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Assistant Police Commissioner Malcolm Burgess said the theory that Robin Bain's fingers were marked by a gun was interesting, but was not new evidence.
He said police today examined Mr Bain's fingerprints that were taken after his death, which showed "an absence of fingerprint markings in the same place on his right thumb as the dark marks appearing in the photograph''.
"Our fingerprint experts advise that this is consistent with someone sustaining cuts or damage to the fingers prior to prints being taken, which would then affect the print image.
"Had these been powder marks or smudges as claimed, we would expect to see a complete fingerprint image.''
Mr Burgess said the theory put forward by 3rd Degree was an interesting idea when taken in isolation, but was no more than a theory when taken out of context of all the other evidence which has been presented to several courts.
"Marks on a photograph can always be open to several interpretations by experts, and the significance or relevance of these marks have not been tested in court,'' he said.
"Examination of the original photograph does not give any definitive indication of what the marks could be. There are other possibilities, including that they are minor cuts.''
Mr Bain was working on the roof and spouting of his Every Street home in the days leading up to the killings, Mr Burgess said.
"Any Kiwi handyman knows the sort of damage this can do to the hands. Post mortem examination of Robin Bain's hands shows a number of minor abrasions and marks you would expect to find with someone familiar with manual work.''
Evidence put forward in court was that the only identifiable fingerprints found on the gun belonged to David and Stephen Bain, Mr Burgess said.
"Police will continue to look at this issue to gain a better understanding of what this photograph may show.
"However, I am mindful that this theory has been put forward through a programme whose makers chose not to seek comment from police prior to broadcast, and who also refused to provide details about their story when approached by police on Tuesday,'' Mr Burgess said.
"Had they done so then we would have pointed out that fingerprints had been presented in evidence and have always been available through the court to help them decide if their story stacked up.''
No immediate pardon - PM
The new evidence didn't automatically mean David Bain will be awarded compensation or an immediate pardon, Prime Minister John Key said today.
Mr Key said he didn't watch TV's 3rdDegree programme last night which claimed parallel marks on the thumb of Robin Bain are consistent with those made when loading a rifle's magazine which has recently been fired.
David Bain's supporters say it further clears his name for the 1995 killings and should pave the way for an immediate pardon.
Prime Minister Robert Muldoon issued a pardon in 1979 for Arthur Allan Thomas, twice convicted for the murders of Waikato farming couple Jeanette and Harvey Crewe, and jailed for nine years.
But Mr Key wasn't rushing down the same track with David Bain.
"Firstly, you can't join the dots from one case to another, they are completely independent and have no correlation with one another," he said.
"Secondly, to issue a royal pardon, you have to meet a certain test, and it's the same issue of whether compensation gets paid.
"The test for whether someone is found not guilty is beyond reasonable doubt - that is a very different threshold to even the threshold that would need to be reached before the Crown could pay compensation, and that threshold is essentially one of proof has to be shown that someone else actually committed the crime. Now, again, the Crown would have to take advice on all those issues."
Mr Key said he couldn't comment much further on the new revelations, given that Bain's claim of compensation, which is before the courts, has been "put on hold at the request of the David Bain negotiating team".
And asked if a new report should be ordered given the new revelations, Mr Key said he'd have to take advice on that and wait for the court proceedings to come to a conclusion.
The latest revelations in the long-running Bain saga suggest it would be worth investigating setting up an agency - similar to the UK criminal cases review commission - to review difficult cases here, Labour's justice spokesman Andrew Little said.
"The on-going controversy over the case - with two juries reaching two different verdicts, a so-called independent inquiry into compensation being overturned by the minister of justice and now apparently 'new' evidence that has, in fact, been around all the time - calls into question the effectiveness of our judicial system," he said.
A criminal cases review commission could be made up of investigators drawn from the judiciary, the police, scientists and other experts, he said.
Mr Little said they could conduct a thorough re-examination and extended investigation if needed to deal with all alternative possibilities, not just those that fit neatly into the court rules of evidence.
"If a miscarriage of justice is found then the same independent process could be used to assess compensation. The process we use now is clearly open to political interference.
Mr Key was unsure if Mr Little's plans had any merit.
"I haven't had any advice on that," he said.
"We may at one point want to do that, but again wouldn't want to jump to conclusions."