An agent of the Federal Bureau of Investigation, who is due to give evidence against Mr Michael McKevitt, alleged to be the leader of the "Real IRA", "represents a very serious threat to a very dangerous organisation", the Special Criminal Court was told yesterday.
Mr George Birmingham SC, prosecuting, said the State had concerns about Mr David Rupert and was anxious to get an early trial for Mr McKevitt.
"He is somebody who represents a very serious threat to a very dangerous organisation. That is something we are very conscious of," Mr Birmingham said, adding:
"We are conscious of the fact that Mr Rupert is somebody who set out to infiltrate at the highest level the leadership of the 'Real IRA'. That is an act of bravery and courage."
Mr McKevitt (51), Beech Park, Blackrock, Dundalk, Co Louth, is charged that between August 29th, 1999, and March 28th, 2001, within the State, he was a member of the IRA, otherwise Óglaigh na hÉireann. He is also charged with directing the activities of the same organisation.
It is the first prosecution for directing terrorism under legislation brought in after the 1998 Omagh bombing, and anyone convicted of the offence faces a maximum sentence of life imprisonment.
Mr Rupert, who worked for the FBI and British intelligence, is the chief prosecution witness in the forthcoming trial of Mr McKevitt.
Last December the court provisionally fixed June 4th as the date for Mr McKevitt's trial, which is expected to last at least four weeks.
However, the defence has sought disclosure of material from the prosecution relating to Mr Rupert and has said it is unlikely the trial will go ahead on that date.
Mr Birmingham told the court yesterday that contact was made with the FBI concerning two criminal investigations of which Mr Rupert was the subject, and this material had been furnished to the defence.
He said one channel remained to be explored with the British authorities, and the prosecution wanted to be satisfied that the material was relevant before furnishing it to the defence.
Mr Justice Barr said it might be necessary for the court to look at that material to see if it was relevant.
Mr Birmingham said the State accepted that this was a case where there should be extensive disclosure, and extensive disclosure had taken place.
The court was told earlier that the defence had already been furnished by the prosecution with more than 2,000 e-mails relating to the case.
The court was also told at an earlier hearing that Mr Rupert was the main prosecution witness. He worked for the FBI and British intelligence and was observed by gardaí meeting Mr McKevitt on a number of occasions.
The court also heard that he successfully infiltrated the "Real IRA" leadership and attended its Army Council meetings.
The court has also been told that Mr McKevitt met Mr Rupert over a two-year period and asked him to acquire equipment for the dissident republicans.
Mr McKevitt was remanded in continuing custody until May 16th when the case will be mentioned again.