The chief prosecution witness in the trial of Mr Michael McKevitt will begin his evidence today.
Mr Rupert, who is living in the United States under a false identity, began spying for the FBI in 1994, and later for the British security service and the Garda.
The court has also heard he recently entered into a deal in the United States for a book on his experiences.
Mr McKevitt is charged with directing terrorism and being a member of an illegal organisation.
