Judgment has been reserved in a legal bid by the chief constable to overturn a ruling that police in Northern Ireland unlawfully frustrated any chance of an effective probe into a series of killings by the loyalist Glenanne Gang.
George Hamilton is appealing an order compelling him to complete an overarching investigation into suspected state collusion with the group linked to more than 100 murders during the 1970s.
Three senior judges, led by Lord Chief Justice Sir Declan Morgan, confirmed they will take time to assess all legal arguments before delivering their verdict.
Last year the High Court held that victims families were denied in their legitimate expectation that the now-defunct Historical Enquiries Team (HET) would publish a thematic report into the Glenanne Gang’s deadly attacks.
The verdict was reached in a legal challenge brought in the name of Edward Barnard.
Mr Barnard’s 13-year-old brother Patrick was among four people killed in a St Patrick’s Day bombing at the Hillcrest Bar in Dungannon in March, 1976.
Five years later Dungannon UVF member Garnet James Busby received a life sentence after admitting his role in the no-warning attack and other terrorist offences.
The murder gang based at a farm in Glenanne, Co Armagh allegedly contained members of the RUC and the UDR.
Up to 120 murders in nearly 90 incidents in Mid Ulster and Irish border areas are under scrutiny.
Sir Declan, who heard the case with Lord Justice Stephens and Mrs Justice Keegan, will examine submissions and give judgment at a later date.