Michael Allan Ackerley, 50, has admitted to the fatal stabbing of Mathew Baum, 41, at a home in Lara, outside Geelong, in February 2020.

Mr Baum's mother Dianne Martin spoke on Friday about the loss of her son, a road worker and local cricketer.

"When I do sleep the dreams of Mathew are so real," Ms Martin told Victoria's Supreme Court.

"I awake with feelings of such joy ... to realise it is only a nightmare. And then the tears start and the overwhelming feelings of sadness return.

"The pain is still so real. It just doesn't go away."

Mr Baum's father Neville said he shuddered to think of the pain his son endured in his last moments, before addressing Ackerley directly.

"I hope the rest of your life is filled with the pain of regret of what you have done to our family," Neville Baum said in a statement.

Prosecutor Grant Hayward said Ackerley and Mr Baum had got into an argument in the house they shared with several others after drinking heavily throughout the night.

Mr Hayward said Ackerley, who earlier pleaded guilty to manslaughter, had deliberately struck Mr Baum once in the groin with the 47cm-long blade.

In a triple-zero call that was read out in court, Ackerley said Mr Baum had attacked him first in the belief he'd stolen his phone.

"I'm very sorry but he shouldn't have attacked me first," Ackerley said.

"He smashed me head into the concrete. A knife was beside me so I stabbed him - that was the only way to get him off."

The 50-year-old later told authorities he'd drunk more than five cans of Jack Daniel's that night.

The court also heard Ackerley took photos of Mr Baum as he lay in a pool of blood.

His sister, Kim Elaine Ackerley, said her older brother was illiterate and had never progressed further than year eight in high school.

Ms Ackerley added she once told her daughter he had the intellectual ability of a child despite being in a "grown man's body".

But she had never known him to show violent behaviour.

Ackerley's barrister, Jarrod Williams, said his client had a clear capacity to distinguish right from wrong, but was a "simple and concrete thinker".

"Mr Ackerley is a diminutive, intellectually disabled man who does not have the coping skills that (others) might have," Mr Williams said.

"That is ultimately reflected in the way he conducted himself on this occasion."

Ackerley will return to court for a further pre-sentence hearing.

Australian Associated Press