But "I don't think anyone is going to plead guilty," said Jim Harrington, Binalshibh's civilian lawyer, who added the defendants are expected to fight the charges against them, which include murder and terrorism and carry a potential death penalty.
Harrington declined to say what would be the basis of his defense, and lawyers for Mohammed did not respond to messages seeking comment.
The men, held in a secret prison in Guantanamo that is under such tight security even its exact location on the base is classified, have not been seen in public since a pretrial hearing the day after Obama's Jan. 21, 2009, inauguration.
Their arraignment comes more than three years after the Obama administration's failed effort to try the suspects in a federal civilian court and close the prison at the U.S. base in Cuba. 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 in Manhattan, 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.
Six family members who won a lottery to attend the proceedings will face Mohammed and the other men in court; others were watching on closed-circuit video at military bases in the United States.
Cliff and Christina Russell traveled from their Rockaway Beach neighborhood in New York to honor the memory of Cliff's younger brother, Stephen, a firefighter killed responding to the attacks. Cliff Russell said he hopes the tribunal will end with the death penalty for Mohammed and his codefendants.
The men never entered formal pleas in previous hearings, but Mohammed had told the court that he would confess to planning the attacks and hoped to be a "martyr."
The arraignment is expected to be followed by a hearing on defense motions that challenge the charges and extreme secrecy rules imposed to prevent the release of information about U.S. counterterrorism methods and strategy.
The American Civil Liberties Union filed a motion Friday asking the judge to prohibit the government's use of a 40-second delay and a white noise machine to prevent any spectators from hearing classified information, including details about the harsh treatment in the secret CIA detention sites overseas.