He unknowingly made that admission to undercover police shortly after his arrest and 20 months later, he has pleaded guilty to manslaughter in court.

Allan, now 25, maintained an expressionless face as prosecutor Kevin Doyle told Wangaratta Supreme Court on Wednesday how Mr Berry was attacked during a street brawl on White Street in the early hours of the morning.

The fight started when Allan and cousin Christopher Meaney thought Mr Berry simply calling out to his friend “Boo Boo” was a slur directed at them.

Meaney struck Mr Berry, before the victim’s friend Paul Kerr joined the fight with two machetes.

When Mr Berry asked Allan “what was that for?”, Allan responded by punching him to the ground and stomping on his head.

After helping Meaney fight with Kerr, Allan returned to an unconscious Mr Berry who was lying in the middle of the road.

“Mr Allan then kicked the deceased to the upper body and head and stomped on the deceased’s head more than once,” Mr Doyle said.

He said three undercover officers were also placed in the Wangaratta police cells when Allan was arrested.

“I knocked two of them out and jumped all over their heads,” Allan told them.

“I just went mental, I just went all out.”

Mr Berry’s parents Edward and Jeanette Berry were brought to tears as their victim impact statements were read aloud in the court.

“Nothing will ever be the same for us because we have a piece of our family missing,” Mrs Berry said in her statement.

“Our son hurt no one.

“He was quiet and he was friendly … He didn’t deserve to have his life cut short.”

Allan’s barrister Rishi Nathwani said although his client initially denied the stomps when interviewed by police, he also immediately expressed remorse.

He revealed Allan had been diagnosed with a form of cancer called Burkitt's lymphoma while in custody, but after stem cell transplantation and chemotherapy, he was now in remission.

“As a result of this incident, he’s grown up significantly,” Mr Nathwani said.

“He wants to come out as a person who can provide and contribute to society, and put behind his criminality.”

Justice Lex Lasry said he accepted Allan was a conscientious prisoner, but the offending was “extremely violent and unjustified”.

“This is a case where the incident developed relatively spontaneously,” he said.

“This is happening every day around Melbourne.

“These people just can’t help themselves, which means deterrence is a relative factor.”

The case will return to Wangaratta Supreme Court on Thursday for Justice Lasry to hand down the sentence.

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