Speaking before the US Congressional Helsinki Committee, which investigates human rights abuses around the world, Judge Peter Cory recommended a public inquiry into four controversial killings.
The judge first began investigating suspicious murders in Northern Ireland following the Weston Park Agreement.
In the agreement, the British and Irish governments recognised that "certain cases from the past remain a source of grave public concern".
But one of the most shocking allegations to surface during the investigation was that of cooperation between British intelligence and anti-nationalist paramilitary groups.
The hearing will likely recommend public inquiries and consider what action London should take in response to Cory's recommendations.
Geraldine Finucane, the widow of murdered human rights lawyer Pat Finucane, will also testify and is expected to call for an immediate public inquiry into the loyalist murder of her husband.
Irish Republicans protest on the
steps of MI5 building in London
All four murders took place in Northern Ireland. Finucane was shot in his home in 1989.
Construction worker Robert Hamill was kicked to death in 1997 in Portadown. Dissident loyalist leader Billy Wright was murdered in Maze prison in 1997 and lawyer Rosemary Nelson was blown up in a car bomb in 1999.
When the British Government first released Cory's report on 1 April, it drew sharp criticism from nationalists for failing to set a date for an inquiry into Finucane's murder.
However, London said it was waiting for the end of the trial of Ken Barrett, a loyalist accused of the murder.
The US Helsinki Commission is an independent federal agency which encourages progress in implementing provisions of the Helsinki Accords.