A damning report says police could have saved the life of a woman who was bludgeoned to death by a mental health patient.
A litany of mistakes are outlined in an Independent Police Conduct Authority investigation which says police had the information and the ability to prevent the murder.
Convicted killer Christine Morris had threatened to kill White, 53, before she escaped from a Waikato mental health unit.
White's partner Gary Chadderton says the report does not give him closure and he cannot get the tragedy out of his mind.
"She's with me every hour of the day," Chadderton said.
The police visited Chadderton this morning to personally apologise for their failings.
"It's all very well to come round to me and say how sorry you are and the rest of it, but it was bloody preventable," Chadderton said.
The report said on the morning of the attack in January 2010 police had been notified by fax and telephone that Morris - a 40-year-old profoundly deaf patient at the Henry Rongomau Bennett Centre in Hamilton with a serious mental health illness - was missing after climbing a fence.
However, the fax was not received by police until an hour after it was sent because their fax machine had been switched off. Telephone messages had also not been diverted.
Eventually a nurse at the facility called 111, more than an hour after Morris had escaped.
Two officers went to Morris' house but could not find her. White was mowing her lawn next door and the officers told her to phone them if she saw her neighbour.
A short time later, at 11.30am, the police communications centre received another 111 call from a nurse at the mental health facility after a neighbour rang her to report that Morris was at White's house and making threats.
However, police did not send any officers because they thought it was a repeat of information from an earlier call from the nurse.
Around 50 minutes after that call, the neighbour rang 111 to say Morris was leaving White's house with blood on her face.
Police were then dispatched and found White dead.
Former Waikato police area commander Allan Boreham - who was in charge of the region at the time of White's death - today admitted police failed her and says it is "incredibly disappointing".
"We had the information and ability to do it and we didn't and there is nothing more saddening than that," Assistant Commissioner Boreham said.
"Police clearly failed Diane when she needed us after several individual errors came together on the day that resulted in a situation that had tragic consequences.
"We are deeply sorry for what happened and I've met with her family in person to tell them this. I've also told them about a range of things we've done in the three years since to prevent a similar situation happening again."
The authority said inadequate handling of the 1-1-1- calls and a failure to deal with Morris' mental health issues were also to blame.
"We are doing everything in the memory of Diane to make sure this never happens again," Boreham says.
The Waikato District Health Board also passed on its condolences to White's family today and said it could have done things differently, "knowing now what we know about the defendant's state of mind."
"We have spoken to the staff involved about some of those things but no one acted negligently or unprofessionally and no one person could reasonably be held responsible," the DHB said in a statement.
It also clarified how Morris was able to escape the facility:
"Staff made a reasonable judgement to allow Ms Morris to have a cigarette in the courtyard to cool down. While in the courtyard, she scaled the fence and staff were unable to stop her. They then contacted the police as described in the authority's report."
Boreham says responding to incidents involving people with mental health issues is often a very complex and challenging area for police officers.
The Ministry of Health and police finalised a Memorandum of Understanding last year that better defines responsibilities and processes to be followed when dealing with incidents involving mental health patients.
Police have also upgraded its policy on people with mental impairments, which sets out steps for returning mental health patients who are reported missing
sentenced to life in prison at the High Court in Hamilton last
year, after earlier pleading guilty to White's murder.