A new investigation has been launched into allegations that police officers may have contributed to the death of republican informer Denis Donaldson.
The Police Ombudsman has overturned a previous decision by his office to close the investigation and declare there was no misconduct by officers.
The senior Sinn Fein official was shot dead in outside Glenties in April 2006.
He had gone into hiding after police told him the media were preparing to expose his secret life as an informer.
The Real IRA said it was responsible but his family alleged that police officers may have exposed him as an agent and contributed to his death.
Three years ago the Police Ombudsman at the time, Al Hutchinson, said there had been no police misconduct and declared the case closed.
But a BBC Spotlight investigation in October 2011 revealed investigators had not interviewed a special branch officer who Mr Donaldson’s family believe may hold vital information about what happened.
They were also unaware he had been writing a journal which his family believe could contain clues about who killed him and why.
The current ombudsman, Michael Maguire, confirmed on Wednesday that he has launched a new investigation.
It is understood investigators will seek access to the journal, which was removed by Garda officers investigating the killing, and to interview the special branch officer.
Mr Donaldson was shot at a remote cottage in Glenties in 2006.
He moved out of his Belfast home a few months before his death, and had been living in the run-down cottage which had neither electricity nor running water.
Four months earlier, he had been expelled from Sinn Fein after admitting being a paid British spy for 20 years