Police were justified in laying road spikes during a pursuit in which a vehicle lost control as the driver tried to avoid them, killing all three inside in a fiery crash.

The vehicle was being driven by 16-year-old Glen McAllister, while his brother, Craig, 13, was also in the car along with 13-year-old Brooklyn Taylor.

All three died at the scene.

The boys' Mazda and another Mazda appeared to be street racing as they were spotted travelling "closely together" in excess of 100km/h in the 60km/h zone at the intersection of Colombo and Brougham Sts in Christchurch about 11.10pm on January 13, last year.

Officers on duty that night followed the vehicles into Gasson St but then lost sight of them.

They then saw a male get into the back seat of a Mazda they could see, and immediately speed off.

Police engaged in a pursuit but abandoned it shortly after when the Mazda drove through a red light and continued to travel in excess of the speed limit.

Two other officers in the vicinity heard over the radio that the Mazda was heading towards them.

One of them deployed road spikes and as the Mazda travelled over them, it left the road and hit a tree. The fuel tank ruptured and the vehicle caught fire.

Police ran towards the vehicle, but due to the intensity of the fire, were unable to save them.

"The officer who laid the spikes conducted a sound risk assessment before deployment," Authority chairman Judge Colin Doherty said.

"His actions were proportionate to the threat the Mazda posed to the police and public. The Authority accepts that the officer had legal grounds to deploy spikes and is not responsible for this tragic outcome."

Canterbury District Commander Superintendent John Price said a police serious crash unit investigation found the car lost control as the driver attempted to avoid the spikes before running over them, a finding the Authority accepted.

Superintendent Price acknowledged the finding that officers did not adhere strictly to fleeing driver policy in using informal language to abandon the incident, and in leaving another member of the public inside a patrol car while laying spikes.

Additionally, one of the officers did not seek permission from the pursuit controller prior to deploying spikes.

"I am also satisfied that the officer considered whether to take the member of the public out of the vehicle as part of their risk assessment," Superintendent Price said.

"All officers involved have been reminded of the policy."

"We are equally focused on preventing harm and hurt in our community."

Under the fleeing driver policy, deployment of road spikes can be self-authorised if a risk assessment indicates an immediate response is justified.

"The incident was devastating to the families of the three boys who died needlessly, their friends and community, and the officers involved," he said.

"The weight of the badge on our shirts requires our people to be responsible for the safety of our community every day, and every day officers come in wanting to make the community safer.

"During these kinds of events our officers are constantly assessing and reassessing the risks involved, they take every decision very seriously.

"We need to balance the risk of taking action with the need to keep the public safe."

Price said police wanted everybody "to be safe and feel safe".

"That's exactly what our officers' purpose was on this night. No one could have foreseen the result.

"The officers' absolute desire and aim was to prevent harm on our roads and I absolutely support them."