Mystery remains over how former National Party leader Don Brash's emails entered into the public domain after police say they have given up the chase.
Wellington police district crime services manager Detective Inspector Harry Quinn said today the investigation into the theft had ended without identifying who was responsible.
"How the thefts occurred still largely remains a mystery," Mr Quinn said.
"We have eliminated the suggestion that an external 'computer hacker' had breached the computer security within Parliament, but there remains many other potential ways in which the crimes could have occurred."
Mr Quinn would not say how he reached that conclusion.
"There are a wide number of ways in which the thefts could have occurred and there is a lot of speculation about it.
"There is simply no evidence at all that the thefts were perpetrated by someone involved in the administration of the computer systems and there is evidence that the emails were not stolen in an electronic form."
Mr Quinn said inquiries also appeared to indicate the theft was not done by "a group of conspirators", but he would not elaborate.
The investigation established that emails created between October 2003 and November 2005 had been stolen from Dr Brash, but found no evidence of thefts since November 2005.
In late 2006, extracts from 475 separate Brash emails were used by Nicky Hager as the foundation for his book The Hollow Men.
Mr Hager would not tell police the source of the emails.
Other than two tabled during parliamentary debate, police did not locate any of the original stolen emails.
Mr Quinn would not speculate on how he thought the emails had been taken from Dr Brash.
"There are strong indications that the emails were in printed form at the time of the theft, but with the thefts perhaps happening at any time over the two-year period it is very likely that they were stolen during several incidents," he said.
Police interviewed parliamentary computer staff, parliamentary security staff, cleaners, Dr Brash's staff, politicians, journalists and friends of Dr Brash.
"Many of them had their own theories on who was responsible and why the thefts had occurred," said Mr Quinn.
"But in the end, no firm evidence pointing to a potential perpetrator was uncovered. The file is closed until someone comes forward with some compelling evidence."
Dr Brash said he was not happy with the outcome or the investigation itself.
"I am disappointed how long it took them to interview the obvious suspects ... They were very slow, there were people who referred to the emails in the House and they took too long to talk to them."
Dr Brash said he had no idea about who had taken his emails and none of the multitude of theories he had heard were entirely convincing.
He said the lack of answers continued to raise concerns for politicians about their security.
"It is worrying, not just for me, of course because I do not work there any more, but for everyone in Parliament."
New Zealand First Leader Winston Peters, who once tabled some of the emails and boasted to have a "telephone book" of them, said Dr Brash knew who did it.
"The leak was inside his office. I know that and so does Don Brash. Going to the police and laying a complaint was an absolute fraud," Mr Peters said.
Mr Peters refused to answer questions on whether he knew who it was.
After questions were raised over the emails, Mr Peters said that his copies had been destroyed by his staff without consulting him.
Prime Minister Helen Clark said the affair was mystifying.
"It's a very mysterious business this theft of the emails... and the fact that the police have not been able to draw any conclusions in the inquiry is disturbing."
Mr Hager has always maintained the emails were leaked to him by National Party sources and said those who claimed they were gained by theft should apologise to him.
National Party leader John Key said he still believed the party was the victim of a malicious hacker and he did not believe Mr Hager.
Police had taken too long to do their job.
"It's taken an awfully long time. I'm surprised they haven't been able to resolve the issue and there's very little to do about it other than say we're a bit frustrated."
