Police withheld an internal review which would have shown a coroner that they had failed to properly investigate the intense relationship between a male teacher and a 13-year-old girl who later committed suicide.
An internal police report, obtained by the Weekend Herald, strongly criticised the investigation, saying leads were not followed, information was missing and there were exceptions to police procedure.
The report was available in time for the 2016 inquest into Reiha's death but police did not give it to Coroner Carla na Nagara.
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Na Nagara produced findings which praised the quality of the inquiry carried out by the sole trainee detective left to investigate the girl's intense relationship with Back, who is now banned from teaching.
The Herald obtained the internal police inquiry through the Official Information Act and found it showed police a month before the inquest began that its investigation had significant flaws.
Police have defended withholding the report, saying they did not want to influence the Coroner when she had a wider base of information available from which to form conclusions.
Reiha's parents, Bruce and Hinemoa McLelland, discovered her relationship with Back
in April 2014 and reported it to police, who found Reiha and Back had exchanged about 4000 text messages over the previous three months, and emails back to September 2013.
The police investigation and inquest produced no evidence the relationship was sexual, and Reiha and Back always denied it was physical. Reiha's enforced separation from Back during and after the investigation - later likened to the impact of a "divorce" - was followed by her suicide in August 2014.
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The inquest into Reiha's death heard evidence from September 2016 through to December 2016 and led na Nagara recommending changes to mental health processes and tightening of a law around hiring those working with children.
The police investigation of Back was an inquest focused on whether there were gaps which, if addressed, might "reduce the chances of future deaths in similar circumstances".
In her findings, na Nagara commended Detective Richard Downes for the police inquiry, saying "he ran an appropriate, competent and effective investigation and no substantive failings with that investigation were identified in cross-examination".
The finding is contrary to that from police national child protection coordinator Detective Sergeant Natasha Allan, who carried out the internal inquiry before the inquest and told senior officers the original investigation was incomplete.
She detailed leads not followed, missing information and exceptions to police procedure through the investigation.
"In my view there was a lack of supervisory oversight and guidance throughout the investigation."
It was an issue Moira Macnab, the lawyer hired by Reiha's family, attempted to raise during her cross-examination of Downes during the inquest while trying to understand who was overseeing the trainee detective's investigation.
She was interrupted by the police's lawyer Steve Manning, who asked: "Is this really helping? The witness has answered the question. This is a theoretical administrative matters that this witness has said. He's given his answer and we're just bagging away on it."
A subsequent review by the Independent Police Conduct Authority after the inquest had the benefit of seeing the 2016 internal review and concluded police policy on supervision of inquiries had not been followed.
The police internal review by Allan identified a number of deficiencies in the case. The only people identified as potential witnesses included Reiha's parents, Bruce and Hinemoa McLelland, and yet there was no record of statements being taken from either. There were also no notebook entries or police job sheets concerning the parents and the only record of contact was in the police computer system.
Allan said statements should have been taken from a friend of Reiha's who was said to have spoken to Back about concerns. Others who should have been interviewed included a nurse at the mental health unit who raised concerns leading to CYF being notified and another nurse who said she saw Reiha sitting on Back's knee at the hospital.
Allan said there should also have been a statement taken from Angie Mepham, Back's partner, which the original investigation plan had said was "not required". She said questions should also have been asked as to why Reiha called Back "Big Boy" in
communication. Evidence gained later at the inquest from Back said it was a nickname many people used for him.
Other deficiencies included the absence of notebook entries or a job sheet from Downes' interview with Back, and a lack of a report from a police interviewer's attempted to interview Reiha.
The police investigation into Back's relationship with Reiha finished in mid-June and an assessment of the evidence was sent to police managers in late July saying the inquiry did not sustain grooming or other charges.
The findings from na Nagara referred to Downes' investigation as "comprehensive" and found "no evidence of a sexual relationship or sexual grooming on the part of Mr Back".
"No new evidence has subsequently emerged that calls into question the validity of this conclusion," she wrote.
Allan's internal inquiry said there was "no doubt that inquiries completed by police did not establish evidence of criminal offending against Reiha".
However, she said the nature of the relationship, and "intimate correspondence", meant "there was a strong likelihood that there was more to this friendship".
She said an interview by police with Reiha, during which she hardly spoke, and the lack of supporting evidence, meant police had "an obligation to thoroughly investigate this case following all lines of inquiry".
Allan said this was necessary in case Reiha had later made a further statement and "to prevent further offending".
The internal report said the inquiry was prompted by media reporting of a conflict of interest held by former Detective Sergeant Theo Ackroyd, who signed off Downes' investigation report while also chairman of the Gisborne Intermediate board of trustees. Ackroyd has since left the police.
In a statement, Detective Superintendent Chris Page said the internal inquiry was provided to the police lawyer at the inquest, Steve Manning, in August 2016
"He was advised the report was confidential as it was being used in support the ongoing employment investigation into the actions of DS Ackroyd and possible review by the Independent Police Conduct Authority (IPCA)."
Page said the Coroner was made aware of the existence of the internal inquiry in February and March of 2017.
By then, the inquest had finished hearing evidence and na Nagara was in the process of writing her findings.
Page said the internal review did not review Reiha's diaries or about 4000 text messages exchanged between Back and Reiha. Witnesses were also not interviewed, he said.
"Far more factual evidence was provided to the Coroner for the purposes of the Coronial hearings."
He said it was "inappropriate to disclose the report" when it was produced for internal reasons and hadn't considered the wider evidence.
It was the view of police "the Coroner was able to draw her own inferences from all evidence available", including testimony from Ackroyd and Downes during the inquest.
Page said police had met with the McLelland family after the release of the IPCA report and acknowledged "the investigation could have been better".
Manning would not comment on the report or related issues, referring the Herald to police.
The McLelland family would not comment on the internal inquiry but Macnab - the family's lawyer - confirmed neither she or Reiha's parents had seen it until the Herald provided a copy.
"I would have liked to have seen it before the inquest. It definitely should have been made available."
Macnab said an inquest was intended to be a forum in which all parties involved disclosed any relevant information to understand the causes behind a death and to find whether steps could be taken in future to avoid a similar circumstance.
"If the Coroner had this report, she might have had slightly different findings."
Coroner Carla na Nagara told the Herald she had no power to re-open the inquiry. In a statement, she said: "Should family wish for a case to be re-opened, they would need to apply to the Solicitor-General."
A request for comment has been passed to Ackroyd through the NZ Police Association. He has yet to respond.
Where you can get help:
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