries.
He was rushed to hospital but succumbed to his traumatic injuries, including skull fractures and brain lacerations from at least five blunt impacts.
In sentencing, Justice Rita Incerti said the terrible tragedy has had a devastating impact on Mr Magee's family.
"This is a serious example of murder ... It was a brutal assault on Mr Magee in his own home where you tried to cause serious injury to him," Justice Incerti told Sheffield.
The judge accounted for the murderer's age, ill health and early guilty plea when she imposed a below-standard jail term, saying she had to balance a sentence that would not be "crushing".
While she believed the sentence was fair and considered, Mr Magee's sister Allison Menzies said it was cold comfort for the family.
"It will not bring Ken back, and I have to live with the horror of how my brother died," she said outside court.
"Bad people do evil things, and good people have to suffer the consequences of those evil things.
"This is our life, but we have lived with this for quite a while now. We just want to heal."
Mr Magee's daughter Kristy can finally breathe after a gruelling experience navigating the justice system.
"I have no other words but perfect. It's where he needs to be," she said.
She hopes Sheffield thinks of his day of reckoning every day in his prison cell.
"I kind of hope it really gets in his head," she said.
Sheffield initially told police someone had broken into their home while he was in his room listening to a John Farnham DVD loudly.
He said he went outside for a cigarette and returned to ask if Mr Magee wanted one when he found his "mate" on the couch with blood coming out of his head and a hammer next to him.
Detectives found no signs of damage to the doors at the house and arrested Sheffield.
He was taken to hospital the next day for diabetes complications when he asked the accompanying guards if they had caught the murderers, before asking how someone finds a murderer if he leaves his prints on the hammer.
Sheffield told the officers he wanted to change his story, saying he had pulled the hammer out of Mr Magee's head and placed it on the couch and his prints would be on it.
The defence had pointed to previous statements and reports from neighbours and a domestic violence group about Mr Magee allegedly abusing Sheffield.
The prosecution urged the judge to be cautious about the violence claims, saying Sheffield had lied to police before and referred to a hospital report stating he had denied any concerns about his carer.
Justice Incerti contemplated evidence pointing to their relationship being turbulent and abusive but couldn't conclude, on the balance of probabilities, this was the case in the lead-up to the murder.
Sheffield has already served 521 days in pre-sentence detention.
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