Liam Campbell appeal heard in High Court in Belfast
The decision to block a dissident republican's extradition to Lithuania to face weapons smuggling charges was based on out of date information, the Court of Appeal has been told.
In January, a court refused to order Liam Campbell's transfer.
The judge said Campbell was likely to be held in inhuman and degrading conditions if extradited.
Campbell, 49, from Dundalk, was previously held liable for the Omagh bombing.
Judges heard on Wednesday that a critical examination of prison regimes in the Baltic state central to Mr Campbell's transfer being refused was carried out more than two-and-a-half years ago.
Attempts to have the 49-year-old extradited were denied last month on grounds that he was likely to be held in inhuman and degrading conditions.
Mr Campbell, of Upper Faughart, Dundalk, is wanted in Lithuania over allegations he was part of an operation to acquire guns, ammunition and explosives from there and ship them into Ireland for dissident republicans.
His lawyers resisted extradition proceedings by arguing that it would breach his human rights.
They brought in a special adviser to the British Home Office and the Council of Europe's Committee for the Prevention of Torture as part of their case.
Prof Rod Morgan visited Lukiskes Jail in Vilnius and delivered a critical assessment of prison regimes in Lithuania.
A judge refused to order the extradition after studying details of severely overcrowded and unsanitary conditions at Lukiskes.
He ruled that Mr Campbell would be at real risk of inhuman and degrading treatment by reason of the jail conditions.
Appealing that decision on Wednesday, Gerald Simpson QC, for the Lithuanian authorities, pointed out that Prof Morgan's visit was in May 2010.
"There is no evidence of what the position is today," he argued.
"The court is making a decision today on material that is two-and-a-half years out of date."
Lord Justice Girvan, sitting with Lord Chief Justice Morgan and Lord Justice Coghlin, pointed out that a series of reports have been prepared over the last decade.
"There is certainly not a picture of radical change to the underlying problems of overcrowding, in fact the trend seems to be getting worse," he said.
Mr Simpson replied that although inferences can be drawn, the information was not current.
"It's inappropriate to consider the evidence of 2010 as being current," he added.
However, Barry Macdonald QC, for Mr Campbell, contended that the issue was never raised during the extradition proceedings.
He said: "Even on the day of the last hearing, when final submissions were made about Article 3 (freedom from torture and inhuman treatment) issues, it was not suggested that the evidence was stale."
Following arguments judgment was reserved.
Mr Campbell was returned to custody where he is expected to remain until the verdict.
He has been in prison since he was arrested after crossing the border into south Armagh in May 2009.
A month later he was found liable, along with convicted Real IRA leader Michael McKevitt, for the Omagh bombing.
That ruling followed a landmark civil action brought by relatives of some of the 29 people killed in the August 1998 atrocity.
According to the judge at the time there was cogent evidence that Mr Campbell was a member of the Real IRA's Army Council.
Two other men originally held responsible, Dundalk-based builder and publican Colm Murphy and Seamus Daly, from Cullaville, County Monaghan, are currently facing a civil retrial after the findings against them were overturned on appeal.