They knelt in prayer, ignored the judge and would not listen to Arabic translations as they confronted nearly 3,000 counts of murder.
The self-proclaimed mastermind of the September 11 attacks and four co-defendants defiantly disrupted an arraignment that dragged into Saturday night in the opening act of the long-stalled effort to prosecute them in a military court.
More than seven hours into the hearing, the judge at the US military base in Cuba had not yet read the charges against the men, including 2,976 counts of murder and terrorism in the 2001 attacks that sent hijacked jetliners into New York's World Trade Centre and the Pentagon.
Khalid Sheikh Mohammed, the admitted 9/11 architect, and the four men accused of aiding the 9/11 conspiracy put off their pleas until a later date.
Earlier, Mohammed cast off his earphones providing Arabic translations of the proceeding and refused to answer Army Colonel James Pohl's questions or acknowledge he understood them. All five men refused to participate in the hearing; two passed around a copy of The Economist magazine and leafed through the articles.
Walid bin Attash was confined to a restraint chair when he came into court, released only after he promised to behave. Ramzi Binalshibh knelt in prayer alongside his defence table with Ali Abd al-Aziz Ali in the middle of the hearing, then launched into an incoherent tirade about the late Libyan leader Muammar Gaddafi 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' lawyers 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 Centre, the Pentagon and a western Pennsylvania field. Nearly 3,000 people were killed.
In the past, during the failed first effort to prosecute them at the US base in Cuba, Mohammed has mocked the tribunal and said he and his co-defendants would plead guilty and welcome execution. But there were signs that at least some of the defence teams were preparing for a lengthy fight, planning challenges of the military tribunals and the secrecy that shrouds the case.
Defendants typically do not enter a plea during their arraignment but are offered the chance to do so. Lawyers for the men said they were prohibited by secrecy rules from disclosing their clients' intentions.