The admissions made by the mastermind of the Sept. 11 attacks illuminated and transformed the cases against him and the 13 other Qaida leaders transferred last year from CIA prisons to the U.S. Navy base at Guantanamo Bay, Cuba.
In acknowledging last Saturday his role in more than 30 terrorist attacks and plots, Khalid Shaikh Mohammed certainly simplified the case against himself and may have effectively signed his own death warrant when he eventually faces a military trial.
But those same statements, released on Wednesday by the Defense Department, may complicate the prosecution of his former colleagues.
Speaking to a military tribunal that considers just the narrow question of whether Guantanamo detainees were properly designated as enemy combatants, Mohammed was so expansive in his acceptance of responsibility that other defendants might be able to use his statements in their own defense.
In a transcript of the hearing, Mohammed also disavowed information he had told CIA interrogators about his accomplices, again potentially helping the other defendants.
A revised version of the transcript released Thursday added another chilling confession. Mohammed said he decapitated Daniel Pearl, a reporter for The Wall Street Journal, in Pakistan in 2002. The military said it had held back the passage about Pearl while it notified his family.
That confession could figure in the case of Ahmed Omar Sheikh, who is appealing his death sentence in Pakistan for his role in Pearl's abduction and murder. Mohammed and the other Qaida leaders will eventually face charges before military commissions that they are guilty of war crimes, many of which carry death sentences.
Unlike the recent proceedings, before Combatant Status Review Tribunals, those trials will largely resemble ones before civilian criminal courts. Officials have said that they intend to charge the men this year and that those trials could start early next year.
The trials of three less-significant detainees, none of them among the 14 leaders, are expected to begin soon.
It is not clear whether Mohammad was really involved in as many terrorism plots as he said or whether he was simply indulging in a penchant for drama and self-aggrandizement. Nonetheless, his confession could have a significant effect on the round of tribunals. Several lawyers said his statement could be used against him in other settings.
"This statement is admissible and substantially hampers the ability of the defense to argue that he is not guilty," said David B. Rivkin, an official in the administrations of Ronald Reagan and the elder George Bush. "The other side may argue that the poor dear was so stressed out by his earlier treatment that it had a lingering effect. That dog ain't going to hunt."
John Sifton, a senior researcher at Human Rights Watch, said he questioned whether the statement read for Mohammed by his representative authentically reflected his views.
"The grammar of it alone, when juxtaposed with his version of English, suggests it was prepared for him," Sifton said. "It looked to me like it was printed out of whitehouse.gov."