A landmark bid for a partially secret court hearing over intelligence gathered on the Omagh bombing is set to get under way next month.
Lawyers for the Government are expected to argue that national security-sensitive material is suitable for an application to hold a closed material procedure (CMP).
The move forms part of a legal challenge to Northern Ireland Secretary of State Theresa Villiers’ refusal to hold a public inquiry into the atrocity.
Michael Gallagher, whose son Aiden was among 29 people killed by the Real IRA bomb in August 1998, is seeking to have her decision judicially reviewed.
The case centres on claims that a range of intelligence from British security agents, MI5 and RUC officers could have been drawn together to prevent the attack.
An alleged gap in the information relates to any monitoring of the bomb and scout cars as they crossed the Irish border into Omagh on the day of the outrage.
But counsel for the Secretary of State are to seek a CMP in advance of the legal challenge being heard in full.
That process, under powers contained in the Justice and Security Act 2013, would examine whether public disclosure of some information would be damaging to national security.
It would involve intelligence documents being assessed by a judge and a special advocate barrister appointed to protect the rights of Mr Gallagher while he is shut out of the hearing.
At the High Court on Friday it was confirmed that the first stage, to decide if the case is suitable for a CMP application, is listed for a two-day hearing next month.
It will be the first such legal bid in judicial review proceedings in Northern Ireland.
Paul McLaughlin, representing the Secretary of State, said a sample of the closed material has been gathered and is being stored at a secure location away from the Royal Courts of Justice.
Asked by Mr Justice Maguire how many documents were involved, the barrister replied: “I would rather not say in open court.”
The judge was also told David Scoffield QC has been appointed as the special advocate to represent Mr Gallagher’s interests.
Mr Scoffield indicated his preference for any non-sensitive documents to be handed over before the CMP proceedings get under way.
“Once I have seen the closed material I’m precluded from communicating with the applicant (Mr Gallagher),” he explained.
The bereaved father launched his legal action after Ms Villiers rejected calls for a public investigation in September 2013.
She decided instead that a probe by Police Ombudsman Michael Maguire was the best way to address any outstanding issues surrounding the atrocity.
In October 2014 Dr Maguire published a report where he found RUC Special Branch withheld some intelligence information from detectives hunting the bombers.
No one has ever been convicted of carrying out the attack, but Seamus Daly, a 44-year-old bricklayer from Cullaville, Co Monaghan, is currently charged with the 29 murders which he denies.
Central to the judicial review challenge is a contention that the Government has a duty under Article 2 of the European Convention on Human Rights to protect lives and investigate the bombing.
The case has been adjourned for a further review later this month.