Prime Minister John Key says he does not expect an apology will be made to the "Urewera 18", after the Crown yesterday revealed 13 of the 17 defendants in Operation Eight would be discharged.

The move came after a Supreme Court decision ruled crucial police evidence was inadmissable at trial.

Speaking to media this morning, Mr Key defended the actions of the police.

"I'm not in a position to comment, I haven't had any advice on that, but I would be surprised if that is the case," Mr Key said.

"It is my view that the police acted because they believe there was a risk," he said. "I believe the police acted with the best intentions because they believed there was a risk."

Meanwhile the Tuhoe leader at the centre of alleged military-style training camps has questioned why four of the group will stand trial when firearms charges against the rest were dropped.

Tame Iti said the decision to press ahead with firearms and organised crime charges against him and three others was madness when the prosecution against the other accused was abandoned.

But Iti still faces 10 charges of unlawful possession of firearms and restricted weapons, including Molotov cocktails and military-style rifles such as the Saiga MK03.

The longtime Maori activist re-affirmed he would defend the "baseless" charges laid against him after the police "terror raids" in October 2007.

"I'll defend them for as long as it takes," he told the Herald from his home in Ruatoki, Bay of Plenty.

Iti said he failed to understand why charges were dropped against some, but not all, of the defendants.

The ruling does not affect the trial of Iti, Emily Bailey, Te Rangikaiwhiria Kemara and Urs Signer on firearms and organised crime charges.

"It's a really dumb process. What's the difference between them and us?"

Mr Iti likened the four-year court process as a game of chess that he was forced to play.

He was to meet his defence team to discuss the implications of the Supreme Court ruling.

Mr Iti said the raids and the case had deepened Tuhoe's distrust of the state, but the iwi was still trying to move forward.

"Tuhoe has never trusted the state. For well over 100 years, Tuhoe has been attacked by the state.

"We've been marginalised and undermined, but for the last 10 to 15 years, before the terror raids, we've been moving on through the Waitangi Tribunal process."

The Supreme Court has ruled certain evidence inadmissible at the trial which was to begin next February and last for three months.

The decision overruled previous judgments from the High Court and Court of Appeal over whether the Crown could use evidence gathered in the covert police operation before the arrests in October 2007.

One of the original "Urewera 18" was Tuhoe Francis Lambert, who died this year. He would have faced trial with Iti in February.

Omar Hamed, Valerie Morse and Jamie Lockett are among the 13 who will no longer stand trial after the Supreme Court decision.

Mr Hamed said he spent the last four years waiting for the trial to begin.

"The stress of it ... the stress on your family, friends, relationships and on your work means you cannot plan."

Ms Morse described the case as a "disaster from start to finish".

"They arrested us and put us in prison while they tried to charge us with terrorism.

"That failed. Now after four years, millions and millions of dollars, and systematic denial of rights to accused, the case has totally failed."

The reasons for the Supreme Court judgment remain under suppression orders.

As a result of crucial evidence being ruled inadmissable, the Crown no longer believes there is sufficient evidence to justify the Arms Act charges against 13 of the 17 accused.

The Auckland Crown Solicitor, Simon Moore, SC, said the Supreme Court decision meant separate trials would have been needed for those charged under the Arms Act and the four accused of the organised crime offences, resulting in further delays.

"The effect of the delay would be that those accused facing Arms Act charges alone would not be tried for a period of four and a half years from the date of their arrest," said Mr Moore.

"Further, they were remanded in custody for a period of time following their arrest, and they have been on restrictive bail conditions through much of the time since their release."

Taking these matters into account, Mr Moore said the Crown decision was that continuing proceedings would not be in the public interest.

The early-morning raids in October 2007 involved more than 300 officers in property searches in Auckland, Waikato, Bay of Plenty, Wellington and Christchurch using warrants alleging crimes under the Terrorism Suppression Act.

The Solicitor-General ruled out charges under the Terrorism Suppression Act - saying the law was "almost impossible to apply in a coherent manner" - but endorsed the firearms charges being laid.

- Additional reporting Edward Gay of APNZ

Emily Felicity Bailey, Tame Wairere Iti, Te Rangikaiwhiria Kemara, Urs Peter Signer.

* Jointly charged with participation in an organised crime group between November 2006 and October 2007.

* Jointly charged with unlawful possession of firearms and restricted weapons including shotguns, Molotov cocktails and military-style rifles.