He was killed by UDA gunmen at his home in 1989
The widow of murdered Belfast solicitor Pat Finucane is to bring an appeal for a public inquiry to the UK Supreme Court.
Geraldine Finucane has been granted permission to appeal against a decision by the Court of Appeal.
Mr Finucane represented IRA hunger strikers and was killed in front of his family by Ulster Defence Association (UDA) gunmen at his home in February 1989.
The Finucane's say former British Prime Minister David Cameron reneged on a commitment, given to their family, for a public inquiry into the circumstances of his murder.
Mrs Finucane appealed against a 2015 judicial ruling that the decision taken by Mr Cameron in 2011 was lawful.
Peter Madden, of Madden & Finucane Solicitors, said: "The only way that the full truth about Pat’s murder can be firmly established, and the extent to which a policy of extra-judicial assassination of which Pat was a victim was authorised by government is by a full transparent public inquiry where witnesses and documents are subject to intense scrutiny.
"We will seek to persuade the Supreme Court at the hearing of this appeal that David Cameron acted unlawfully in refusing a public inquiry and that the Court should quash his decision."
A report carried out by barrister Desmond da Silva in 2012 found that employees of the British State and State agents played a key role in his murder.
The report found there was no "over-arching State conspiracy to murder Patrick Finucane".
But Mr da Silva said: "I am left in significant doubt as to whether Patrick Finucane would have been murdered by the UDA in February 1989 had it not been for the different strands of involvement by elements of the State".
He added: "I believe that it is likely that an RUC officer or officers did propose Patrick Finucane, along with at least one other individual... as a target".