Ian Bailey today won a two-year legal battle against his extradition to France over the killing of Sophie Toscan du Plantier in west Cork 15 years ago.

The Supreme Court in Dublin ruled Ian Bailey cannot be sent for questioning about the killing.

Ms Toscan du Plantier, 39, was found beaten to death outside her holiday home in Schull, west Cork, two days before Christmas 1996.

Mr Bailey, a one-time suspect in the investigation, has always protested his innocence.

The five judges in Ireland’s highest court upheld his appeal and ruled that under Irish law the 54-year-old former journalist could only be extradited to face prosecution, and not for questioning.

An investigating magistrate, Patrick Gachon, was appointed in Paris to conduct an inquiry into Ms Toscan du Plantier’s death after the DPP announced nobody would be charged in Ireland following a Garda investigation.

Under French law, authorities can investigate the suspicious death of a citizen abroad but they cannot compel witnesses to go to Paris for questioning.

Mr Bailey was arrested and questioned twice by gardaí after Ms Toscan du Plantier's killing but never charged.

He cupped his ear to hear better as the judges delivered their verdicts one by one, and hugged his partner, Jules Thomas, when the unanimous ruling was delivered.

The Chief Justice, Susan Denham, said the appeal from a High Court decision arose in unique circumstances and raised unprecedented questions of law.

“It is clear from the facts of the case on the documents before the court that, while a decision has been made in France equivalent to charging the appellant, that decision does not incorporate a decision to try him for the murder of Mme Toscan du Plantier,” she said.

Outside Dublin’s Four Courts, Mr Bailey, who is taking legal action against the State for wrongful arrest, said he and Ms Thomas have been through hell.

“This has obviously been a very trying time,” he said.

“I am obviously relieved that this particular part of the proceedings is over. There are many stages and matters still to be dealt with.”

Mr Bailey said the last few years have been very hard.

“You wouldn’t be able to believe the hell that we have been put went through by this awfulness,” he added.

The State will now have to pay his hefty legal bill for the High and Supreme Court hearings.

The dramatic twist in the long-running case came on the third day of Mr Bailey's appeal in January when a state barrister produced a translated arrest warrant from Mr Gachon which indicated that no decision has been made to charge the suspect.

His solicitor Frank Buttimer said why that matter was not addressed when first argued by Mr Bailey’s barristers in the High Court was a question for Justice Minister Alan Shatter.

“What has surprised me is the political silence in relation to the events that have been clearly laid out in the court and which are now in the public domain,” he added.

“I don’t think it’s for citizens or people in these circumstances to make calls (for an inquiry) I think it’ for people in authority to take stock of what has happened now and take a serious look at the various issues concerning this case.”

New material criticising the original Garda investigation also emerged last year.

Documents provided to Mr Bailey’s lawyers by the state last November included a 44-page review of the conduct of the murder investigation in 2001 and the reasons why the former director of public prosecutions (DPP) decided not to prosecute.

Mr Justice Adrian Hardiman said the material also alleged an unnamed senior garda or gardaí tried to get the former state solicitor for west Cork to put political pressure on the DPP to prosecute Mr Bailey.

“This attempt was resisted by the person who was asked to set it in motion,” the judge said.

Four of the judges also upheld Mr Bailey’s argument that – under Section 44 of the European Arrest Warrant Act 2003 – France has no right to exercise extra-territorial jurisdiction over Ireland as France would not be obliged to surrender a non-Irish citizen to Ireland in similar circumstances.

A lawyer representing the elderly parents of Ms Toscan du Plantier said they were disappointed and surprised by the ruling.

Alain Spilliaert warned the French investigation into her death would continue, adding there could be a trial in Mr Bailey’s absence based on the evidence of Irish witnesses by French investigators and a fresh extradition requested.

“This is not the end of the battle,” he added.

Mr Bailey is also expected to take legal steps to have the European Arrest Warrant for him lifted.