Dr. Mitchell and Dr. Jessen started off as contract consultants to the C.I.A. and went on to waterboard three other prisoners now at Guantánamo in addition to Mr. Mohammed, starting with a Palestinian man called Abu Zubaydah. By 2005, they set up a business, Mitchell Jessen and Associates, that grew to provide all of the contract guards at the black sites and 80 percent of the agency’s interrogators. The United States government paid the business $81 million for their services.
Mr. Zubaydah, who has never been charged or convicted of a crime, is an indefinite detainee at Guantánamo in the same prison as Mr. Mohammad and the others. He recently drew sketches of the application of the interrogation techniques in clinical detail.
It is unclear how much of the testimony the public or the defendants will get to see.
The C.I.A., through the prosecution, still controls the classified information surrounding the black sites — including their locations and the identities of most people who worked there, as well as deciding who can testify and what they can divulge.
The Sept. 11 case prosecutors have periodically invoked a national security privilege to prevent the public and the defendants from hearing some information. And in closed national security sessions, they have invoked the privilege to prevent the judge and the defense lawyers from hearing some information.
The judge, Col. W. Shane Cohen of the Air Force, ultimately has to decide whether the government has shielded so much information it would prevent the defendants from getting a fair trial and, if so, how to provide balance before the trial’s start, which is scheduled for Jan. 22, 2021, with jury selection. Remedies could include dropping the death penalty as a possibility or dismissing the charges.
Trial lawyers in the case have been preparing for the high-stakes hearing for months, with defense teams reviewing Dr. Mitchell’s media appearances and his book, “Enhanced Interrogation,” and studying the depositions both men gave in 2017 in the A.C.L.U. lawsuit.
“They were among the founding fathers of the torture program,” said Walter B. Ruiz, the lawyer for Mustafa al-Hawsawi, one of the defendants.