The organisation led by convicted Real IRA leader Michael Mc Kevitt was responsible for "murder and mayhem on this island", his appeal heard today.
State counsel Mr George Birmingham SC said that Mc Kevitt's organisation was responsible "for the murder of men, women, children and unborn children and has sought to subvert the Constitution of this State".
Mr Birmingham, in legal submissions for the State on the third day of McKevitt's appeal against conviction for directing terrorism, said that the State was obliged by the Constitution and by international agreements to bring the particular individual who led that organisation to trial.
McKevitt (aged 54), of Beech Park, Blackrock, Co Louth was jailed for 20 years by the Special Criminal Court in August 2003 after he was convicted of directing the activities of a terrorist organisation between August 29, 1999 and October 23, 2000.
He was the first person to be convicted in the State for the offence which was introduced after the Real IRA bomb attack in Omagh in 1998 in which 29 people died.
Mc Kevitt also received a six years concurrent prison sentence for membership of an illegal organisation which the court said was the Real IRA. Mc Kevitt was in court for the appeal which was also attended by his wife Bernadette Sands McKevitt.
Mr Birmingham told the Court of Criminal Appeal today that FBI agent and supergrass David Rupert, who infiltrated the Real IRA and who was the chief prosecution witness in Mc Kevitt's trial, had performed tasks that he had agreed to do with "remarkable skill, resourcefulness and courage".
"His courage and resourcefulness has served all the people of this State," he added.
Mr Birmingham said that the decision to bring Mc Kevitt to trial was unique in that it involved three different states, with three different law enforcement agencies, each with a commitment to the rule of law.
He said the Director of Public Prosecutions had gone to elaborate lengths to ensure that McKevitt was given a fair trial.
"The disclosure that took place in this case was without precedent in the history of this State,'' he added. It involved impressing upon the FBI and British Security Service the necessity for full disclosure to the defence of all relevant material.
Mr Birmingham said that this even involved making officers of the British Security Service available for interview by lawyers retained by McKevitt.
Mc Kevitt's lawyers have appealed against conviction on the grounds that there was not full and proper disclosure of all material relating to David Rupert and that the Special Criminal Court erred in law by not adequately assessing Rupert's credibility as a prosecution witness despite his history of involvement in criminality.