Four men will today begin a court appeal after they were successfully sued by families bereaved in the Omagh bombing.
An FBI agent whose evidence was crucial in the case against a dissident republican leader found liable for the Omagh bombing is a pathological liar, an appeal court heard today.
Testimony from American undercover operative David Rupert, who claimed to have infiltrated the Real IRA, was key in the successful civil action against Michael McKevitt.
McKevitt and three other republicans, Seamus Daly, Liam Campbell and Colm Murphy, were found responsible in the landmark civil case taken by bereaved relatives in 2009.
The four men began an appeal against the judgment in Belfast High Court today.
The bombing in the Co Tyrone town on August 15th, 1998 killed 29 people, including a woman pregnant with twins. More than 200 were injured in the car bomb explosion.
While Rupert did not give evidence at the civil trial in Belfast High Court. Testimony he had given against McKevitt at his 2003 criminal trial in Dublin for directing terrorism was submitted.
Opening the appeal case, his barrister Michael O'Higgins said objective evidence showed Rupert was a liar.
"Mr Rupert is a pathological liar and a confidence trickster, and a man who it was very strongly submitted (at civil case), a submission based on forensic investigation, engaged in serial perjury in the course of giving his evidence in the Dublin trial," he said.
Mr O'Higgins said the fact Rupert had not given evidence in the civil case denied McKevitt an opportunity to cross examine the witness.
In a separate move, relatives who were among those that lost loved ones in the attack are also appealing the £1.6 million in compensation recommended in June 2009 after their historic civil action.
No one has ever been successfully convicted of the Omagh bombing, with the only man jailed in connection with the attack, 57-year-old Co Louth builder Colm Murphy, cleared by a retrial in Dublin.
In December 2007, Sean Hoey (38) from Jonesborough, South Armagh, was cleared at Belfast Crown Court of murdering the 29 people. He was acquitted of 58 charges, including some not directly linked to the bombing.
The families' ground-breaking multimillion-pound civil action was described by them as an attempt to bring as much information into the public domain as possible.
It was the first time a civil action had been brought in a case of its kind. The legal bid cost an estimated £2 million.
The families were supported in their efforts to raise funds for the court case by former US president Bill Clinton, former Northern Ireland secretaries Peter Mandelson and Sir Patrick Mayhew, as well as musician Bob Geldof and boxing champion Barry McGuigan.
The 12 relatives who launched the landmark civil action said they had done so because of the failure of the authorities to secure a successful criminal conviction over the attack and they sued the men who they accused.
PA