The CIA psychologist who helped design a torture program to interrogate the accused mastermind behind the Sept. 11, 2001, terror attacks says the Guantanamo Bay military commission in Cuba is "delaying justice" for victims.

Khalid Sheikh Mohammed, the accused planner of the terror attacks, and four other Gitmo detainees appeared together in court Tuesday for the first time in 500 days for pretrial hearings after delays brought on by the coronavirus pandemic. The hearings, which resumed Wednesday, are the latest attempt to advance a case that has been bogged down for years amid legal challenges

"He's saying he's not guilty because he was at war with us," Dr. James Mitchell told Fox News of Mohammed. "He has not denied doing the things that he did. He just says he was justified because it's God's work for them to do it."

** FILE ** Khalid Shaikh Mohammed, the alleged Sept. 11 mastermind, is seen shortly after his capture during a raid in Pakistan Saturday March 1, 2003 in this photo obtained by the Associated Press. American authorities investigating the killing of Wall Street Journal reporter Daniel Pearl in Pakistan now believe that he was slain by the hand of Mohammed. The U.S. acknowledgment of Mohammeds suspected role was first reported in the Wall Street Journal Tuesday, Oct. 21, 2003. (AP Photo)

Khalid Shaikh Mohammed, the alleged Sept. 11 mastermind, is seen shortly after his capture during a raid in Pakistan Saturday March 1, 2003 in this photo obtained by the Associated Press. (AP Photo)

Mitchell thinks "the people involved in the case want to provide him with a fair trial and are going out of their way – bending over backward – to provide him with not just a fair trial, but the appearance of a fair trial, and so much so that I think in some ways they're delaying justice," Mitchell said.

Mohammed and his four other co-defendants are charged with several crimes, including terrorism, hijacking and 2,976 counts of murder for their alleged roles in planning and providing logistical support to the Sept. 11 plot. 

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The quintet have been held at Guantanamo Bay since September 2006 after several years in clandestine CIA detention facilities following their capture.

Air Force Lt. Col. Matthew McCall, the latest and seventh different judge assigned to the case, said on Wednesday in the courtroom that the death penalty is a "valid option" for the five 9/11 prisoners and that he "can be a fair judge."

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Mitchell also criticized the Biden administration's handling of the U.S. military's withdrawal from Afghanistan before Aug. 31 as the nation approaches 20 years since 9/11 and said the Taliban will likely place blame for future attacks on other terror groups.

"In terms of responding to any attack that comes out of the Taliban, they're going to probably try to distance themselves from that," he said of the terror group. "You may remember that the Taliban told [President] Biden that 'we won't attack your people,' and then [they] let ISIS attack and kill those 13 Marines."

US psychologist James Mitchell (L) speaks with an interviewer at the American Enterprise Institute in Washington, D.C., on December 6, 2106. (Photo credit should read THOMAS WATKINS/AFP via Getty Images)

He continued: "The suggestion that we can treat the people that want to impose sharia law on the world as if they were an ordinary government is, I think, naive."

Mitchell did not get into specifics about the Mohammed case due to a nondisclosure agreement but did reflect on his efforts to interrogate the accused terrorist in 2003, which included torture methods ranging from slapping to waterboarding and sleep deprivation. He recalled one moment when Mohammed predicted during an interrogation the "lone wolf" terror attacks that would occur in the U.S. post-9/11.

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"He said it would be nice if we could … continue with a series of attacks, but that's not how it's going to happen. We're going to immigrate into your country, you are going to support us with your welfare, you're going to protect us with your civil rights, and then, when the time is right, we are going to rise up and attack you. And we said soon, he said … America will expose her neck for slaughter," Mitchell said.

The torture tactics CIA operatives used against Mohammed, which were either approved by the Justice Department or CIA at the time, have come under scrutiny by Congress and other critics. 

The medical psychologist's program has been criticized by two congressional committees and the CIA's covert internal watchdog, but Mitchell did not seem phased by those who disagreed with his methods.

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"The five directors of the CIA said it was effective," he said of the torture program. "I mean, who are you going to believe? Some angry FBI guy who didn't get around to soak up the glory for himself or … these CIA directors? And I think the Senate Select Committee minority report – not the majority, but the minority report – did a really good job of rebutting this notion that it wasn't effective."

He added that critics "can say what they want to say and maybe that helps them sell books and maybe that helps them, you know, advance their personal goals, but it just isn't true."

Fox News' Lucas Tomlinson and Vandana Rambaran contributed to this report, as well as the Associated Press.