Vincent Skeen swung a lethal broken beer bottle at Luke Tipene at least seven times and literally went for the jugular, the Crown says.
But Mr Skeen's lawyers say he swung blindly and delivered a single blow with no intention to kill.
Today, the jurors in the High Court in Auckland heard closing arguments from the Crown and defence in the case of Mr Skeen, who, at age 18, denies a charge of murder.
The Crown's case is that Mr Skeen was angry and embarrassed when he was punched to the ground by Mr Tipene, a promising young rugby league player, during a street fight on Halloween night in 2014.
Crown prosecutor Brian Dickey told the jurors there was evidence Mr Skeen went behind a parked ute on the side of the road and smashed a beer bottle to fashion a weapon.
"Getting the better of the situation, having the advantage of a weapon and the extended reach by virtue of that weapon but also a lethal blade, he thrust it ... the shard of that weapon deep into Mr Tipene's throat."
Mr Skeen swung the lethal weapon at least seven times, he said.
That was backed up by witnesses who watched the fight from a balcony and the pathology which showed a catalogue of injuries on Mr Tipene's body, he said.
"He aimed for the neck. He went for the throat. He literally went for the jugular."
He said the Crown's case was that the wounds spoke for themselves and Mr Skeen's intentions.
"If we needed anything more at all, we could look at his words ... just after the event, he tells the ensemble, he announces - if you like: 'I've just stabbed the ****'. There's no suggestion of: 'I've just made a terrible mistake'."
Mr Dickey said even if they did not find Mr Skeen intended to murder, he knew that his actions could have led to Mr Tipene's death and went ahead anyway.
"The Crown says that's murder and needs to be called what it is. Yes, Vincent Skeen was a young man when this happened but that won't make what is murder not murder."
No intention to kill, defence lawyer says
But Mr Skeen's lawyer, Lorraine Smith, said her client had no intention to kill.
"When Vincent Skeen was 16 years old, he picked up a bottle and he hit another boy with it. That boy tragically died and this tragedy changed the lives of two families forever."
Ms Smith said her client had always accepted that what he had done was wrong.
But she said Mr Skeen never aimed at Mr Tipene's neck and the Crown had overstated the evidence.
"The other very realistic probability, or possibility, is that Vincent was swinging out blindly without any intent to connect with any particular part of the body. Please don't forget for a moment how fast this all happened."
She said Mr Skeen had been drinking and had been punched in the head so hard that one witness described him as being in la-la land.
Mrs Smith also reminded jurors about what Mr Skeen said to his friend, shortly after the stabbing.
"And what he says is not anything boastful, not anything triumphant, not anything gleeful. He says: 'I've caked it ... I've stuffed up.'"
She pointed to the inconsistent evidence from witnesses to the fight and reminded the jurors that they had to be sure beyond reasonable doubt, and if they were not they must find her client not guilty.
On Monday morning, the jurors will hear a summing up from Justice Peters before retiring to consider their verdicts.