Northern Ireland's Attorney General wrongly refused to order a new inquest which could find out who was to blame for police failures around a deadly IRA bombing, the High Court has heard.
In an unprecedented move, John Larkin QC is facing legal action for deciding against holding fresh tribunals into the so-called 'Good Samaritan' attack that killed three Londonderry neighbours 27 years ago.
Lawyers for one of the victim's families claimed an obligation to re-examine the deaths has been revived by a Police Ombudsman report. It found the RUC had information about the planned terrorist strike but did not alert residents to the danger.
The Ombudsman said while responsibility for the deaths rested with the people who planted the bomb, police had failed to protect the victims and the subsequent murder investigation was flawed, inadequate and incomplete.
It was argued that the Attorney General wrongly and irrationally concluded there would be no benefit in ordering a new inquest.
Barrister Fiona Doherty QC also claimed at least eight significant police witnesses had refused to co-operate with the watchdog.
She told Mr Justice Maguire: "The purpose of holding this inquest is not solely to establish an historical truth, but the establishment of responsibility."
It is the first case of its kind to challenge the decision-making powers of Northern Ireland's chief legal officer.
Proceedings have been brought by Dorothy Johnstone, whose 54-year-old father Eugene Dalton died in the August 1988 booby-trap bombing.
Sheila Lewis (68) was also killed in the explosion at a house in the city's Creggan area.
A third victim, 57-year-old Gerard Curran, died months after being pulled from the rubble.
The attack became known as the 'Good Samaritan bomb' because the three friends had gone to check on the whereabouts of a neighbour kidnapped earlier by the IRA.
Mr Dalton climbed through a window, and just as he was about to open the front door to Mrs Lewis and Mr Curran, the bomb went off, collapsing the roof and wrecking three external doors.
All three victims were Catholics.
The IRA later apologised, admitting it planted the booby trap bomb inside a Wellington boot in the flat's hallway in a bid to kill soldiers.
In 2013 Police Ombudsman Dr Michael Maguire published findings that RUC officers had information about an IRA booby trap bomb in a house in the housing estate but did nothing to warn residents of the possible danger.
He identified a failure in the police obligation to protect the lives of the public.
Seeking leave to apply for a judicial review, Ms Doherty argued that investigative obligations under Article 2 of the European Convention on Human Rights were rekindled by the Ombudsman's findings.
She identified key pieces of intelligence, claiming police inquiries carried out at the time were ineffective. The original inquest was "relatively perfunctory", the barrister submitted.
Ms Doherty also claimed the Ombudsman's probe had been hampered by a lack of co-operation.
"What the report doesn't do, and what it can't because of the limitations on the powers of the Police Ombudsman, is to investigate properly and allocate responsibility," she told the court.