Cairo (CNN) -- Hosni Mubarak should be tried by a special tribunal because he is still president of Egypt and did not sign an official resignation, his lawyer said Sunday.
"He gave up the presidency orally to former vice-president Omar Suleiman without signing any official document, which is not legal by the constitution," lawyer Farid El Deeb said.
The court proceedings were recounted to CNN by civil rights lawyer Khaled Abu Bakr, who attended the hearing.
A former head of an Egyptian lawyers' organization said Mubarak is not the president.
"The revolution revokes the constitution," Zakaria Abdel Aziz said. "The Egyptian people said their word ... this is a nation that had a vice president at the time and this is an ousted president."
The trial was adjourned until Monday, when lawyers will start their defense of the former interior minister, who faces charges with Mubarak and his sons.
Last week, El Deeb called for Mubarak to be tried in a military court, saying military law dictates that he is still the head of the Egyptian air force.
Mubarak is accused of corruption and ordering protesters killed during the country's uprising that brought his 30-year rule to an end in February.
He has denied the charges.
Two of Mubarak's sons are also on trial on a variety of charges. The sons, Gamal and Alaa, have pleaded not guilty.
Amnesty International had estimated more than 840 protesters were killed and 6,000 injured. A prosecutor's spokesman cited 225 people killed and more than 1,300 injured, saying the number is lower because there is a difference between those killed while attacking police stations and those shot while protesting.