Auckland man Taniela Feaomoengalu needed treatment for concussion and an eye injury just hours after being arrested outside an Onehunga bar.
The 37-year-old was also later treated for a bruised chest by a GP.
But police deny they inflicted the wounds, and an Independent Police Conduct Authority (IPCA) probe also failed to find any proof that officers had assaulted him.
For two years, the 37-year-old has pushed for answers after the incident claiming they were suffered while in custody after being arrested for disorderly conduct.
A police spokesperson said any suggestion of police assault is completely wrong and not backed up by any evidence or witnesses. However, the spokesperson would not comment on where Feaomoengalu's injuries came from.
The IPCA also investigated Feaomoengalu's claims of assault by police, but could not find evidence to substantiate them - saying there was no CCTV footage available from the arrest location to support Feaomoengalu's account.
However, the IPCA was also unable to prove where Feaomoengalu received his injuries, enveloping the incident in mystery.
Feaomoengalu was at The Bramble Bar in Onehunga with friends on Friday, March 8, 2019. Upon leaving the bar, Feaomoengalu entered into a verbal dispute with police officers who were attending a family harm incident nearby.
Feaomoengalu, a café catering assistant, claimed he had approached the officers' vehicle to take images on his phone of how it was parked across the road and footpath, before being told by officers to put his phone away and leave.
Catherine Crichton, Feaomoengalu's friend and witness to the scene, supported his account and, in a statement, said he was arrested after the situation escalated as officers tried to remove Feaomoengalu's phone.
Police claim officers found "an extremely intoxicated and agitated" Feaomoengalu having a verbal altercation with another man. When officers asked him to leave, police claim his aggressive behaviour continued and he was arrested for disorderly conduct after being warned multiple times.
Police also claimed Feaomoengalu made allegations that he had been assaulted in a bar earlier that evening. After an investigation, police found no evidence of this.
Feaomoengalu denied police's claim, saying he'd only had roughly four beers and was not extremely intoxicated, and had not been in an earlier fight.
A witness to the scene, who wished to remain anonymous, said he'd had concerns about Feaomoengalu's level of intoxication that night and described his actions as "antagonising police".
However, the witness did say it was not apparent Feaomoengalu had been assaulted prior to the incident with police.
A handcuffed Feaomoengalu was then transported by police car to the Auckland Police Station. On the way, Feaomoengalu alleges he was beaten and choked with a metal bar under his jaw by an officer travelling with him.
Police claim Feaomoengalu displayed "extremely erratic behaviour" during the ride, but could not detail how he got his injuries.
IPCA manager Griffyn Gully-Davies said officers denied using any kind of weapon against Feaomoengalu and they claimed Feaomoengalu's mood was unpredictable, varying from crying to yelling abuse.
Feaomoengalu was then taken to a police cell where he soon reported to officers that he couldn't breathe, coughing and vomiting blood.
A separate officer conversed with Feaomoengalu in Tongan, established he needed medical help and Feaomoengalu was taken to Auckland Hospital.
Gully-Davies said the IPCA determined Feaomoengalu was not taken to hospital immediately because officers claimed they had no indication he was injured.
She noted one possibility was Feaomoengalu's alleged assault earlier in the night could have been the source of his injuries, but weren't apparent until he was arrested. However, this was never proved and Feaomoengalu denied any claim he had been in an earlier fight.
At Auckland Hospital, Feaomoengalu was diagnosed with intoxication and concussion. A GP later diagnosed him with a concussion and chest bruises.
In her statement, Crichton said she was in disbelief when she saw Feaomoengalu's injuries.
"I am appalled at the obvious abuse or treatment he had been subjected to since he left me in the police car.
"On leaving me in Onehunga, he had not sustained any injuries nor was there any incident prior to his departure that would have caused these severe injuries."
Feaomoengalu said his children were shocked to see their father's condition the following morning.
"They were gutted, both my girls were crying, my little boy was crying when I told them it was from the police," he said.
"I told them that there are good police out there, but some are bad as well."
Feaomoengalu said the incident had eroded any trust he had in the police.
"I feel like they are people that I rely on to trust in and I end up not safe with them."
Feaomoengalu's boss Tava Feagaiga has worked with the 37-year-old for about three years and described him as a meticulous and hard-working guy.
"He's very friendly, he is good at what he does, he is a well-liked member of the team and gets on well with customers."
While describing Feaomoengalu as someone who speaks his mind, Feagaiga said there had been no issues with his conduct at work.
She saw no reason why Feaomoengalu would lie about what happened.
"He's is a straight shooter, I don't see why he would make a story up like that."