After months of delays, a military court resumed Monday the case against September 11th mastermind Khalid Sheikh Mohammed and four co-defendants.
Hearings on pretrial motions, which are expected to last all week, began at the Guantanamo Bay Naval Base in Cuba.
Monday's agenda included courtroom security rules the defense claims are too restrictive.
The group has not been in court since May when they refused to cooperate at their arraignment and at times stood up during the trial to pray.
Their trial is not expected to begin until next year.
Victims' relatives, survivors and first responders are being allowed to watch the proceedings on closed circuit television at several locations, including Fort Hamilton in Brooklyn.