The Independent Police Conduct Authority has identified multiple failures by officers as they restrained Alo Ngata, who died after he lost consciousness in the police cells in 2018.
The 29-year-old had violently assaulted a stranger in Auckland's Freeman's Bay, and strongly resisted arrest.
He was tasered four times, pepper sprayed twice and restrained with handcuffs, leg restraints and a spit hood.
In its report, released today, the IPCA found that the spit hood was incorrectly applied so that it covered Ngata's entire face.
As a result, officers were unable to see that he might have been having difficulty breathing.
He died in Auckland Hospital two days later.
Superintendent Karyn Malthus, the Auckland City commander, said the circumstances were extraordinary and the death tragic.
She said police accept officers didn't constantly monitor Ngata, after he was left in the cell with the spithood on.
An internal investigation found no grounds for a criminal prosecution against any of the officers or any employment proceedings.
The death is before the coroner.