The court was told that Aiono, his wife Tausilia, their baby son, Mr Sanato and another man had all moved into a house together in December 2008.
Early in 2009, Aiono travelled to Samoa to take care of family matters, and while he was away he became suspicious that his wife was seeing other men.
His suspicions were proved correct. The court was told she had had consensual sex with Mr Sanato.
However, she told Aiono that Mr Sanato had raped her.
During his first trial, she told the court that she continued to tell him she was raped, but at the second and third trials she said she eventually admitted that the sex was consensual.
The court was told that Aiono's brother drove him to Mr Sanato's Manuerewa house on the evening of February 25.
Aiono told police he confronted Mr Sanato in the garage, who refused to apologise and threw a punch.
The men fought and Aiono overpowered his friend, punching him repeatedly until he fell to the ground, face up and unconscious.
He then stomped repeatedly on his head.
The attack was witnessed by a young boy who was in the house, who said Aiono also beat him with a lump of concrete. However, Justice Peters found there was insufficeint evidence to support this claim.
Crown prosecutor Christine Gordon said it was unarguable that Aiono knew he had rendered Mr Sanato unconscious yet he continued beating him.
"This was not the case of a single blow or even several blows causing death. This was a case of a vicious, sustained and forceful attack which involved kicking, punching and stomping the head of an unconscious victim," she said.
"The victim was very quickly rendered unconsious and once he was in that state he was ... vulnerable and defenceless."
Defence lawyer Maria Pecotic said the attack had been "completely out of character".
She argued that it was not sustained, as the Crown had submitted, but "a frenzied attack and not prolonged".
Aiono, a church-going man, had been described in several letters to the court as "gentle, kind and good-humoured".
He had shown genuine remorse and reparation had been paid to Mr Sanato's family.
Aiono's family had also performed the Samoan ritual of ifoga, where the offending party demonstrates remorse by begging for forgiveness.
Mr Sanato's family had forgiven Aiono, but they wanted him to learn to control his temper.
Justice Peters said this forgiveness was "extremely kind and generous" given the circumstances.
However, she did take into account several mitigating factors when imposing sentence.
"You might have expected more of him (Mr Sanato) because he was a close friend to whom you had shown considerable generositry.
"This was a case not of an intentional killing but one where you assaulted him in a manner in which you knew there was a real risk that you could kill him."
