A former policeman says mistakes in the way an armed killer was let off with a warning hours before he fatally attacked a former Whanganui woman were linked to her death.
However, an official report into police handling of the case disagrees.
Police were this week criticised, but cleared, over their handling of Tevita Filo, who killed Jo Pert in Auckland in January 2016.
The Independent Police Conduct Authority said officers should have made more inquiries when dealing with Filo the day before he killed Ms Pert, who was born in Whanganui and has family in Castlecliff.
They also found a police dispatcher did not pass on all the available information.
A former policeman and close friend of Ms Pert, who laid the complaint over the way police dealt with Filo, has slammed the authority's findings as "unbelievable" and "contradictory".
He and Ms Pert's family believe if Filo had been arrested the night before, he would not have been free to roam the city's streets the next day and harm her.
Ms Pert, a mother-of-two, was killed in Shore Rd, Auckland, as she went for a morning jog. Her funeral was held at Raetihi.
The authority said it was not possible to draw any link between her death and police actions the day before, when a motorist called 111 to say he had been followed from St Heliers to Howick.
Within minutes, two officers stopped Filo and spoke to him at the roadside.
They said Filo was acting strange and also noticed a knife in his car.
Meanwhile, the police dispatcher checked Filo's car and found it was wanted after a theft from a shop.
However, she did not recall seeing that information and did not pass it on to the officers. Nor did she pass on further information about Filo's disturbing behaviour the motorist had reported.
The officers seized the knife and warned Filo. He denied he had been following anyone, and the officers accepted his explanations for his actions.
The authority said Filo's behaviour and possession of the knife should have prompted the officers to make further inquiries with the dispatcher before deciding what to do.
"[That] would have led them to interrogate Mr Filo about the reasons for his actions. In the absence of a more plausible explanation, they might have arrested him and taken him to the station," said authority chairman Judge Colin Doherty.
The former policeman said it was hard not to conclude that police shortcomings contributed to Ms Pert's death.
"Had the attending officers been supplied all the information, I'm of the belief that they would have undoubtedly arrested Filo that night and therefore it is very unlikely he would have killed Jo the next morning because he would have been locked up."
He said the fact attending officers found Filo acting in a strange and agitated manner coupled with finding a knife should have been enough to take him in for questioning.
"When combined with the other mistakes the IPCA have found, his arrest should have been a no-brainer.
"The final conclusion from the IPCA completely contradicts their findings. The findings warrant a review of police procedures so that this cannot happen again."
He said he was compelled to lay the complaint for Ms Pert, who was a close and longtime friend.
"Jo was such a caring person - if the shoe was on the other foot she would be beside herself and she would have asked exactly the same questions."
He was now considering appealing the decision and eager to hear the coroner's findings.
Justice Murray Gilbert found Filo not guilty by reason of insanity for Ms Pert's murder and of 12 other alleged crimes in the 17 hours before and after her death, because he was incapable of understanding his actions were morally wrong due to his schizophrenia.