The former president of New Zealand Criminal Bar Association says the leaking of the findings of a confidential report on David Bain's compensation bid could force yet another investigation.

Gary Gotlieb said he was shocked that such a sensitive piece of information had been leaked.

"The procedure is quite clear. You follow a process where this is confidential and until the matter is all signed off and agreed between parties it's just a complete no-no that you make anything public."

READ MORE: Mike Hosking - Why David Bain deserves compensation

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The report, written by a senior judge, found that Bain did not meet the threshold of "innocent beyond reasonable doubt", dealing a blow to Bain's compensation claim for wrongful imprisonment.

The report has just been delivered and the Government has not yet begun any consideration of the latest development in the Bain case, which has divided the country for years.

Ian Callinan, QC, a retired judge from Australia, was asked to advise whether he is satisfied that Mr Bain has proven he is innocent of murder on the "balance of probabilities" and, if so, whether he is also satisfied Mr Bain has proven he is innocent "beyond reasonable doubt".

Mr Gotlieb said there was a possibility the leaking of the report could prejudice Bain's bid for compensation and predicted there would be people on the warpath hunting for whoever was responsible.

He was also surprised the Bain case appeared to be subject to an higher threshold of innocence beyond reasonable doubt when Cabinet rules for compensation referred to innocence on the balance of probability.

Ms Adams today confirmed she has received the report but she was not prepared to give any details about its contents.

"I can confirm that I have received Mr Callinan's report. In accordance with the agreed process, parties now have an opportunity to provide any further information they wish me to consider in respect of the report," she said.

"I will not begin consideration of Mr Callinan's report and the advice I will take to Cabinet, until I have that information."

She said there would be no further details until a decision had been made by Cabinet on the Bain compensation.

She did not provide a timeframe. "To protect the integrity of the process, it has been agreed with the applicant that there would be no comment on the status or position of the claim until Cabinet has made its decision and accordingly I won't be providing further detail until that time."

Mr Bain was convicted of murdering his parents and three siblings in June 1994 by shooting them with a .22 rifle. He served almost 13 years of his minimum 16-year life sentence. The Privy Council quashed his convictions in 2007 and ordered a retrial. He was acquitted after a three-month retrial in Christchurch in 2009.

The Herald understands that the judge did not find that Mr Bain is innocent beyond reasonable doubt - the benchmark for "extraordinary circumstances" required for compensation under previous guidelines.

There are expected to be different views within the Cabinet as to whether to pay nothing at all, or to explore some avenue that might end further litigation, such as assisting with Mr Bain's legal fees.

Ms Adams will make the eventual recommendations to Cabinet after sounding out her colleagues.

It's the latest twist in a compensation claim which has dragged on since 2010. An earlier inquiry - by retired Canadian judge Ian Binnie - recommended compensation. The Government did not accept the finding after a peer review, by a retired New Zealand judge, found he had parts of the law wrong.

Mr Bain challenged the process in court but the case was halted in a confidential settlement with the Crown last year, paving the way for a fresh review of Mr Bain's application for compensation by Mr Callinan.

Ian Binnie talks to Newstalk ZB's Mike Hosking (app users tap here)

If Mr Bain had been successful in his application, he could have received up to $2 million on estimates from other successful compensation claims.

In appointing Ian Callinan to hold a fresh inquiry, Adams said his role was to provide advice on questions relevant to the Cabinet's decision on compensation.

At first, Mr Callinan was asked to advise whether he is satisfied that Mr Bain has proven that he is innocent of murder on the "balance of probabilities" and, if so, whether he is also satisfied Mr Bain has proven he is innocent "beyond reasonable doubt". Mr Callinan was being asked the latter question at this stage because the Cabinet had previously treated innocence beyond reasonable doubt as an example of "extraordinary circumstances", Ms Adams said.

The "balance of probabilities" is the burden of proof required for a civil trial, where one party's case needs only to be more probable than the other. In a criminal trial, the burden of proof for the Crown is "beyond reasonable doubt", where a judge will often tell the jury they must be sure of guilt to convict.

An estimated $1 million has been spent on hiring the three former judges to consider the compensation application. It has also involved three Justice Ministers: Simon Power, Judith Collins and Ms Adams.

Ms Adams refused to comment on the Callinan report, even to confirm if a draft version was complete.

"There are a number of steps in the claim process, including: completing a draft, finalising the report, seeking further comment from the parties, and formulating advice to Cabinet. This process is well under way but is not yet complete," she said. "To protect the integrity of the process, it has been agreed with the applicant that there would be no comment on the status or position of the claim until Cabinet has made its decision ... "

On the way into the debating chamber today, Justice Minister Amy Adams said she would not make any comment on what the report said.

"What I am concerned about is that there is all sorts of speculation, some of which is quite inaccurate, and while it is a matter of high public interest, it really is important that the commentary and analysis waits until people can see and read what Mr Callinan has actually said."

She said the leaking of its contents was "terribly disappointing", but she did not know where it had come from.

"Some of what I have seen is inaccurate, which raises questions about what they think they have or don't have."

