A police officer avoided conviction despite repeatedly punching an arrested man and kneeing him in the head.
The Independent Police Conduct Authority found the officer was repeatedly and gratuitously violent towards the man.
The 43-year-old officer was called to a disorder incident in central Auckland involving a drunk man on 24 August 2018. When the officer tried to make an arrest the man punched him.
With the help of other officers, the man was detained and taken back to the station.
During the transportation the officer repeatedly punched the man's face, kneed him in the head, and shoved his face into a concrete wall, the Independent Police Conduct Authority found.
At the police station the officer hit the man with an uppercut to the face. This was captured on CCTV.
A police employee present at the time said the officer then threatened to kill the man.
The officer denied threatening or punching the man, despite footage of the latter.
He was charged and pleaded guilty in court to two counts of common assault, after two other charges were withdrawn, and one of threatening to kill.
The officer was discharged without conviction at sentencing in January this year.
Police said the man was the subject of an employment investigation following court proceedings but resigned before this was completed.
Superintendent Karyn Malthus, Auckland City District Commander, said police agreed with the IPCA's findings that the officer used excessive force following the arrest.
"I fully acknowledge that on this occasion the officer acted out of line and abused his position of authority. It is never okay for our officers to act, or react, in a violent manner.
"I also want to reassure the public that any allegations involving inappropriate conduct of a police officer will be thoroughly investigated and appropriately dealt with."