Khalid Sheikh Mohammed, the admitted 9/11 architect, and the four men accused of aiding the conspiracy put off their pleas until a later date. Lawyers were still discussing trial dates Saturday night; another hearing was set for June 12.
Earlier, Mohammed cast off his earphones providing Arabic translations of the proceeding and refused to answer Army Col. James Pohl's questions or acknowledge that he understood them. All five men refused to participate in the hearing.
Walid bin Attash was confined to a restraint chair when he came into court, and was released only after promising to behave.
Ramzi Binalshibh began praying alongside his defense table, followed by Ali Abd al-Aziz Ali, in the middle of the hearing; Binalshibh then launched into a tirade in which he compared a prison official to late Libyan leader Moammar Gadhafi and declared he was in danger.
"Maybe they will kill me and say I committed suicide," he said in a mix of Arabic and broken English.
The detainees' attorneys spent hours questioning the judge about his qualifications to hear the case and suggested their clients were being mistreated at the hearing, in a strategy that could pave the way for future appeals. Mohammed was subjected to a strip search and "inflammatory and unnecessary" treatment before court, said his attorney, David Nevin.
It was the defendants' first appearance in more than three years after stalled efforts to try them for the terror attacks, in which hijackers steered four commercial jets into the World Trade Center, the Pentagon, and a field in Shanksville, Pa. Nearly 3,000 people were killed.
A handful of people who lost relatives in the attacks and who were selected by lottery to attend the proceedings watched in the courtroom.
The Obama administration renewed plans to try the men at the U.S. base at Guantanamo Bay after a bid to try them in New York City blocks from the trade center site ran into political opposition. It adopted new rules with Congress that forbade testimony obtained through torture or cruel treatment, and officials now say the defendants could be tried as fairly at Guantanamo as in a civilian court.
Human rights groups and defense lawyers say the secrecy of Guantanamo and the military commissions, or tribunals, will make defending the men impossible. They argued that the United States kept the case out of civilian court to prevent disclosure of the treatment of prisoners like Mohammed, who was waterboarded 183 times.
Nevin said he thought Mohammed was not responding because he believed the tribunal was unfair. Jim Harrington, representing Binalshibh, said his client would not respond to questions "without addressing the issues of confinement."
Cheryl Bormann, a civilian attorney for bin Attash, appeared in a conservative Islamic outfit that left only her face uncovered, and she asked the court to order other women present to wear "appropriate" clothing so the defendants did not have to avert their eyes "for fear of committing a sin under their faith."
Pohl warned that he would not permit defendants to block the hearing and would continue without their participation.
"One cannot choose not to participate and frustrate the normal course of business," he said.
Pohl brought translators into the courtroom to interpret the proceedings when the men refused to use earpieces. He tried to stick to the standard script for tribunals, asking the defendants whether they understood their rights to counsel and would accept the attorneys appointed for them.
The men remained silent.
During the failed first effort to prosecute the men at the U.S. base in Cuba, Mohammed mocked the tribunal and said he and his codefendants would plead guilty and welcome execution. But there were signs that at least some of the defense teams were preparing for a lengthy fight, planning challenges of the military tribunals and the secrecy shrouding the case.
Defendants typically do not enter pleas during arraignment but are offered the chance to do so.
Army Capt. Jason Wright, one of Mohammed's Pentagon-appointed attorneys, declined to comment on the case.
Attorney General Eric H. Holder announced in 2009 that Mohammed and his codefendants would be tried blocks from the site of the destroyed trade center, but the plan was shelved after New York officials cited huge costs to secure the neighborhood and family opposition to trying the suspects in the United States.
Congress then blocked the transfer of any prisoners from Guantanamo to the United States, forcing the Obama administration to refile the charges under a re-formed military commission system.
Mohammed, a Pakistani citizen who grew up in Kuwait and attended college in Greensboro, N.C., has admitted to military authorities that he was responsible for the 9/11 attacks "from A to Z," as well as about 30 other plots, and that he personally killed Wall Street Journal reporter Daniel Pearl. Mohammed was captured in 2003 in Pakistan.
Binalshibh was allegedly chosen to be a hijacker but couldn't get a U.S. visa and ended up providing assistance such as finding flight schools. Bin Attash, also from Yemen, allegedly ran an al-Qaeda training camp in Afghanistan and researched flight simulators and timetables.
Mustafa Ahmad al-Hawsawi is a Saudi accused of helping the hijackers with money, Western clothing, traveler's checks, and credit cards. Al-Aziz Ali, a Pakistani national and nephew of Mohammed, allegedly provided money to the hijackers.