Lost Witnesses, Faded Memories Impede Progress in Sept. 11 Case

Four years ago, in dramatic testimony, a U.S. psychologist described in open court how he had threatened to slit the throat of a young son of Khalid Shaikh Mohammed, the accused mastermind of the Sept. 11 attacks, if another Qaeda attack claimed the life of an American child.

On Wednesday, Dr. James E. Mitchell told a stunned courtroom that episode had not happened. “I didn’t say anything about killing his son,” said Dr. Mitchell, a retired Air Force psychologist who in 2003 waterboarded Mr. Mohammed 183 times for the C.I.A. “He didn’t have sons until later.”

Dr. Mitchell later acknowledged he had forgotten his threat. But the episode underscores a new challenge for the military court in the case against four prisoners who are accused of conspiring in the attacks that killed nearly 3,000 people on Sept. 11, 2001: the fading memories and unavailability of witnesses whose testimony is central to getting the death-penalty case to trial.

Testimony and other evidence often deteriorate over time, which is one reason that criminal defendants and their victims are entitled to a speedy trial.

This month, two retired Army officers were too ill to travel to Washington to testify about the defendants’ health and prison conditions at Guantánamo in early 2007. It was a critical period in the case, when prosecutors say the defendants voluntarily confessed to their crimes. Defense lawyers argue the confessions were contaminated by torture and secret collaboration between the F.B.I. and the C.I.A.

One witness was the defendants’ first psychiatrist at Guantánamo. The other was their first prison commander. A third key witness from that period, the prisoners’ first treating physician at Guantánamo, died in 2018 before his testimony could be