One of the men held liable on a retrial for the Omagh bomb atrocity was denied a fair hearing due to the judge's knowledge of previous evidence, the Court of Appeal heard today.
Seamus Daly was linked by a call made on one of the mobile phones allegedly used by the Real IRA team who carried out the attack.
But his lawyers argued that a witness who took the call less than half an hour after the blast said it came from a man named Seamus Healy.
They claimed it was wrong to find that Denis O'Connor was actually referring to Daly.
Mary Higgins QC contended: "What happened in this case is that the judge was coloured.
"It's the most likely explanation for why he interpreted Mr O'Connor's evidence in the way he did."
Daly, from Culaville, County Monaghan, and his former boss Colm Murphy, a Dundalk-based builder and publican, are appealing a second High Court verdict which identified compelling and overwhelming evidence of their connection to the massacre.
Twenty nine people, including the mother of unborn twins, were killed in the August 1998 attack. Hundreds more were badly injured.
No-one has ever been convicted of carrying out the bombing in a criminal court.
But relatives of some victims brought a landmark civil action against those they suspected of being connected.
Murphy and Daly 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.
At the retrial the judge decided on the balance of probabilities that Daly called Mr O'Connor on the day of the bombing on one of the phones allegedly supplied by Murphy.
But Ms Higgins today contended that it was wrong to infer it was her client, rather than a Seamus Healy, who made the call.
She claimed: "The close familiarity of the evidence given in previous cases... did lead to unfairness in relation to this particular appellant because of the way it caused the judge to interpret the evidence of Denis O'Connor."
The barrister further contended there were examples of "tunnel vision" in the case.
"Certain facts which supported this appellant's case were discounted and certain facts which did not support the plaintiffs' case and from which adverse inferences could have been drawn were discounted as well."
The appeal continues.