A man jailed for killing a cyclist in a 2011 hit-run incident also killed a father of five, then hid his body in bushland on Melbourne's outskirts, that same month.

Daniel Veerman, 37, had already been found guilty of causing the death of one man in March 2011 when police interviewed him over the murder of Kyal Scanlon, 29, who disappeared around the same time.

Mr Scanlon left his Kilsyth home to get food vouchers on March 7, 2011 and never returned.

His badly-decomposed body was found concealed in bark and leaves at Olinda in Melbourne's outer east 12 days later.

Veerman was charged with Mr Scanlon's murder, but this charge was dropped when he pleaded guilty to manslaughter in the Victorian Supreme Court last month.

At a plea hearing on Friday, Mr Scanlon's family heard they may never know exactly how he died.

There were no witnesses to his death, and the autopsy was unable to determine the cause.

Crown prosecutor Christopher Dane fought back tears as he read the statements of Mr Scanlon's five children.

One of Mr Scanlon's daughters said she felt like her heart had been slowly cut in half.

One of his sons spoke of how his dad used to take him to a local school to kick the footy, and now he didn't want to kick the footy any more.

Another of Mr Scanlon's daughters, who was three years old when he died, said she couldn't remember him.

"I wish I got to see my dad more," she said in her statement read to the court.

Mr Scanlon's partner, Kristy Coyne, said her children had nightmares since their father's death and she had been robbed of the chance to grow old with her soulmate.

"He didn't just take Kyal away from us, he took a piece of our souls," Ms Coyne said in the statement.

Defence barrister David Hallowes said Veerman had significant mental health problems due to a long-standing drug habit.

"There's likely to have been some impairment to his judgment at the time of the offending," Mr Hallowes said.

Veerman's mother and the family and friends of Mr Scanlon cried throughout the hearing on Friday.

Veerman appeared impassive.

One man, in court to support the Scanlon family, lashed out at Veerman's mother.

Justice Elizabeth Hollingworth will sentence Veerman on a date to be set.