Last night, Mr Bain, who is now married with a young son, said: "I've got no comment to anything at the moment".

But long-time supporter Joe Karam said the fight for compensation was far from over.

"There is a lot of water to go under the bridge, as the Minister's statement indicates, before the compensation claim is resolved."

Mr Binnie told the Herald the Government should take its lead from the court of public opinion and compensate Mr Bain for wrongful imprisonment.

"I think they should do the right thing. I concluded that the evidence was sufficient to establish on the balance of probabilities that he was innocent. Another former judge has taken a different view but the Government is ultimately responsible to the New Zealand public and the public has spoken very clearly in favour of David Bain so I don't think the Government is going to be able to hide behind the report of Mr Callinan or anybody else."

He said New Zealanders had made up their minds of the guilt or innocence of David Bain.

"Everybody seems to have a strong and immovable opinion and, from what I've read from time to time, the majority seem to have concluded that he's innocent. The last figures I saw were somewhere between 65 and 70 per cent thought he should be compensated so really whether he's able to prove his innocence to Mr Callinan's satisfaction 20 years after the event is a matter of argument."

He said there were "real problems" with the Government's position especially given the destruction of the Bain house containing essential evidence three weeks after the killings.

"The reality is when somebody says David Bain can't prove this or that, we'll he'd be in a better position if they hadn't burned up the evidence.

"I don't think these reports are going to resolve the problem for the Government. I think what counts is the court of public opinion and there seems to be a strong majority in David Bain's favour and I think ultimately that will drive the result."

He said the Privy Council spoke very clearly the conviction was wrongful and the prosecution proof found wanting.

"It strikes me that the message from the Privy Council was the prosecution's proof was clearly inadequate. Again that's the view of five judges on a New Zealand issue. But it is strange, apart from Mr Callinan, that all of the foreign judges who have looked at this case have rejected the prosecution's position."

The Callinan report took nearly 12 months to complete, twice as long as the expected six months.

It comes more than three years after the original inquiry into compensation by Mr Binnie, who concluded Mr Bain was innocent "on the balance of probabilities" - a lower evidential threshold than "beyond reasonable doubt" - and should be granted compensation.

But Ms Collins ordered a peer review by Robert Fisher, QC, a former High Court judge, which found the former Canadian judge made several errors of law. She rejected the recommendations of Mr Binnie, so Mr Bain launched legal action to challenge her decision, in a judicial review proceeding alleging Ms Collins acted in bad faith, abused her power, and acted in a biased, unreasonable and predetermined manner.

Following a confidential agreement between Mr Bain's legal team and the Minister of Justice, the judicial review case was halted and Ms Adams, now the Justice Minister, announced a fresh inquiry. The Binnie and Fisher reports cost $600,000, while the Callinan report is expected to cost another $400,000.

The announcement of the Callinan inquiry prompted Mr Binnie to criticise the Government.

"It seems the Government is looking for somebody to give them the opinion they want, which is that David Bain should be denied compensation," the former Supreme Court member said. "The problem now is that the Government has made it loud and clear what answer it wants and anybody taking on the assignment would see what happened to me for giving an answer that the Government didn't want."

Opposition justice spokeswoman Jacinda Ardern hoped this marked the end of a judicial process that was proving to be a long, drawn-out affair.

The ongoing litigation surrounding the compensation bid had been a "far from perfect" and costly process, she said.

It needed to be scrutinised by politicians to ensure any future compensation cases were handled in a less costly, tighter timeframe.

"We need to make the process robust. All parts need to have a fair hearing so the public can see the right outcome for everyone involved and people can have faith in the eventual decision," she said.

She said the Bain case held huge public interest with most New Zealanders holding an opinion as to his guilt or innocence.

While it was important to get the right decision it was time for the legal action to stop.

"Whatever the outcome the Minister of Justice does need to see an end to litigation in this case," said Ms Ardern.

The Government will be weighing up the mood of the public ahead of reaching a decision on giving compensation to David Bain.

Otago University Law Professor Mark Henaghan said any matter of compensation was a political process where governments chose to compensate people if they thought it was politically appropriate.

He said in any bid for compensation cabinet would seek independent legal advice to assess the innocence of the person.

This could be set at different standards. In some cases innocence needed to be proved on the balance of probabilities and some beyond reasonable doubt.

Mr Henaghan said submissions would be sought from all parties connected to the case.

Cabinet would then discuss the next step taking into account the independent advice and submissions.

At all times cabinet would weigh up the political implications and question whether it could justify giving away public money.

"Ultimately it's a political decision and public money so governments have to justify that there is sufficient evidence and justification to say we got it wrong and pay appropriate compensation," said Mr Henaghan.

There was no time frame for this to take place.

"There's no requirement for Governments to compensate - it's not a legal requirement - but Governments do it as a matter of goodwill.

"If there is clear evidence that somebody's obviously innocent and spent a lot of time in prison and it was wrong then most people would say it's unfair not to compensate them."

However, if the evidence was not clear then there would be less political will to pursue compensation.

Mr Henaghan said if the government refused compensation there was an outside possibility the defence could seek a court review.