The grieving partner of an innocent man shot by police on Auckland's Northwestern Motorway is furious the officer won't be charged, saying she hopes he is haunted by her dead partner.

Stephanie Cook and her family have questioned why the officer who fired the fatal bullet won't face a judge and jury, like anyone else.

They say it reeks of police protecting their own.

"I hate him for what he did - my daughter will grow up without a father," said Cook, the fiancee of slain courier van driver Halatau Naitoko.

Seventeen-year-old Naitoko died after he was caught in the crossfire between police and alleged gunman Stephen McDonald in January.

Cook said the officer should be charged and face court like anyone else. "If I was running around with a gun and shot somebody by accident, surely I would be behind bars already."

She did not accept police were acting within their duties, or in self-defence. In any case, it should be up to a court to decide that, not police.

Cook wants to see the police report and meet the officer who fired the fatal bullet to hear an apology. "The least he can do is meet us and let us know who he is."

She said she would question him on the circumstances of the fatal shot "and how he could miss [the offender] ... being a trained police officer and all.

"I hope Hala is haunting him."

On Thursday, Auckland city district police commander Superintendent George Fraser said the decision not to charge anyone came at the end of a thorough police inquiry.

"The recommendations of the homicide investigation team were made in conjunction with advice from the police senior legal adviser and which were peer reviewed by independent senior legal counsel, John Haigh, QC."

But Cook's mother, Dorothy, said it was a case of "police protecting each other".

"I mean, what makes him different? Is it going to be like that all the time when situations like this occur and innocent people die? The public have the right to know because it could be someone else's son."

She was critical of police announcing the decision on the same day as the Budget, when media were focused on political matters. Polcie said yesterday this was "coincidental".

The family is also angry with Police Minister Judith Collins and Prime Minister John Key who had extended sympathies in January and promised thorough inquiries. "He [Key] promised justice and there is nothing," said Stephanie Cook.

Collins said yesterday that it would be inappropriate to comment on the police findings.

Cook said the couple's daughter, Hemo Naitoko, now 2, asked for her father constantly. "Just today she was crying for her daddy. I have this photo of Hala on my phone that she loves. Then the light turned off and it went black and Hemo said 'Mummy, mummy, where's daddy gone?' Every time Hemo sees a white van like the courier van Hala used to drive she would say 'Daddy!'."

She said police had not spoken to her and had found out about the police decision from other family members.

"I was just crying and crying because there is no justice. The facts are there. He was shot by a cop. What more is there to it?"

McDonald, the man who allegedly sparked the police chase and AOS callout, has been charged with 35 offences. An Independent Police Conduct Authority investigation and separate coroner's inquiry are continuing into the case.

Auckland University associate law professor Bill Hodge said a prosecution could have come about depending on whether police had been reckless.

However, in this case, lives were in danger.

"It's one of those rare situations in New Zealand that deadly force was justified," he said. "The deadly force was legitimate to this deadly target. In this case the target was a great threat."

Hodge said it was important that the police not be deterred in carrying out their duties in such circumstances. "We don't want to deter those who are entrusted with the extraordinarily public responsibility of using deadly force in these situations.

"We need to protect them from being deterred and petrified of legal consequences."

Hodge said the circumstances were different than deaths that occur during hunting accidents - those deaths usually happened when a person had been wrongly identified as a target.

"The target was valid, it's sheer bad luck the wrong person was killed."

Hodge was perplexed as to why the report was not being made public, or at least given to Naitoko's family.

"I would think in the interests of justice being done the family should have it, you should have it, and I would like to see it."