The Police Ombudsman is investigating claims that the RUC failed to prevent a murder attempt on Sinn Fein president Gerry Adams more than 20 years ago.
Mr Adams has made a complaint following reports that the police had prior knowledge of a UDA plan to ambush him in Belfast city centre in March 1984 while he was travelling from the High Court.
Mr Adams was shot five times when his car was sprayed with bullets, while his bodyguards were also seriously injured.
UDA leader John Gregg was jailed for his part in the shooting.
There have long been questions about how the UDA gang knew the date of Mr Adams' court hearing.