The leading Bahraini human rights and political activist, Abdulhadi al-Khawaja, has appeared in court in the capital, Manama, for his retrial.
Mr Khawaja, who began a hunger strike in February in protest at the prison sentence he was given by a military court in June, was in a wheelchair.
The AFP news agency said he looked weak but moved his chair without assistance.
Mr Khawaja and 20 others are accused of plotting to overthrow the state. Seven of them are being tried in absentia.
The defendants were convicted by the National Safety Court, a military tribunal. Seven of them, including Mr Khawaja, were sentenced to life.
But in April, Bahrain's highest court, the Court of Cassation, threw out their convictions and ordered a retrial, although they were not released.
The retrial began at a civilian court in Manama on 8 May, but it was adjourned until Tuesday because Mr Khawaja and Abdullah al-Mahroos, a prominent Shia religious figure and critic of the Sunni-dominated government, were too ill to attend.
On Tuesday, Mr Khawaja was taken from his room at the Bahrain Defence Force Hospital to the court in a wheelchair by a doctor and two nurses, his wife Khadija al-Mousawi wrote on Twitter.
An AFP correspondent said Mr Khawaja looked frail and weak, but moved his chair forward without medical assistance.
"The continuation of my arrest is a crime," Mr Khawaja told the court, according to AFP. "Stop this sham trial.
"There is no legal excuse for my continued detention.
"For more than 100 days I have been on hunger strike and am ready to sacrifice my life to demand freedom," he said, adding he had been "force-fed" in prison.
Mrs Mousawi said her husband had also told the court about the torture he was subjected to after being detained in April 2011, a month after the authorities violently suppressed a mass pro-democracy demonstration at the now-demolished Pearl Roundabout.
"There was a moment of silence when he spoke about the psychological torture when they lied to him about arresting [their daughter] Zainab... torturing, raping Zainab and moving her to a jail in Saudi Arabia. This must have been harder than the torture itself," she wrote.
Mrs Mousawi said her husband's trial was later adjourned until 29 May.
In a separate development, another court adjourned until 27 May a hearing in the case of Zainab al-Khawaja, who was arrested a month ago after she staged a lone protest on a motorway against the imprisonment of her father during the Formula 1 Grand Prix.
Ms Khawaja has been charged with disrupting the traffic and insulting a police officer.
At least 60 people are said to have been killed since protests erupted in February 2011, demanding more democracy and an end to discrimination against the majority Shia Muslim community by the Sunni royal family.
King Hamad has tried to address some of the protesters' demands by announcing constitutional reforms intended to lead to greater accountability.
But the opposition, as well as human rights groups, say the promises are empty and that the crackdown on dissent is continuing.
The UN Human Rights Council on Monday urged Bahrain to release all political prisoners, including Mr Khawaja and Nabeel Rajab, who is being held on charges of inciting protests by using social networking websites.