A man in his 70s is due before the Special Criminal Court this afternoon charged in connection with the murder of Denis Donaldson in 2006.
The Sinn Féin official was shot dead at his home in Cloghercor, Co Donegal in April 2006.
It was shortly after it had been revealed that he'd worked as a British intelligence agent.
A second man in his 40s was arrested in relation to the murder but has been released without charge.
The two men were arrested on Tuesday and had been detained in Letterkenny Garda Station for questioning.