Police have refused to release an investigation file into an allegation that an officer threw a heavily pregnant woman to the ground during an arrest and bruised her face.
The woman complained to the Independent Police Conduct Authority, which passed the investigation to the police while the IPCA oversaw the process, which it was satisfied with.
A police investigation found the use of force against the woman was appropriate and justified, but they did admit the officer could have done things differently and that it was "distressing" for the woman.
It said the IPCA agreed with their finding.
The IPCA asked that the incident be looked at as a potential criminal matter.
"The conduct of the officer involved did not meet the threshold for criminality liability, but they did find that some lessons could be learned from the episode," the IPCA statement said.
The incident, in Hamilton on 16 June 2018, alleged that the officer used excessive force on a heavily pregnant woman.
Police found the officer used the right amount of force to restrain her given she was repeatedly kicking the officer's legs while under arrest.
The officer said he tried to guide and support the woman when taking her to the ground.
Under the Official Information Act, RNZ requested the investigation file into the incident, which was declined in its entirety by the police under section 9(2)(a) - to protect the privacy of individuals.
Police did not provide any information from the investigation file whatsoever.
In a statement, the police acknowledged the findings and reiterated that the use of force was justified.
"The police found the officer's use of force during the arrest was justified as the complainant was repeatedly kicking the officer," a spokesperson said.
"Frontline policing is a dynamic, unpredictable and occasionally volatile environment, where Police are required to make quick decisions to ensure the safety of all involved."
The IPCA said it received a complaint from the woman involved in the incident.
"This means that the incident was not investigated directly by the Authority, but instead we discussed the issues raised by the incident with Police and reviewed the progress of their investigation as it proceeded. We also reviewed the final findings of their investigation, and discussed with Police what the impact of these findings meant."
The IPCA asked the police to look at whether the incident was a criminal matter, and an employment one.
"The Authority is of the view that the Police investigation progressed appropriately, with a sufficiently experienced officer appointed to lead the investigation, and that investigating officer seeking appropriate evidence as part of their inquiry (including seeking evidence from all identified witnesses to the event).
"Police found that, on balance, the weight of evidence meant the conduct of the officer involved did not meet the threshold for criminality liability, but they did find that some lessons could be learned from the episode, and this was addressed with both the officer involved and on a wider scale with lessons learned being recorded in central police systems."
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