The man known only as Witness K is expected to plead guilty at the start of the three-day hearing.

He is accused of breaching national security laws after exposing the Australian government's bugging of the East Timorese cabinet room in 2004, as the two countries negotiated an oil deal.

Ahead of the hearing, the court will decide in March how to deal with confidential information under national security laws.

The ABC will also make an an appearance at the March hearing where they're expected to argue for an open court.

Witness K's lawyer Haydn Carmichael tried to have an affidavit lodged by the federal attorney-general thrown out during a brief procedural hearing at the ACT Magistrates Court on Friday.

However the effort was shot down, with Acting Chief Magistrate Glenn Theakston describing the affidavit as vanilla and obtuse.

Mr Carmichael, who is working pro bono, also repeated his previous criticism of Legal Aid for their delays in funding Witness K's defence and bringing witnesses from overseas.

Witness K's former lawyer, Bernard Collaery, is also facing charges for his role in helping reveal the scandal.

Collaery is expected to fight the charges in the ACT Supreme Court.

Australian Associated Press