A West Australian police officer who used a chokehold while arresting a young man, causing him to lose consciousness, has been found to have used excessive force.
WA's Corruption and Crime Commission (CCC) has found the actions of Senior Constable Valleekanthan injured the complainant, referred to as Mr A.
Findings of serious misconduct have been made against him and another officer, First Class Constable Harrison, in a report tabled in parliament on Thursday.
The pair had intervened in an altercation between Mr A and his friends and a second group of people in an open-air carpark in Northbridge in November 2019.
Mr A was told he was under arrest for disorderly behaviour after verbally abusing the officers as they arrested his friend, Ms Y.
Members of his group attempted to pull the officers away from Ms Y and Const Harrison drew his baton, warning them to stay back.
Mr A "appeared calm" as he retreated while recording the officers' actions on his mobile phone.
Snr Const Valleekanthan followed Mr A and applied a Brazilian Jiu Jitsu "seatbelt hold", testifying that he had wanted to turn him around.
He testified that he felt Mr A's left arm move and responded by altering his grip.
The report described footage of Snr Const Valleekanthan applying a chokehold with sufficient pressure to activate his body-worn camera.
Mr A fell forward and the officer fell on top of him.
"Mr A's head struck the bitumen of the car park. His fall forward appeared unsupported," the report said.
"Mr A does not appear to have attempted to extend his arms to break his fall, which indicates that he may have been unconscious at the time."
He sustained a "significant" cut to his forehead, a black eye, bruising and scratches but was left sitting handcuffed at length without medical attention.
Police records claimed Mr A was in custody for just one minute, and did not record his injuries.
WA Police officers were only permitted to use a neck hold restraint if there was an imminent risk of grievous bodily harm or death.
Snr Const Valleekanthan had never been trained in such a hold by WA Police.
"It was not reasonably necessary to effect the arrest or overcome Mr A's limited resistance to it," the CCC said.
A finding of serious misconduct was also made against Const Harrison after he issued a move-on notice to Mr A's partner without proper basis.
Mr A was fined after pleading guilty to disorderly conduct in Perth Magistrates Court.
Acting Deputy Commissioner Kylie Whiteley said the two officers were still serving but were no longer on active duty.
They are facing disciplinary proceedings.