The Independent Police Conduct Authority has found police used reasonable force on a man who became unconscious while they restrained him.
The man was taken into custody at Christchurch's Justice and Emergency Services Precinct on 24 November last year due to appear in court the next day.
He defecated on his cell bed and attempted to eat a food container and plastic utensils.
The next day the man who had a history of mental illness, substance abuse and violence assaulted an officer.
Staff were attempting to take the man out of his cell to take him to prison when they used a shield to restrain him, put him on the ground and placed a waist restraint on him.
While on the ground the man lost consciousness and was taken to hospital.
The IPCA found the use of the shield was reasonable but the restraint procedure was poorly executed.
IPCA chairperson Judge Colin Doherty said "Having interviewed witnesses and reviewed the footage of the man being restrained on the ground, the officers' use of force was reasonable under the circumstances.
"There is no obvious indication any officer restrained the man in a which would cause him to struggle to breathe."
The IPCA found the man's cell remained unclean for several hours after he defecated and said officers should not have left the man in soiled clothing.
It recommended police, Corrections and Ministry of Justice work to clarify at which point each agency is responsible for remand prisoners in the custody suite.