Bloemfontein - Treason accused and rightwinger Johan Prinsloo closed his defence without presenting any further testimony or evidence in the Bloemfontein High Court on Monday.
Johann Nel, for Prinsloo, told the court the defence decided to close its case after much debate.
Prosecutor Torie Pretorius closed the State's case on Thursday and the matter was postponed to Monday.
Prinsloo, 51, of Springs in Gauteng, faces charges of treason, conspiracy to take part in terrorist acts, and possession of illegal ammunition.
Prinsloo, Martin Keevy, 49, and Mark Trollip, 48, were arrested for an alleged plot to attack the African National Congress's Mangaung conference at the University of the Free State in Bloemfontein in December 2012.
The State alleges Prinsloo tried between July 2012 and December 16, 2012 to overthrow the government by trying to obtain mortar bombs and other weapons to attack President Jacob Zuma and Cabinet ministers during the conference. He has pleaded not guilty to all the charges.
On Monday, Judge Mojalefa Rampai postponed the matter to September 22 for the parties to start final arguments.
Trollip pleaded guilty to a charge of conspiracy and was sentenced to eight years' imprisonment last year. Keevy was declared unfit to stand trial.