Crown lawyer John Dixon summarised the prosecution case for the jury.
He said Te Amo's punch, on the evening of February 26 on an Orakei street, caused Mr Nicholson's jaw to be broken as well as bleeding in his brain, which eventually led to his death.
"It's tragic... it's terribly bad luck for both of them but it's that simple," he said.
Mr Dixon accepted the Crown could not totally account for all the victim's movements in the day and a half that followed the brawl and that it could not be ruled out that he had another fight.
But he said that did not change the significance of Te Amo's punch.
The jury should pay close attention to the defendant's "reenactment" of the fight, which was recorded during the police interview, he said.
"It's powerful stuff," Mr Dixon said.
The court heard evidence of Mr Nicholson's propensity to get involved in fights and he had broken his jaw nine days before Te Amo allegedly rebroke it.
Ms Sellars said the victim had 27 convictions for violence and a history of head injuries, which made the medical and factual evidence "murky".
A fight on Karangahape Rd, a domestic with his partner and another incident on the same day as the Te Amo attack could have caused the injuries that led to his death, she said.
"We've got someone who we know was wandering around the neighbourhood drinking," Ms Sellars said.
"Alternative possibilities need to be discussed."
The Crown urged the jury to dismiss other potentially-violent altercations as guesswork but Ms Sellars was adamant.
"It's entirely reasonable and not speculation," she said. "Everyone agrees he was no stranger to a fight."
The defence lawyer was also highly critical of the police investigation, which she described as "piecemeal, extremely drawn out with big gaps between when people were spoken to".
"Some witnesses were not spoken to for years after the death. In those circumstances how can you be sure what was happening?" she said.
The jury will begin deliberations this afternoon.
