The police watchdog has ruled an officer should not have set his dog on a woman hiding in a bush.
The woman had been a passenger in a car that failed to stop for police. The bite left her with life-long injuries.
In a decision released today, the Independent Police Conduct Authority (IPCA) said two officers followed a car that had been driven dangerously to a rural Foxton property last October.
They found the car empty but saw two figures ahead of them. The dog handler called out, telling the pair to give themselves up.
When they refused, he released his dog.
The dog bit the woman on her lower leg, leaving her with serious injuries. She was arrested and the male driver gave himself up after being tracked into a neighbouring paddock. An ambulance picked the woman up from the Palmerston North Police Station and she was admitted to hospital, where she was operated on.
The IPCA concluded the use of the dog was out of proportion to the situation. The woman had committed no offence beyond being on a property without reasonable excuse - for which she had a valid defence, it said.
The authority noted a local police review had supported the dog handler's actions, but Judge Kenneth Johnston said the young woman was suffering the life-long consequences of his "poor decision".
"Officers need to consider carefully whether the injury that may be caused by a dog is proportionate to the offence the person is suspected of having committed. Not immediately surrendering to police does not on its own mean that an officer is justified in releasing a dog."
The dog should have only been used to track the parties, rather than restrain them, the IPCA said.
The police had accepted the decision, despite their earlier support for the officer's actions.
They said the woman was not in the sight of the dog when it was released, as per police policy, and it was risky to let the dog loose when they did not know if the woman was the driver.
Central District Commander Superintendent Scott Fraser said situations like this were typically fast-moving, and officers needed to consider a range of critical information quickly.
"We back and train our staff to make the best possible decisions in the moment, in what is often a split-second," he said.
"However, occasionally the decisions we make can have unfortunate impacts like in this incident, where someone who was not a significant offender or risk is badly injured."