"I had already lost an adult son to an illness, but to lose another in the most cruel and vicious way was very hard to accept," Pat Welsh said in her victim impact statement.

Her statement, as well as statements from two of her daughters, were tendered at the NSW Supreme Court sentence hearing of Luke Close on Friday.

After a judge-alone trial, the 33-year-old Sydney man was found guilty in August of murdering Garry Welsh, 63, in February 2018 at his Nowra unit on NSW's south coast.

Close's partner had referred to the men as being "drug buddies".

Although it was accepted he had no memory of the stabbing, Close had pleaded guilty to the less serious charge of manslaughter which was not accepted by the Crown.

Justice Richard Button found Close was "was grossly intoxicated with alcohol and various drugs before, during and after the homicide and that the fatal acts had "a flavour of frenzy to them"".

"Even so, I am compelled to the firm opinion that his mind was engaged with what he was doing," he said.

Close had forcefully inserted a knife or knives into "a frail old man, who must have been bleeding copiously as a result" and also inflicted many other injuries by violence.

Describing finding out about the murder as "the worst day of my life", Ms Welsh said she was admitted to hospital with a suspected heart attack three days later.

"But further tests proved it to be 'broken heart syndrome' which never goes away."

The family did not learn of the extent of her son's injuries sustained in the "very cruel and frenzied attack" until just before the start of Close's trial.

"I can't for the want of trying erase that vision from my head. It's with my day and night," she said.

Her daughter, Kim Gough, said she didn't know how anyone could do what Close did to her big brother.

"I don't believe that they were mates. Garry was just being used and that makes me very angry and sad," she said.

Another sister, Christine Laird, said she hoped the terrible images of the attack would fade from her mind in time.

"I love you Garry and I'm so sorry that this barbaric thing has happened to you," she said.

"You will remain on that pedestal I put you on so many years ago. Your murderer didn't just kill you, he also killed a piece of me."

Close wrote a letter of apology to his victim's family and friends, saying he was sorry for "the pain and heartache he had caused".

In the letter, tendered to the court, he said he hoped they could forgive him one day.

While he couldn't imagine the grief and sadness he had caused them, he said he did compare it to when he lost his mother which was "the worst feeling I've felt in my entire life".

Justice Button will sentence Close on November 6.

Australian Associated Press