Michael McKevitt, who is serving a 20-year sentence after becoming the first person in the State to be convicted of directing terrorist activities, has begun a Supreme Court appeal against his conviction.
McKevitt (54) claims he did not get a fair trial because his legal team had not been supplied with all information in relation to a key witness, FBI agent David Rupert.
That information was material to the credibility of Mr Rupert and, if provided, would have shown the secret services' "attempt to mask" Mr Rupert's alleged criminality, Hugh Hartnett SC, for McKevitt, said.
Mr Hartnett was opening the appeal by McKevitt, of Beech Park, Blackrock, Co Louth, who was jailed by the non-jury Special Criminal Court in August 2003 for organising terrorist activities for the Real IRA.
The evidence of Mr Rupert, who was described by the judges at the Special Criminal Court as "very truthful", was a key part of the prosecution case.
McKevitt appealed to the Court of Criminal Appeal, which upheld the conviction in 2005. However, it later certified that a point of law arose in the case requiring determination by the Supreme Court, a decision which effectively clears the way for a full appeal to the Supreme Court.
The five-judge Supreme Court, comprising the Chief Justice, Mr Justice John Murray; Ms Justice Susan Denham; Mr Justice Adrian Hardiman; Mr Justice Hugh Geoghegan and Mr Justice Nial Fennelly, began hearing that appeal amid tight security yesterday. McKevitt, who boycotted his original trial for some time, was in court.
He was the first person to be convicted in the State for the offence of directing terrorism, which was introduced after the Real IRA bomb attack in Omagh in 1998 in which 29 people died.
When he was convicted by the Special Criminal Court in 2003, the judges stressed the offences did not relate to the Omagh bombing but related to a later period.
In turning down his appeal in 2005, the Court of Criminal Appeal rejected McKevitt's argument that the original conviction was unsafe because of the unreliability of Mr Rupert.
McKevitt's appeal to the Supreme Court centres on issues concerning the reliability of Mr Rupert, who infiltrated the Real IRA and attended Real IRA army council meetings where he alleged McKevitt was present.
The Court of Criminal Appeal was told Mr Rupert had been paid $1.4 million by the FBI and £400,000 by the British security service.
In submissions yesterday, Mr Hartnett said the trial before the Special Criminal Court failed to have an appropriate system of disclosure of documents which were crucial to his client's case.
The disclosure would have included information about Mr Rupert having been allegedly investigated for fraud in 1974 and 1994, which was relevant to his motivation for acting as an FBI informer.
Mr Rupert was described in a report by an American state trooper as being involved, using a trucking firm set up by him, in theft and people/arms smuggling between the US and Canada, Mr Hartnett said.
His failure to be prosecuted for these activities and his later being signed up by the FBI were relevant to the integrity of his motivation for giving evidence in the case against McKevitt, Mr Hartnett said.
No schedule of documentation was ever presented to the defence and McKevitt's lawyers got material relating to Mr Rupert's alleged criminality "by chance or mistake".