The Supreme Court has begun hearing an appeal against a High Court ruling last month that the families of some of the victims of the 1998 Omagh bombing are entitled to some, but not all, of the documentation they had been seeking for the trials of five men.
The families had been seeking the books of evidence and the transcripts of criminal trials involving each of the five men, to use them in proceedings for damages against the men.
They argued the documents were relevant to the action, which is due to take place before the High Court in Belfast next week.
The men opposed the application on the grounds that there was an impediment in law that prevented them from handing over the documentation and they could be in contempt of court by doing so.
The High Court ruled last month that books of evidence could be disclosed but the court found there was an impediment under Irish law preventing the defendants from handing over the transcripts of their trials at the Special Criminal Court.
Both the families and the five men have appealed the judgment to the Supreme Court.
The five men against whom discovery is being sought include Michael McKevitt, Beech Park, Blackrock, Co Louth, who is serving a 20 year sentence for directing terrorist activities for the Real IRA.
The Supreme Court has reserved judgment on his appeal against his conviction.
The five also include Seamus Daly, from Culloville, Castleblayney, Co Monaghan, who was sentenced to three years after being found guilty of membership of an illegal organisation and Liam Campbell, from Upper Faughart, Dundalk, who was jailed for membership of an illegal organisation.
The fourth man is Seamus McKenna, formerly of Silverbridge, Co Armagh,but with an address at Marian Park, Dundalk, who was sentenced to six years' imprisonment for unlawful possession of explosives. They have all completed their sentences.
The families are also seeking certain materials relating to criminal proceedings taken against Co Armagh native Colm Murphy with an address at Jordan's Corner, Ravensdale, Co Louth, who is facing a re-trial on a conspiracy charge.
Mr Murphy has denied conspiring in Dundalk with another person not before the court to cause an explosion in the State or elsewhere between 13 and 16 August, 1998.
