Key Points:

Minutes after the lawyer for a convicted teenage killer told a court of his remorse, the youth gave a one-fingered salute and swaggered out of the dock to start a life sentence with a minimum non-parole period of 11 years.

Petani Fa'avae was 16 when he used a switchblade knife to stab 14-year-old Manaola Kaumeafaiva in the heart outside a dance competition at Avondale College in Auckland on October 22, 2006.

Manaola fell to the ground and died within minutes as he lay in the arms of his best mate.

In the High Court at Auckland today, Fa'avae's lawyer David Niven told Justice Christopher Allen that Fa'avae, now 18, was remorseful and wanted to meet his victim's family to formally apologise.

However, after he was sentenced, Fa'avae swaggered out of the dock and made a one-fingered gesture at the media bench.

He showed no remorse as he sat in the dock in No 14 Court for more than two hours and listened to Mr Niven argue for no additional non-parole period to go with the mandatory minimum life sentence of 10 years.

He also heard the victim's best friend tell the court how he cried as he held Manaola in his arms with his hand over the chest stab wound.

Walter Ngan-Woo said he was shocked, angry and puzzled over the unprovoked attack.

"I would like to ask `Why did he kill my friend?"' he read to the court from his victim impact statement as Fa'avae sat impassively in the dock.

He told the court he still felt angry and guilty that he could not do anything to help Manaola.

During his sentencing Justice Allen said Manaola had done nothing to attract Fa'avae's attention and was in the wrong place at the wrong time.

He was stabbed in the heart with sufficient force to bury the knife up to its hilt.

Others managed to flee but another victim was badly cut on the arm when he tripped as Fa'avae chased him.

He said Fa'avae had been part of the Crips which was a gang of ruthless young thugs loosely based on an American gang.

He left school at 15, was sent to Australia by his parents who were worried at his behaviour but came back to New Zealand and continued his involvement in alcohol and drugs.

He said Fa'avae drank wine with others from south Auckland and then went looking for trouble.

"This is precisely the sort of crime that strikes at the foundation of a decent society," the judge said.

Fa'avae was sentenced to life in prison with an 11-year, non-parole period on the murder charge, six years in prison on a charge of wounding with intent, and six months on each of two charges of assault with a weapon. All the sentences will run concurrently.