Former "Real IRA" leader Michael McKevitt is to learn today if he has succeeded in his bid to overturn his conviction for directing terrorism.
McKevitt, (54) from Beech Park, Blackrock, Co Louth, was jailed for 20 years in 2003 under legislation introduced after the Omagh bomb in August 1998.
The Court of Criminal Appeal is set to deliver its judgment this afternoon.
McKevitt's legal team outlined 42 separate appeal grounds during a four-day hearing at the court last month. These focused on the credibility of David Rupert, the FBI and British secret service agent who was central to the prosecution case against McKevitt.
Mr Rupert was paid $1.25 million dollars (€1.1 million) to infiltrate the "Real IRA".
McKevitt is one of a number of people being sued in a civil action by some of the families of the 29 people killed in the bombing.
At the original trial in the Special Criminal Court in Dublin, he was also convicted of IRA membership and given a six-year sentence to run concurrently.