Two police officers have been found guilty of assaulting a teenager after a trial in Auckland District Court.

The jury returned their verdicts on Gareth John Needham, 38, and Alan Michael Douglas, 32, after deliberating for about eight hours yesterday - 11 of the 12 jurors finding they were both guilty of assault.

The Crown alleged Needham and Douglas assaulted Joshua Hart, 18, who had been drinking with up to 50 people at a West Auckland park in February, prosecutor Hugh Leabourn said.

The charges followed complaints by two other officers who were sent there to disperse the crowd.

Mr Hart last week told the court Needham punched him in the head after he swore at the officer when he knocked a drink out of his hand.

He told the court he called the officer a "faggot" - angry about losing his last drink - after which Needham punched him in the head.

Mr Hart said he then tackled Needham and the two scuffled on the ground until he was restrained and arrested.

Needham then punched him in the head again, Mr Hart said.

Douglas became involved when the teenager started insulting officers as he was being escorted to a police van and Douglas "essentially lost control" and punched him in the face, possibly more than once, Mr Leabourn said.

Douglas then told other police officers to take Mr Hart's handcuffs off so that they could have a fight.

Douglas' defence argued he merely pushed Mr Hart's face away because he was going to spit at or headbutt the officer.

Needham's defence argued he had hit the complainant with an open hand as a "diversionary tactic" so that he would be able to put handcuffs on him.

The trial was expected to take three days but lasted seven.

Figures in July this year showed that more than 200 police were under investigation for assault and using excessive force.