The only man convicted of a Co Tyrone pub bombing linked to a loyalist unit behind more than 100 murders named alleged accomplices, the High Court has heard.
Counsel for the brother of a teenager killed in the St Patrick's Day attack on the Hillcrest Bar 40 years ago argued there is now fresh evidence in a case involving suspected state collusion.
The claim was made during a legal action against the PSNI for failing to complete an overarching review of the activities of the so-called Glenanne gang.
A draft report by the now defunct Historical Enquiries Team (HET) into alleged security force collaboration with the killers was 80% finalised before being shelved, a judge was told.
Judicial review proceedings have been brought in the name of Edward Barnard.
Mr Barnard's 13-year-old brother Patrick was one of four people killed in the Hillcrest Bar bombing in Dungannon on 17 March, 1976.
Five years later Dungannon UVF member Garnet James Busby was convicted after admitting his role in the attack.
The murder gang based at a farm in Glenanne, Armagh allegedly contained members of the Royal Ulster Constabulary and the Ulster Defence Regiment.
Up to 120 murders in nearly 90 incidents in Mid Ulster and Irish border areas are under scrutiny.
They include outrages such as the 1975 Miami Showband Massacre, where three members of the popular group were taken from their tour bus and shot dead on a country road in Banbridge, Co Down, and the Step Inn pub bombing in Keady a year later, which claimed the lives of two Catholics.
More than 40 bereaved relatives packed into the High Court in Belfast to hear continuing legal submissions.
With the HET now shut down, Mr Barnard wants a judge to compel police to complete the full investigation and publish the findings.
The court heard he now has access to the unfinished review but has not examined it to ensure he remains in the same position at the other families.
His barrister, Danny Friedman QC, said documents in the case revealed Busby named two other suspects who allegedly took the bomb to the bar.
"My client has access to, and we on his behalf have access to (material) to say fresh evidence is available," he argued.
"In human rights terms, the product that my client now has available to him puts him in the position to say there must be an official gathering of available information that is not only relevant to potential criminal justice but to other available rule of law remedies, be they civil, administrative or disciplinary."
Earlier, counsel for the Chief Constable argued that it would be an unnecessary step to force police to finalise an overarching report that has yielded no new investigative opportunities.
He also questioned the quality of the unfinished work he described as "stitching together" individual case reviews.
Tony McGleenan QC said: "The applicant's case is that Article 2 (of the European Convention on Human Rights) requires the court to order the Chief Constable to complete a report which he thinks is a shoddy and unsatisfactory piece of work."
Mr McGleenan also cited the significant significant demands on police resources from other murder investigations.
Mr McGleenan added: "This particular challenge is pursuing a fruitless endeavour in attempting to complete a piece of work that will not deliver anything meaningful for the Barnard family at all.
"That doesn't mean there aren't questions to be answered to some public forum."
The hearing continues.