A federal appeals court in Washington, DC has thrown out a proposed plea deal for Khalid Sheikh Mohammed, the alleged mastermind of the 9/11 attacks, effectively halting what was expected to be a major development in one of the most prolonged military prosecutions in US history. In a 2-1 decision, the court ruled that then-Defence Secretary Lloyd Austin had acted within his authority when he blocked the agreement last year, a move that prosecutors said was necessary to preserve public confidence in the military tribunal process.The deal, which had taken two years to negotiate and had been approved by military prosecutors and senior Pentagon officials, would have seen Mohammed and two co-defendants plead guilty in exchange for life imprisonment without parole. The agreement also included a commitment from the defendants to answer victims’ families’ lingering questions. But Austin intervened, arguing that such a significant decision—removing the death penalty from consideration—should be made only by the defence secretary.“Having properly assumed the convening authority, the Secretary determined that the ‘families and the American public deserve the opportunity to see military commission trials carried out.’ The Secretary acted within the bounds of his legal authority, and we decline to second-guess his judgment,” wrote Judges Patricia Millett and Neomi Rao.In a strong dissent, Judge Robert Wilkins wrote: “The government has not come within a country mile of proving clearly and indisputably that the Military Judge erred.”Mohammed, now 59, appeared in court earlier this week dressed in traditional clothing, his beard dyed bright orange. Asked by the judge if he was pleading guilty to all charges “without exceptions or substitutions,” his lawyer replied, “Yes, we can, Your Honour.” But before the plea could be officially entered, the court was informed that the deal had been paused.Many of the victims’ relatives had flown to Guantanamo Bay to witness the proceedings, only to learn at the last minute that the pleas would not proceed. “It’s like a perpetual limbo… It’s like constant whiplash,” said Elizabeth Miller, whose firefighter father died in the attacks.With the case now back in limbo, any resolution appears unlikely until after the next US administration takes office. Guantanamo Bay, once home to nearly 800 detainees, now holds just 15 men, most of whom have not been convicted.