A builder accused of supplying mobile phones to the Omagh bombers should not have been held liable based on his failure to testify, the Court of Appeal has heard.
Lawyers for Colm Murphy argued that refusing to give evidence did not prove the case against him on the balance of probabilities.
Three senior judges were also told the extent of his alleged involvement has been reduced to a disputed link between his phone and the attack.
Murphy and another republican, Seamus Daly, are seeking to overturn a High Court verdict which identified compelling and overwhelming evidence of their connection to the atrocity.
Twenty-nine people, including the mother of unborn twins, were killed in the August 1998 attack. Hundreds were also badly injured.
Although no one has ever been convicted in a criminal court, relatives of some victims brought a landmark civil action against those they suspected of being connected.
Murphy, a Dundalk-based contractor and publican, and his former employee Daly, from Culaville, Co Monaghan, have already successfully appealed once against being held responsible, in an initial ruling in 2009.
Two other men, convicted Real IRA leader Michael McKevitt and fellow dissident republican Liam Campbell, failed to have the findings against them overturned.
During a retrial it was claimed that Murphy supplied mobile phones to the bomb team.
Daly was allegedly linked by a call made on one of the phones just after the explosion.
In March, a second High Court judge ruled both men were liable on the balance of probabilities.
He identified compelling circumstantial evidence that two mobiles linked to Murphy were used in the attack.
The same verdict was returned against Daly.
The ruling left both defendants liable for an award of damages previously set at £1.6m.
But as their second appeal hearing began in Belfast this week, defence lawyers disputed the strength of the case against them.
Dermot Fee QC, for Murphy, insisted: "There's no evidence these phones were in contact with anyone engaged in terrorist activity."
Murphy's reason for refusing to testify was previously given as being due to his lack of confidence in the judicial system.
Mr Fee stressed that much of the original case against his client – including the emails of FBI spy David Rupert – is no longer being relied upon.
The hearing continues.