The Independent Police Conduct Authority has cleared officers involved in two pursuits of that killed three teenagers.
Eden Nathan, 16, was a passenger in a stolen car driven by Kara Kauri, 15, who took police on a high-speed chase through Auckland early on January 24.
She died after Kauri lost control and crashed into a vehicle coming the other way.
Kauri has not been spoken to by police as she remains in a coma.
Neither were wearing seatbelts.
The second chase, on Queen St in Masterton, claimed the lives of 15-year-olds Pacer Willacy-Scott and Hoani Korewa on January 31, this year.
The pair died after the driver of the vehicle lost control and crashed into a lamp post in a short pursuit with police.
A 14-year-old was later charged with driving offences. At his sentencing in July, it was revealed the teen had admitted smoking half a joint the night before. He was sentenced to six months' supervision at a CYF residence, with the possibility of early release in November if certain conditions were met.
In the pursuit that killed Nathan, the Authority said the officer twice reached 115kph in a 50kph zone.
It acknowledged the speed was high, and would be unjustified if it had continued for any length of time.
"On both occasions, it was reached for a very short time before Officer A slowed significantly to navigate a bend in the road and to travel through a red light. In addition, at the time the high speeds were reached, the other risk factors were low: there was little traffic on the road, the manner of driving was 'fine', the weather was clear and there was good visibility and road conditions. For these reasons, the authority finds the speeds reached by Officer A were justified in the circumstances."
The Masterton chase was only 30 seconds long, the authority found, too short for officers to tell the communication centre any relevant risk factors.
"However, when the Honda went through a compulsory stop sign "in excess of 100kph" in a 50kph zone, Officer A determined that the manner of driving was too dangerous and he notified CentComms that he was abandoning the pursuit."
The vehicle crashed shortly afterwards and was witnessed by the officer.
The authority found that police "complied with law and police policy, in so far as they were able, during the short pursuit".
The pursuit continued for four minutes as Officer A reiterated to NorthComms that there was no traffic on the road and the conditions were dry.
The speed varied between 60km/h and 115km/h. As the vehicle turned onto Buckland Rd, the front seat passenger began throwing clothing out of the window, forcing the officer to slow down.
After driving about 500m, the driver of the Nissan speeded up. Officer A radioed NorthComms advising, "they've picked up their speed, they're still throwing crap out of the car, it's 115 over 50 [and] they're approaching a red light with Massey Rd".
Officer A also said there was no traffic on the road and he was about 300m behind the Nissan.
Officer A told NorthComms that the driver of the Nissan did not slow for the red light and was pulling away from him. Officer A slowed as he approached the intersection and after ensuring that there was no traffic, continued through the red light.
By now he was only able to see the Nissan's tail lights in the distance.
Shortly after, Officer A advised NorthComms that the Nissan had gone through a second set of red traffic lights, at Ashley Ave.
After slowing at the second set of traffic lights, the officer lost sight of the Nissan as it rounded a left-hand bend on Buckland Rd.
Within seconds of losing sight of the Nissan, Officer A said he drove around the bend and saw that the Nissan had lost control and collided with a Toyota Prado travelling in the opposite direction.
At 3.37am, Officer A told NorthComms there had been "a major crash" and police units would be required. An ambulance arrived at 3.53am.
The chase had started after Officer A was sent to Hill Rd following a report of a Nissan being broken into. Two cars were reportedly involved in the theft.
On arrival, he saw two cars matching the description and followed the Nissan, which had driven off at speed.
Police started chasing the vehicle in Masterton "purely because of its manner of driving".
The officers said they saw the car swerve across the road, crossing the centre line. Their speed radar recorded the car travelling at 65km/h in a 50km/h zone.
When the car suddenly turned into Harlequin St, the officers saw it was a red Honda Civic that matched the description of a car that had been stolen earlier that evening.
When the driver failed to stop and tried to evade police, the officers were justified under the police fleeing driver policy to commence a pursuit, the report noted.
Because the chase happened at 2pm and was in the centre of town, several witnesses were interviewed.
One said they heard the "revs of a vehicle engine" and then saw the red car "screaming up the road pretty quickly [going] straight through the intersection".
Several witnesses said it did not appear to slow down as it crossed a series of raised courtesy crossings, and sparks flew out from underneath it.
The police car then "seemed to stop following it", a witness said.
As the car hit the last courtesy crossing, a witness recalled it "totally lost control, it hit the ground and just completely spun out".
A police crash investigator determined that the Honda was travelling on Queen St at an average speed of 120km/h.
The Honda lost control on the fifth raised courtesy crossing, and swerved left into a concrete lamp post.
National road policing manager, Superintendent Steve Greally, said "both outcomes could have been avoided had each driver stopped when requested to by police".
"There is no infringement notice or conviction that is worth the loss of lives."
"We must also remember the impact these tragedies have on families, friends and the wider community.
"Fleeing driver situations are often complex and require our staff to make difficult decisions in rapidly evolving circumstances."