A public inquiry into the Omagh bombing is needed to learn lessons from any failures in the state’s system for protecting against terrorist threat, the High Court has heard.
Counsel for the father of one of the victims also claimed such a probe was required to establish whether the atrocity could have been thwarted.
Michael Gallagher’s son Aiden was among 29 people, including a woman pregnant with twins, killed in the August 1998 Real IRA attack.
Mr Gallagher is challenging the government’s refusal to hold a public inquiry into the outrage.
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 bombing.
Hugh Southey QC, for Mr Gallagher, told the court the efficiency of measures put in place to protect life needs to be investigated.
“It’s clear in August 1998 there was a known risk to the people of Northern Ireland from dissident republicans,” he said.
“What is now alleged at the heart of this case is that the system (to address that risk) didn’t operate as efficiently or effectively as it should have done.
“That’s why Article 2 (of the European Convention on Human Rights) requires an investigation.
“If that system was not as efficient as it should have been there’s a need to learn lessons.”
Mr Gallagher launched his legal action after former Northern Ireland secretary of state Theresa Villiers rejected calls for a public investigation back 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 outrage.
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.
The challenge had been delayed due to issues over holding partially closed hearings to protect national security.
As the public hearing resumed, Mr Southey pointed to the views of a former ombudsman, Baroness Nuala O’Loan, that the bombing could have been prevented.
He told Mr Justice Horner that Special Branch officers were reluctant to cooperate with a previous probe, and claimed failures in how they dealt with David Rupert, the FBI spy who infiltrated dissident republican ranks.
“There are real questions about whether or not they should have responded differently,” counsel said.
“On the face of the open material Mr Rupert’s handlers appeared to do nothing with this intelligence.”
The case continues.