Col. Matthew N. McCall, the judge, disqualified Ramzi bin al-Shibh, 51, from what had been a five-defendant conspiracy case in an 11-page ruling.

For years, Mr. bin al-Shibh has said he was tormented by invisible forces that caused his bed and cell to vibrate and that stung his genitals, depriving him of sleep. He has disrupted court proceedings and the peace at the prison for “high-value detainees” who were subjected to “enhanced interrogation” such as waterboarding, beatings and sleep deprivation in C.I.A. custody.