A high court judge has criticised the police for not disclosing documents in an alleged collusion case about the Miami Showband murders in 1975.
Three members of the band were killed by loyalists in a bomb and gun attack when their bus was stopped near Newry.
Victims of the attack are suing the Ministry of Defence (MOD) and Police Service of Northern Ireland (PSNI).
They say there was collaboration between the killers and serving soldiers.
On Friday, Justice Maguire said delays in receiving the material from the PSNI were “appalling” and he warned he may strike out their defence to the claim.
He said: “This case has been going on since 2012, and we are at a stage in 2020 where the obligation of discovery on the police service has not been complied with.
“The court seems to be getting the runaround. It makes me angry (and) shows so much disrespect to the court.”
The attack in July 1975 happened as the band, which toured across Ireland, were travelling home to Dublin after a gig in Banbridge.
Their minibus was stopped by a fake army patrol involving Ulster Defence Regiment (UDR) and Ulster Volunteer Force (UVF) members.
The band was made to stand by the roadside while a bomb was placed on the bus.
It exploded prematurely, killing two of the attackers, Harris Boyle and Wesley Somerville.
The rest of the gang opened fire, murdering three members of the band, singer Fran O’Toole, guitarist Tony Geraghty and trumpeter Brian McCoy.
Two other band members, Des McAlea and Stephen Travers, were injured but survived.
In 2011, a report by the Historical Enquiries Team raised concerns about collusion around the involvement of an RUC Special Branch agent.
It found that mid-Ulster UVF man Robin Jackson claimed in police interviews he had been tipped off by a senior RUC officer to lie low after his fingerprints were found on a silencer attached to one of the weapons.
He was later acquitted on a charge of possessing the silencer.
Two UDR soldiers were convicted for their roles in the attack.
The victims’ case has alleged that military chiefs knew about paramilitaries infiltrating the UDR, but failed to stop it.
Damages are being sought in writs against the MOD and the PSNI Chief Constable for assault, trespass, conspiracy to injure, negligence and misfeasance in public office.
Some army files have been disclosed to the plaintiffs, however, they were redacted on national security grounds.
A barrister representing Chief Constable Simon Byrne said “administrative problems” were to blame for the delay in submitting documents and asked for two weeks to arrange any application for Public Interest Immunity.
Justice Maguire ruled there would be a two-week adjournment, but said: “I would be inclined to consider seriously striking out the police defence”.
“I think the time is coming in this case where the court’s patience is (running out).”