The British lawyer Gareth Peirce, famed for helping free the Guildford Four and Birmingham Six, will represent John Downey, who is accused for killing four British soldiers in the IRA 1982 Hyde Park bombings.
Downey (61), from Donegal, will stand trial in November. He is charged with the deaths of the four soldiers and causing the explosion. He is charged with murdering Roy John Bright, Dennis Richard Anthony Daly, Simon Andrew Tipper and Geoffrey Vernon Young.
Peirce is known most recently for representing the radical cleric, in Britain, Abu Qatada. She also represents Julian Assange the editor-and-chief of WikiLeaks. She is known for her high-profile cases involving miscarriages of justice and those people accused of Irish and Islamist terrorism.
Downey was arrested last month as he disembarked a plane from Ireland arriving in Gatwick.
Irish politicians including West Tyrone MP Pat Doherty are calling for Downey to be released and returned home as they believe his arrest was in violation of the Good Friday Agreement.
Downey is charged with causing one of two nail bomb blasts that took place in central London on July 20, 1982. Eleven people were murdered in IRA attacks that day.
At the Mall road the four soldiers who died were members of the Royal Household Cavalry. They were on their way to Buckingham Palace, from their barracks in Knightsbridge when a blue Austin car exploded.
Two hours later another seven people were killed and 50 injured in a second explosion at Regent's Park bandstand which killed seven Royal Green Jackets bandsmen.