He was told off by Judge Christopher Ryan for snickering as he was sentenced in the County Court to three years in youth detention on Thursday.

Co-accused Bradley Elmore-Jeffries, 22, was sentenced to three years in adult prison and will be eligible for parole after 21 months.

The pair pleaded guilty to recklessly causing serious injury to environmental scientist Elliot Harvey at a Brunswick nightclub in May 2017 after snide remarks were made about Mr Harvey's car.

Initially, prosecutors believe the assault was sparked by comments made about Mr Harvey's man-bun hairstyle, a style sported in court by Moresco, 20.

Judge Ryan said after an initial confrontation Mr Harvey had thought it appropriate to nudge Moresco, whose "reaction to that slight was one of immediate intimidation and violence".

While Mr Harvey raised his arms and tried to walk away, he was shepherded back to the group where Moresco punched him three or four times, hitting him at least once in the face.

He then stood back while Elmore-Jeffries "threw lots of punches".

Judge Ryan said random violence committed by young men drinking alcohol was common.

"It is usually brief and not premeditated but it has a profound and long lasting impact on the victim," he said.

Mr Harvey has felt "pathetic" about his ability to work since the attack, can no longer enjoy sports like surfing and most nights drinks himself to sleep.

Judge Ryan stopped during the sentence to ask if Moresco found his comments amusing. He earlier warned him to keep his hands in his pockets next time he appears on television, referencing his outburst after a previous court appearance that the judge saw on the news.

Leaving court after the sentence, Elmore-Jeffries told his family he loved them, while Moresco said "I'll see you on the other side".

Australian Associated Press