Anthony McKiernan’s murder in 1988 was linked to the army’s most prized asset within the Provisionals, who operated under the codename Stakeknife.
West Belfast man Freddie Scappaticci has denied being the spy said to have headed up the IRA’s internal security unit, known as the Nutting Squad.
At the High Court on Monday lawyers for McKiernan’s family began attempts to secure any report from a re-examination of the case completed in 2012 by the now-defunct Historical Enquiries Team (HET).
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Barrister David Heraghty argued there is a legal obligation to provide material to the next of kin, claiming the current four-year delay amounted to a “public law wrong”.
He told Mr Justice Maguire: “The subject matter of this claim concerns a right of information to a family who have suffered the murder of a loved one, organised and perpetrated by a suspect who is alleged to be acting at the time as a state agent.”
Mr McKiernan, from the Markets area of south Belfast, was killed in January 1988 before his body was found dumped in the west of the city.
An inquest heard the amount of alcohol in his system alone would have been fatal, but he had also been shot in the head.
His family have long maintained that he was not an informer and that he was murdered as a scapegoat.
He had reportedly arranged to meet Scappaticci hours before he was executed.
In 2003 Scappaticci fled Northern Ireland after he was named in the media as being Stakeknife.
Before quitting his home, however, he vehemently denied being the agent now said to be linked to up to 50 murders.
In October last year Director of Public Prosecutions Barra McGrory QC called for police to examine Stakeknife’s activities, along with what was known by RUC Special Branch and MI5.
Chief Constable George Hamilton has since decided detectives from an external force should handle an inquiry which could last five years and cost up to £35 million.
The HET’s re-examination of the McKiernan killing is to be included in that new probe.
According to Mr Heraghty that will compound the years of delay endured by the family.
Amid confusion about whether the HET ever produced a review summary report in the case, he claimed Mr McKieran’s family have been provided with no information.
But Mr Justice Maguire stressed that the death, along with wider activities of the IRA Nutting Squad, remains subject to police scrutiny.
He pointed out: “Mr Scappaticci, to my knowledge, has not been made subject to any charges.
“While folklore has it that he was a central figure to many murders in the enforcement of IRA discipline that’s folklore.
“The point of it is at the moment there’s a live investigation into Mr Scappaticci and his (alleged) activities.”
The judge also questioned the right to access files from an ongoing police inquiry, adding that he could be “besieged” by similar litigation if he allows the bid for a judicial review to proceed.
It was disclosed that at least 40 so-called legacy cases are currently before the High Court.
Counsel for the PSNI emphasised that there is no HET review summary report of the McKiernan probe.
He acknowledged that correspondence erroneously indicating such a dossier was sent to the Police Ombudsman had created confusion.
On that basis Mr Justice Maguire adjourned proceedings for an affidavit from a senior police officer to clarify the position.