Complaints of miscarriage of justice as judge takes just two sessions to find defendants guilty of police officer's murder

A judge in southern Egypt has taken just two court sessions to sentence to death 529 supporters of Mohamed Morsi for the murder of a single police officer.

Sixteen people were acquitted after lawyers said they had not been allowed to present a proper defence before the judgment was made.

The defendants were arrested last August during a wave of unrest in which supporters of the former president react violently to the clearance of a pro-Morsi sit-in in Cairoduring which more than 900 people were killed. In addition to the murder, the 529 were accused of attempting to kill two other police officers and attacking a police station.

The death sentences are not final and appeals are likely; similar sentences have often been commuted in Egypt. But families of the accused and rights lawyers described the process as a miscarriage of justice.

One man, whose father was among those sentenced to death, said: "Nothing can describe this scandal. This is not a judicial sentence, this is thuggery."

He added: "The session last[ed] for five minutes, [and] during those five minutes none of the lawyers or the defendants were listened to – not even the prosecution. The judge just came in to acquit [the 16] and sentence to death the others."

Mohamed Zaree, head of the Cairo Institute for Human Rights Studies (CIHRS), a prominent rights group, said: "This verdict is a disaster. To rule in the second session of a trial – it means the judge didn't hear the defence or look at the evidence. Even someone from the second grade of the law faculty would never have issued this verdict – it goes against the basic principles of criminology."

The same court will try 683 more Brotherhood supporters on Tuesday – including the leader of the group, Mohamed Badie, and the head of its political wing, Saad al-Katatny.

The defendants are among at least 16,000 political dissidents arrested since the overthrow of Morsi last July, according to police figures. Some rights groups say the real figure may be as high as 23,000, and many of those imprisoned have been tortured by the authorities.

One of the most high-profile detainees – Alaa Abd El Fatah, a secular activist investigated by every regime since Hosni Mubarak – was released on bail on Sunday in a rare instance of judicial clemency.

Additional reporting by Manu Gallad