Relatives of those murdered by a notorious loyalist gang that included rogue security force members have hailed a court judgment heavily criticising a police investigation into the collusion claims.
A judge in Belfast ruled that the police's failure to conduct an overarching examination of the extent of state collusion with the Glenanne gang was inconsistent with its human rights obligations.
The Glenanne gang was a unit of the Ulster Volunteer Force (UVF) that counted renegade police and army personnel among its members.
Operating mostly in Tyrone and Armagh, the gang has been blamed for around 130 sectarian murders during the 1970s and 1980s.
The independent Historic Enquiries Team (HET) had partially completed a probe into the activities of the Glenanne gang before its work was halted by Police Service of Northern Ireland (PSNI) commanders.
The HET had examined individual murders committed by the gang but had not undertaken an overarching thematic review of the collusion allegations.
The PSNI's decision to stop the HET review was challenged by way of judicial review by the family of one of the gang's victims.
Delivering judgment at Belfast High Court, Judge Seamus Treacy found that changes made by the PSNI to how it investigated historic cases were "fundamentally inconsistent" with its obligations in the European Convention on Human Rights.
He said its stance raised concerns among the families about the state's commitment to investigating cases that involved alleged collusion.
He was particularly critical of decisions taken by former PSNI chief constable Sir Matt Baggott.
The judicial review was taken by the family of Patrick Barnard, who was killed in a bomb blast in Dungannon in 1976.
Patrick's brother Edward said he had not expected the outcome.
"I am shocked. I did not think we would get the victory today that we have got," he said afterwards.
"We have proved collusion, we have proved that the police halted the report, they stopped the HET from fulfilling their part."
The court was packed with relatives who lost loved ones at the hands of the murderous gang.
Outside, some wept and others applauded as they reflected on the judgment.
Eugene Reavey, whose three brothers were murdered by the gang in 1976, described the alleged collusion as a "war crime".
"The judge repeated collusion, collusion, collusion all day," he said.
"This was a war crime - there were 135 people dead. This was murder by the state and its agents.
"There is no other word for it than a war crime - that's how big it is.
"I am delighted for everybody here for the perseverance they have shown over the years. We have been humiliated, we have been abused by everybody in every part of the journey but today we have been vindicated."
The judge said the Barnard family had a "legitimate expectation" that a thematic probe into collusion would have been completed.
He said the police's treatment of them had been "unfair" in the "extreme".
"It has completely undermined the confidence of the families whose concerns are not only still unresolved but compounded by the effects of the decisions taken by the then chief constable (Mr Baggott)," he said.
Justice Treacy added: "There is a real risk that this will fuel in the minds of the families the fear that the state has resiled from its public commitments because it is not genuinely committed to addressing the unresolved concerns that the families have of state involvement."
The judge placed the onus on the PSNI to offer an "appropriate form of relief" that would address the family's concerns.
The HET was originally set up in 2006 to fulfil the state's obligations under Article 2 of the ECHR to ensure legacy investigations were independent and effective.
The team was initially operationally independent from the PSNI, with detectives brought in from outside Northern Ireland. Its funding was also ring-fenced from the wider PSNI budget.
This structure was approved by the Council of Europe's Committee of Ministers (CM) in 2009.
But the practices of the HET subsequently altered when Mr Baggott introduced changes that gave the PSNI more involvement in historic cases.
Judge Treacy said this began a process of "dismantling" the approach the Committee of Ministers had signed off on.
He said Mr Baggott's decision to axe the HET in 2014 and bring Troubles investigations back in-house under a new Legacy Investigations Branch (LIB) further undermined the state's undertakings under Article 2.
"The changes in the structure and process introduced after 2009 makes it clear that the structure and process now in place lacks most, if not all, of the essential safeguards which the UK Government agreed with the CM to put in place for future investigations of cases of this nature," he said.
The establishment of the LIB was supposed to be an interim measure, pending the establishment of a new independent investigations body as agreed by the region's politicians in the Stormont House Agreement. However, political impasses at Stormont mean the new legacy mechanisms have yet to be implemented and the LIB still has responsibility for historic probes.
The judge said the failure to complete the Glenanne collusion report meant potential evidential opportunities had been missed.
"The chief constable in halting that process which had been openly promised and which was acknowledged to be essential to the HET's purpose has turned his back on a potentially rich source of evidential opportunities," he said.
"This decision frustrates any possibility of an effective investigation which would fulfil the Article 2 duty which now arises and has foreclosed any possibility that the Article 2 duty will be fulfilled."
Darragh Mackin, solicitor for Mr Barnard, said the families had been through an "excruciating" process.
"This has been a long and turbulent journey for these families," he said.
"Not only has the court today ruled that there is credible evidence (of collusion) throughout the Glenanne series but the procedure and torment that these families have had to go through has been extremely unfair and there has been an abuse of power by the powers-that-be."
In response to the judgment, PSNI Assistant Chief Constable Mark Hamilton, who heads up the service's Legacy & Justice Branch, said: "The PSNI notes the comments made in court today by Mr Justice Treacy in relation to the Judicial Review taken by the family of Patrick Barnard."
Judge Treacy's full written judgment has not been published yet, due to issues around the need to redact some names.
Mr Hamilton added: "We understand that Mr Justice Treacy has not publicly released his judgment but will do so within the next few weeks.
"Once we receive the judgment we will consider it carefully."