A High Court judge has ruled the PSNI's failure to conduct an overarching review of state collusion with a notorious loyalist gang breached its human rights obligations.
The independent Historic Enquiries Team (HET) had partially completed a probe into the activities of the Glenanne gang but its work was halted by 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 Patrick Barnard, who was killed in a bomb blast in Dungannon in 1976.
The Glenanne gang was a UVF unit that counted rogue security force personnel among its members.
Primarily operating in Tyrone and Armagh, the gang has been blamed for around 130 sectarian murders during the 1970s and 1980s.
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 also questioned 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 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".
The judge placed the onus on the PSNI to offer an "appropriate form of relief" that would address the family's concerns.