The trial relating to an alleged plot to assassinate former conservative prime minister Costas Karamanlis started on Friday but was adjourned until May 14.
This came a day after leaked intelligence service documents claimed there was no evidence of such a plan.
The trial will proceed without a key defendant as a prime suspect in the alleged plot identified as William B and named in confidential documents was never traced.
The former PASOK MP Michalis Karchimakis has been added as a defendant over a document that was found in his possession.
Karchimakis had been cleared of any links to the affair but, according to a prosecutor, his acquittal was based on an incomplete case file.