The judge hearing a multimillion-pound compensation claim by relatives of the Omagh bomb victims wants to take evidence in the Republic from 24 gardaí.
In a ruling in the Belfast High Court yesterday, Mr Justice Declan Morgan ordered that a formal request be made to the judicial authorities in Dublin for their help in securing the testimonies sought.
He said this was an exceptional course of action but was justified on the basis of the substantial body of evidence involved.
The Omagh families' £14 million (€18.8 million) civil action has been taken against Michael McKevitt, currently challenging a 20-year sentence for directing terrorism, and four others, Séamus Daly, Séamus McKenna, Liam Campbell and Colm Murphy.
They claim the gardaí could give details on the Real IRA and its leadership, and corroborate the evidence of David Rupert, the FBI spy who helped convict McKevitt.
Details of interviews and alleged admissions involving some of the defendants could also be backed by the gardaí, the families believe.
Mr Justice Morgan plans to cross the Border to head up a special commission where the Garda officers could give details on the alleged involvement within the Real IRA of the five men being sued.
The Government has said it will allow gardaí to tell what they know about the planning and implementation of the August 1998 bomb atrocity, which killed 29 people. But it has said this assistance depends on hearings being held in the Republic.
Mr Justice Morgan yesterday referred to uncertainty over the level of co-operation available from the Irish authorities in providing witnesses.
But he also said public interest immunity issues could prevent Garda officers travelling North to testify at the trial, which is due to begin on April 7th.
The judge said: "I am satisfied, therefore, that it is necessary in the interests of justice to make the order sought in respect of the 24 identified witnesses.
"I direct that a letter of request should be issued to the judicial authorities of the Republic of Ireland to facilitate the taking of that evidence."
The judge, who decided 24 Garda officers were relevant to the case, described it as an exceptional course for a judge to take testimonies on commission in another jurisdiction.
He justified it on the basis of the substantial body of possibly controversial evidence involved, saying it may be necessary to decide on the credibility of some witnesses. "Even though I would not be sitting as a judge I would be entitled to take into account the demeanour of the witnesses when answering questions.
"The second factor relates to the public interest immunity issues . . . It may become necessary as commissioner to give some assistance to the parties as to how they should proceed."
As well as dealing with the issue of Garda evidence, Mr Justice Morgan stressed that allowing the case to slip back from its start date was not an option.
"We are now less than two months away from the commencement of the trial.
"These proceedings were issued in August 2001 and I consider that any risk of further delay is unacceptable."