An officer who "leg swept" an alleged Ashburton drunk driver during an arrest used "excessive force", an investigation by the Independent Police Conduct Authority has found.
IPCA chair, Judge Colin Doherty, found the officer did not act in accordance with police policy after the incident in the town on July 21, last year.
Police say they accept the findings and the officer went through an internal employment procedure, however he had since resigned due to "unrelated reasons".
Police were called to an area in the town about 9.20pm after reports of a man "behaving strangely" and believed to have crashed his car into a bollard.
Two officers arrived at the scene to find the driver, 59, had blood on his face.
After failing an alcohol breath test, he had to be forcefully removed from his car and taken back to the Ashburton police station.
While police actions in removing the man from the car were lawful, an officer's behaviour at the station was not.
One of the officers moved the man to face a wall as he believed the man was threatening and intending to "smack" him or spit blood at him.
The officer told the authority he feared for his safety so he leg-swept the man off his feet, causing him to land face first on the ground.
On the way down, the man hit his face on a wall heater, causing him to bleed heavily from his face. The man was handcuffed behind his back at the time.
"The officer did not act in accordance with the law and police policy when dealing with Mr X in that the force he used against Mr X in the charge room was not in self-defence and was unjustified," Doherty said.
The authority also found that there was a delay in seeking medical attention for the man which was unacceptable.
Canterbury District Commander John Price said their own investigation found the officer's actions did not reach the standards expected by police when caring for people in police custody.
The officer was subjected to an employment investigation under the NZ Police Code of Conduct and was returned to frontline duties, but has since resigned from police for unrelated reasons.
"I acknowledge this IPCA report and we will learn from its findings," Price said.
"We also acknowledge that the use of force in this incident was not proportionate and that medical assistance was delayed in this instance due to the focus on obtaining an evidential breath test.
"I also note that the man was provided with the appropriate medical assistance once in hospital.
"Our staff are constantly put in difficult situations, and although these dynamic situations can develop in a matter of seconds we expect police staff to act professionally.
"It is expected at all times our behaviour and actions model police values.
Unfortunately in this matter, the officer did not and has been held to account."
