The defence team for prominent activist Alaa Abdel-Fattah and 24 others has filed a motion requesting that the head judge be removed on the grounds that he is biased against the defendants.
The motion cited Abdel-Fattah's well-known opposition to the 2005 parliamentary elections and subsequent accusations of fraud head of the trial in which the activists stand accused of illegal protesting.
The trial was postponed on Sunday to 10 May to allow for the defence's motion to be examined.
Abdel-Fattah and his co-defendants face charges related to a protest against military trials for civilians, held outside the Shura Council in November last year.
It was one of the first protests forcibly dispersed by security forces in accordance with a controversial new protest law that criminalises unauthorised public demonstrations.
The No to Military Trials campaign claimed responsibility for organising the protest, but Abdel-Fattah was charged with being its organiser.
Abdel-Fattah was also charged with assaulting security personnel and stealing a police officer's two-way radio.
All the defendants have been released on bail.