Colm Murphy and Seamus Daly are contesting civil court decision that found them liable for 1998 atrocity
Two men sued by the relatives of those killed in the Omagh bomb massacre, who claimed the pair were leading figures in the Real IRA, were due to begin their appeal against a civil trial ruling in Belfast on Monday.
The retrial at Belfast high court of Colm Murphy and Seamus Daly is taking place after they successfully appealed against a civil court decision that found them liable for the 1998 bombing in which 29 people were killed including a woman pregnant with twin girls.
The case was due to start last November but was delayed due to the illness of one of the lawyers involved. It is expected to last about six weeks.
The Real IRA founder Michael McKevitt, who was a brother-in-law of IRA hunger striker Bobby Sands, and his dissident republican colleague Liam Campbell failed in their 2011 bid to have the 2009 civil court judgment against them overturned.
In that case, McKevitt, Campbell and Murphy and Daly were found liable for the bombing and were ordered to pay £1.6m in compensation to the families. No one has been criminally convicted for the Omagh bombing. McKevitt and Campbell are seeking to go to the European court of human rights. Campbell is facing extradition charges to Lithuania where he is wanted for questioning over a Real IRA arms smuggling operation.