Police subjected a woman to unnecessary and excessive force and left her to sit in a restraint chair with no trousers on, the Independent Police Conduct Authority has found.
The IPCA investigation found officers did not adequately provide the level of care needed for the woman who had a history of mental health issues and self-harming.
They were found to have used unnecessary and excessive force on the woman who was in custody in Tauranga in 2019.
She was arrested for fighting on 21 June 2019, and was placed in the back of a patrol car, where she struggled with officers. She was punched in the cheek by an officer after she attempted to bite him, and was placed in a spithood.
The IPCA found that the spithood was justifiable.
Officers failed to enter her details into the police database, and as such, were unaware of her mental health issues, and history of self-harming.
While in custody, she attempted to self-harm twice. Following both reports, the IPCA found officers applied significant physical force to restrain the woman, and was placed in a restraint chair.
The IPCA said the woman should have been put in a tear-resistant gown, and officers should not have left her sitting in the restraint chair with no trousers on.
She was taken to hospital where she was found to have a fractured wrist, but the IPCA could not determine what caused this.
"Ms X was a vulnerable person who was in need of proper care," Chair of the IPCA, Judge Colin Doherty said.
"The failure to properly assess her and check police records, meant she was put at risk by having access to the means to harm herself which itself led to unnecessary uses of force."
Police accepted the findings and conceded that officers did not provide the level of care required.
"The issues highlighted in the report have been raised with the staff involved and the need to adhere to policies in place has been reinforced," Bay of Plenty District Commander Superintendent Andy McGregor said in a statement.
"Earlier this year, police commenced a national custody programme to deliver an effective, safe and transparent custodial service that all stakeholders can have trust and confidence in.
"The findings from this IPCA report will feed into that ongoing work programme."