A police officer who set his dog on a 14-year-old boy used an unjustified amount of force, the Independent Police Conduct Authority (IPCA) has ruled.
The incident occurred in October 2019, when the teenager was staying at a friend's house in Cambridge, Waikato.
The friend had taken his mother's car without her knowledge and the 14-year-old was driving the car. His friend was in the passenger seat, and there were four more youths in the backseat.
At around 1:30am, two officers who had attended a potential vehicle break-in nearby saw the youth driving the car, and thought he could have been involved in the break-in as he didn't match the registered owner of the vehicle.
They signalled for the driver to stop, and when he didn't they pursued him, reaching speeds of 150km/h in a 100km/h zone.
The chase ended when the driver entered a dead-end driveway. The teenager and his friend fled into the surrounding farmland, leaving the four backseat passengers to be caught almost immediately by police.
Shortly afterwards one of the officers pursuing the driver and his friend set his dog loose. The dog chased and bit the 14-year-old, seriously injuring his calf.
The teenager was given medical assistance at the scene and the police station before being taken to Waikato Hospital.
IPCA chair Judge Colin Doherty says the decision to try and stop the car, and then to chase when it failed to stop were justified - but the chase should have been stopped once the speed crept up.
"Insufficient consideration was given to abandoning the pursuit once the risks increased due to speed, the young person's manner of driving and the number of occupants in the vehicle."
However, using a police dog was "not justified or necessary" in the circumstances.
"While there was no issue with police using the dog to track him, the offending that he had possibly been involved in was not at a level that warranted a police dog being deployed to bite him," said Doherty.
Police acknowledge and accept the findings, saying they completed their own review into the use of the dog and the pursuit.
Waikato District Commander Superintendent Bruce Bird says police are often in "fast-moving and dynamic situations" that require an ongoing risk assessment.
"In this case police accept that the IPCA has found the use of a police dog was not appropriate in the circumstances."