A military judge has barred prosecutors from using a 2007 confession by accused 9/11 mastermind Khalid Sheikh Mohammed, ruling that the statements were not voluntary and delivering another major complication to a prosecution that has already dragged on for more than two decades.

Lt. Col. Michael Schrama concluded that statements Mohammed gave investigators in 2007 could not be admitted against him, according to a report by the New York Post. The ruling was not initially released publicly, but sources familiar with the decision said the judge had excluded Mohammed’s confessions from the case.

Mohammed, who has been held at Guantánamo Bay for more than two decades, is accused of serving as the principal architect of the Sept. 11, 2001, terrorist attacks, in which nearly 3,000 people were killed.

The decision creates yet another potential obstacle as the military commission attempts to finally bring Mohammed and his alleged co-conspirators to trial after years of legal disputes, procedural battles and repeated delays.

The development came during the same week that Schrama established June 2028 as the trial date for Mohammed and three co-defendants: Walid Muhammad Salih Mubarak bin ‘Atash, Mustafa Ahmed Adam al Hawsawi and Ali Abdul Aziz Ali. The announcement came shortly before the 25th anniversary of the Sept. 11 attacks.

Prosecutors had sought to begin proceedings much sooner, asking for a January 2027 trial. Schrama rejected that timetable, finding that it would not provide sufficient time for the “resolution of pretrial evidentiary and compliance motions.”

Military prosecutors were contacted by Fox News Digital regarding Friday’s decision. The organization 9/11 Families United declined to offer Fox News Digital a comment on the ruling.

The exclusion of Mohammed’s confession is the latest development in a case that has repeatedly stalled amid complicated legal fights, including disputes involving evidence and unsuccessful attempts to resolve the prosecution through plea agreements.

A major effort to settle the case appeared to be taking shape in 2024, when Mohammed, Walid bin Attash and Mustafa al-Hawsawi agreed to acknowledge their involvement in the Sept. 11 attacks. Under that arrangement, the three would receive life sentences and be spared the death penalty.

All three defendants remain in U.S. military custody at Guantánamo Bay, Cuba.

The proposed agreements prompted intense criticism from numerous relatives of those murdered on Sept. 11, many of whom objected to an arrangement that would remove the possibility of capital punishment.

The Biden administration subsequently withdrew the deal, a decision that triggered additional litigation and further complicated efforts to bring the extraordinary long-running case to a conclusion.

Beyond taking the death penalty off the table, the proposed agreement would have required the defendants to respond to questions from victims’ families seeking answers about the planning and execution of the attacks.

With Mohammed’s 2007 statements now excluded and the trial scheduled for June 2028, the prosecution of the men accused of orchestrating the deadliest terrorist attack on American soil is poised to continue well beyond the attack’s 25th anniversary.