The 18-year-old, whose name is permanently suppressed, attacked 15-year-old Stephen from the side after a rugby practice -- punching him in the neck and continuing the attack while Stephen was on the ground.
Justice Helen Winkelmann indicated early in the sentencing process she would grant the teen a discharge without conviction, to the anger of the Dudley family in the public gallery.
"You're f***ing joking," his father Brent Dudley shouted.
"His actions caused my son's death . . . That's justice for you New Zealand. The law's an ass."
A 16-year-old boy previously came before the High Court after also admitting assaulting Stephen.
He too was discharged without conviction earlier this year.
The 18-year-old was to have faced trial for manslaughter but in June pleaded guilty to an amended charge of assault with intent to injure.
West Auckland boy Stephen died after a school rugby training session on June 6 last year.
An argument between he and the 16-year-old looked likely to result in a fight, which attracted the older boy to the scene.
After he and the other boy launched a sustained attack, the pair left Stephen on the ground unconscious.
He did not throw a punch.
He was rushed to Auckland City Hospital but died a short time later.
Critically, medical examinations showed an undiagnosed heart condition contributed to his death.
As a result the Crown withdrew the manslaughter charge against the older defendant after receiving two expert reports on cardiac pathology and arrhythmia.
Today the court heard emotional victim impact statements from Stephen's mother, father and sister.
Brent Dudley was particularly critical of the teen's actions, calling him "the hand of evil" while staring at him in the dock.
"The actions you took were nothing but cowardice and brutality," he said.
"He was a lot smaller than you and you attacked our son from behind. He had no idea about the attack he was to be subjected to.
"Any thoughts of forgiveness are out of the question at this stage. I hold you entirely responsible for the death of our son . . . you own that."
Defence lawyer John Munro said his client had been excluded from school and experienced severe social isolation because of what happened.
He called it "a very very poor error of judgement" and stressed how much he had learned from the experience, giving speeches to young people at his church about the consequences.
The sentencing closes the legal chapter on a 14-month trauma for the Dudley family during which Stephen's mum Mona also appeared before the court when she actually shot her husband Brent with an airgun while they argued.
She was eventually discharged without conviction but the pellet which lodged inside Brent Dudley's chest was left by doctors because of its proximity to his heart.
- Rob Kidd of APNZ
