A technical glitch meant the officer involved in a fatal pursuit did not hear initial orders to abandon the chase, Canterbury District police commander Superintendent Gary Knowles says.
The Independent Police Conduct Authority (IPCA) has ruled an officer should have abandoned a pursuit which ended with a 15-year-old passenger being killed.
Early last year, Fabian Mika was carrying three passengers in a stolen Hilux when he tore past an officer.
The officer signalled Mika to stop, but he sped off reaching speeds of 90km/hour in a 50 km/h zone.
Mika then drove on the wrong side of the road for almost 2km and the officer followed despite being told to abandon the pursuit twice.
After a 9km pursuit Mika crashed killing a passenger and injuring the two others.
The authority said the officer complied with pursuit policy in the initial stages of the chase but should have abandoned it when Mika drove on the wrong side of the road.
The police officer was twice told to abandon pursuit but he did not hear the order. However, after hearing the third order, he stopped, it said.
Mr Knowles told Checkpoint a technical hitch was behind the officer not hearing the order the first two times.
Listen to Gary Knowles
"That was just a technical glitch and that can happen from time to time. You've got to bear in mind that these are extremely high pressure, challenging situations and we take time seriously," he said.
"But this was a sole officer in a vehicle. He was having to put all those factors before him. I honestly can say, having spoken to him, he didn't hear the first two instructions to abandon."
Mr Knowles agreed the pursuit should have been abandoned but said the events must be put into context.
"The officer involved knew that Mr Mika had been involved earlier in the day in an alleged aggravated robbery with a firearm," he said.
"He knew Mika's criminal history in the fact that he was a Mongrel Mob member. He had to assess what the risk was in letting him flee.
"He had to look at all those factors and come to the conclusion that the pursuit in his mind - and I support him - was justified."
Fleeing driver incidents were among the most challenging tasks police faced as they were fast-moving, unpredictable, high-pressure situations, Mr Knowles said.