A federal appeals court on Thursday temporarily halted a guilty plea hearing for the man accused of masterminding the Sept. 11 attacks while it considers whether the deal he reached to avoid a death-penalty trial remains valid.
The U.S. Court of Appeals for the District of Columbia Circuit issued the order on the eve of a hearing at the U.S. military court at Guantánamo Bay in which a military judge was to question the accused plotter, Khalid Shaikh Mohammed, about the settlement he reached this summer with military prosecutors.
The court will decide, during the next administration, whether Defense Secretary Lloyd J. Austin III successfully withdrew from the settlement on Aug. 2, two days after the retired Army general he put in charge of the case signed it. Two lower, military courts ruled that he had acted too late.
The court also halted plea hearings, scheduled for later this month, that Mr. Austin had wanted stopped for Walid bin Attash and Mustafa al-Hawsawi, two men who were accused of conspiring with Mr. Mohammed in the attacks.
The back and forth over the settlement has caused anguish for relatives of the nearly 3,000 people killed in the attacks — both those who want a full trial, no matter how long it takes, and those who have accepted the settlement as the only sure path to a conviction that cannot be appealed.
At Guantánamo Bay, relatives who were brought by prosecutors for a weeklong visit to watch the proceedings reacted emotionally.
“It was supposed to be a time of healing for us,” said Claire Gates, whose uncle, Fire Lt. Peter L. Freund, was killed at the World Trade Center. “We will board that plane with a sense of deep pain. There is no end to it.”
Justice Department lawyers had urged the three-judge panel to stop Friday’s hearing because it “would likely make it impossible to unwind the pleas later.”
Defense lawyers quoted a letter from the chief war crimes prosecutor to the Sept. 11 families this summer saying that the settlement was the “best path to finality and justice in this case.”
The panel set an expedited schedule on the question of whether Mr. Austin effectively canceled the pleas. It gave the Justice Department until Jan. 22, two days after President-elect Donald J. Trump takes office, to make its final filing, and said oral arguments would follow.
Thomas Resta, who lost his brother John and sister-in-law Sylvia in the attacks, said he was let down by the Biden administration. “The government had the chance to do the right thing by the families and decided not to,” he said. He said he was concerned about the Trump White House exerting undue influence to disrupt the case further.
The incoming Trump administration has not publicly indicated how it might handle the case.
Col. Matthew N. McCall, the military judge, had prepared a 103-page list of questions to be posed to Mr. Mohammed at the hearing Friday to determine whether he fully understood and voluntarily signed a plea agreement and accompanying confession. It would have been the first step in a trial to determine Mr. Mohammed’s sentence.
In court on Wednesday, Clayton G. Trivett Jr., the lead prosecutor, who had negotiated the plea, described plans for a sentencing trial that he said would start late this year and was likely extend into 2026. It would include a monthslong presentation to the panel and the public “to establish a historical record of the accuseds’ involvement in what happened on Sept. 11,” he said, as well as potentially hundreds of victim impact statements by survivors or relatives of those killed.
Pentagon prosecutors brought fathers, brothers, sisters, a husband and an uncle of those killed on Sept. 11 to watch the proceedings. The Pentagon said they were chosen by lottery, but all appeared to support the resolution of the case.
Word of the freeze came as five reporters who were on base to cover the proceedings were meeting with them. “By doing this, the Biden administration failed the families of 9/11,” said Stephan Gerhardt, whose brother Ralph was killed in the attack on the World Trade Center. “We cannot pin our hopes on the next administration to resolve this.”
The Pentagon had established five viewing sites for families to watch the plea on Friday at Fort Devens, Mass.; Fort Meade, Md.; Fort Hamilton, N.Y.; a Marine reserve station at West Palm Beach, Fla.; and an Army reserve base in Farmingdale, N.Y.
