A police officer used excessive force when he put an intoxicated woman in a headlock and pulled her to the ground in Invercargill last year, the Independent Police Conduct Authority has found.
The authority said the officer was "retaliating in anger" against the woman, who had been drinking in a liquor ban area.
Four officers approached the woman and her three friends at about 11pm on 25 July 2020, when they were drinking in a forecourt. The officers told the women to pour out all their alcohol, the authority's report on the incident said.
One officer, known as Officer A, admitted he may have called one of the women a "silly bitch" during a verbal altercation.
The authority found he used "unprofessional and inappropriate language" to the woman, escalating the situation.
The woman kicked some empty cans and the officer grabbed her arm and arrested her for disorderly behaviour.
Officer A claimed the woman tried to hit him, but the authority found CCTV did not support his account and he was not acting in self defence.
The officer put the woman in a headlock, pulling her backwards onto the ground.
The authority said it appeared the woman kicked the officer as she struggled to get him to release her.
She was handcuffed while on the ground.
Another officer said Officer A suddenly grabbed the woman by her handcuffs and "wrenched her up off the ground" and the woman screamed.
The woman had "significant bruising and a welt" and on her wrists, injuries probably caused while she was handcuffed, the authority said.
The officer was "unnecessarily rough" with the woman, the authority said.
She was taken to Invercargill police station, but was later released with a formal warning.
Authority chairperson Judge Colin Doherty said the force the officer used would have been "disproportionate and excessive", even if he had been acting in self defence.
"The officer's frustration resulted in him using force which good policing would have avoided," he said.
The police have acknowledged and accepted the findings.
Southland Area Commander, Inspector Mike Bowman said using a headlock was not an approved method of restraint.
"The actions of the officer have not met the high standard we have of our staff," Bowman said.
A criminal investigation has been completed and a decision made not to file any charges against the officer, following the recommendation of a national advisory panel.
The officer is undergoing an employment investigation.