Judge Ian Binnie identified some highly significant mistakes made by the police which compromised the integrity of their investigation into the killings at Every Street. These are covered in pages 155 to 192 of his report into David’s claim for compensation.  Binnie quoted from the Privy Council on the poor police performance:

“Too much that the Police ought to have done was left undone and, of even greater concern, too much of what they did discover was not provided to the jury and thereby the jury was misled” (para 486).

Ian Binnie summarised his conclusions as follows:

“Having regard to the terms of the Cabinet’s ‘extraordinary circumstances discretion’ set out in the Minister’s letter to me of November 10, 2011, it is my opinion that the egregious errors of the Dunedin Police that led directly to the wrongful conviction make it in the interest of justice that compensation be paid” (para 27).

Summary of most egregious mistakes made by police (more detail below):

1) They failed to investigate Robin Bain’s mental health & allegations of incest: the police failed to follow up on concerns about Robin Bain’s mental health or on Dean Cottle’s allegations of incest by Robin Bain. This meant they failed to investigate a potential motive for Robin Bain to have killed his family and then committed suicide.

2) They destroyed evidence: the police allowed the house where the killings occurred to be burnt down three weeks after the deaths. This meant crucial evidence, including the bloody sock prints of the killer, was destroyed. Police also ordered the destruction of additional evidence about 12 months after the trial.

3) They misled the jury:  
a)  the Police armourer gave inaccurate evidence at the 1995 trial about the length of the rifle  – he over-measured it by about 20 cms casting considerable doubt on whether Robin Bain could have shot himself.

b) Police failed to take gunshot residue tests of either Robin’s or David’s hands and arms in the time period required.

c) The police told the jury the spectacles found on the floor belonged to David although their expert witness said they belonged to David’s mother. Police also gave inaccurate information about where the left lens of the spectacles was found;

d) The police gave the jury a definitive time about when the family computer was switched on when the evidence did not support this;

e) Police failed to tell the jury they had checked a key witness’s clock confirming the time David returned to the house after his paper run.

1) Failure to investigate allegations of incest

The most egregious mistake, with devastating consequences, was the police failure to follow-up on allegations that Robin Bain was having mental health problems and related allegations made by Dean Cottle that Laniet was being sexually abused by her father. Prior to arresting David, the police were well aware that Robin Bain had been under stress and was potentially unstable. They knew about the marital discord between David’s parents and “the curious activities at the school over which Robin Bain presided”. But they eliminated Robin Bain as a possible suspect two days into their investigation.

Even after Cottle made his allegations of sexual abuse, the police refused to investigate this issue any further.  As a result, the judge’s decision to reject Cottle’s testimony as unreliable was almost inevitable – because there was no corroborating evidence. The problem was the police never bothered to look for any.   On the witness stand, senior detective Sgt Doyle said the police did not investigate allegations of sexual abuse against David’s father was because “this was a homicide investigation, not an incest investigation” (para 538).

Judge Binnie criticised the police for this failure. He wrote:

The lack of interest in a possible motive for Robin is all the more surprising as the Police never did uncover a motive for David Bain other than a minor disagreement with Robin on 19 June (the day before the killings) as to whether Robin would take the family chainsaw to Taieri. This is hardly a plausible motive for David Bain to kill five people in the absence of evidence (of which there was none) of a serious mental disorder” (para 539).

2) The destruction of evidence by police

The house was burnt down:  The killings in the Bain house at Every St, Dunedin occurred on 20 June 1994. Seventeen days later (on 7 July), at the request of extended family members, the New Zealand fire service burnt the house to the ground.  Although it was an active crime scene from which evidence was still being gathered, the Dunedin police agreed to this  act of arson. This was an extraordinary decision in breach of basic police protocols about the preservation of evidence. Perhaps the most valuable item destroyed was the piece of carpet containing the bloody luminol footprints of the killer.

Police Detective Sgt Weir was supposed to supervise ESR  scientist, Peter Hentschel when he visited the crime scene on June 21 – when they jointly performed the “luminol” footprint investigation. Based on Mr Hentschel’s measurements, the prosecution claimed that a 280mm-long bloodied sock print found outside the mother’s bedroom was made by David. This formed part of the evidentiary basis on which the conviction was obtained that put David in jail for 13 years.

Although some sections of carpet from elsewhere in the house were kept, this piece of carpet – from which the crucial foot measurements were made – was not.  The carpet, along with other evidence that may have been helpful, went up in flames. The result was that only the ESR experts, working for the Crown, had an opportunity to inspect this crucial piece of evidence.  Because the defence never had the chance to have the luminol carpet examined by their own scientists, Mr Hentschel’s statements were accepted as accurate at the trial by all concerned, including the defence.

After the trial, David’s bare foot was measured at 300 mm which showed his feet were too big to have made the print. The print actually fitted Robin whose his bare feet measured 270mm – but the jury was never told this. Ian Binnie wrote:

The practical (and unfortunate) result of this failure to preserve the carpet … is that no other expert can reassess the correctness of Mr Hentschel’s original 280 mm measurements on which all the other expert testimony regarding these prints must now depend (para 245).

Other evidence lost or destroyed by police after the first trial.

a) Failure to protect evidence: Det. Sgt Lodge was responsible for protecting evidence from Robin’s body. He was criticised for failing to preserve evidence of firearms residue on Robin Bain’s hands and failing to preserve the skin sample surrounding Robin’s gunshot wound.  This unleashed a significant “debate among the experts about whether the fatal shot was close, intermediate or distant (para 558).”

Laniet’s diaries and letters written to her mother were destroyed. David’s lawyer, Mr Reed said at the retrial the diaries could have contained allegations of the sexual molestation. The computer with the “sorry” message, which also may have contained relevant information, was not preserved.  After the first trial it was returned to extended Bain family members who left it under a house. 

b) Deliberate destruction of evidence: Some evidence was actually destroyed on instructions from Detective Senior Sgt James Doyle, the officer who was second in charge of the case in 1994. This included scrapings from underneath Robin Bain’s fingernails, a smear of blood on Robin Bain’s left hand and skin samples from Robin Bain’s hands. These scrapings may have contained DNA from the victims as they struggled with the killer, which, if so, would have suggested that Robin was the killer.

The Police never even had these scrapings analysed and then they destroyed them after the trial. The destruction went ahead even though Bain’s previous lawyers threatened the police with a High Court injunction if they considered destroying any of the evidence – because if the fingernail samples were from any of the murdered children, this would have helped David prove he was innocent.

The authorisation to destroy the samples was given by Det Sgt Doyle on 22 December, 1995 and carried out on January 26, 1996. Ian Binnie was highly critical of this police decision. He wrote :

Det. Sr Sgt Doyle was aware of the Police obligation to preserve evidence (whether or not it had been filed as an exhibit at trial) until all appeals were exhausted, but he nevertheless ordered the destruction of all such material to be completed by 26 January 1996 despite the possibility of a further appeal to the Privy Council, and without consulting defence counsel. His only explanation was that in his experience such appeals were rare (para 525).

c) Failure to document photos accurately: The hundreds of photographs taken by police were poorly organised and undocumented. In the investigative work done by David’s defence team subsequent to the 1995 trial, it was often difficult to establish when any of the photographs were taken. The Police photographer who edited the crime scene photos said he had no recollection of doing so. Even worse, the video camera he used was equipped with a date and time function but the photographer either forgot, or didn’t know how to turn it on.

The Police also failed to show the jury any of the “mortuary photographs” taken by the pathologist, Dr Dempster, which showed details of Robin’s injuries – because they forgot to ask for them. These photos were finally shown to the jury at the retrial in 2009.