A former Air Force psychologist who waterboarded terrorist Khalid Sheikh Mohammed poured cold water on claims Mohammed suffered a brain injury from being subjected to torture while in U.S. custody.

Dr. James Mitchell appeared on Fox News on Wednesday night and was asked about Mohammed's lawyers arguing their client has brain damage.

"Nothing his attorneys do surprises me," Mitchell said. "Basically, it's obvious that he's guilty. Everybody knows that he's guilty, and I know it's flippant to say that, but it's true.

"And now they're just looking for some way to save his life. We have to step back and ask ourselves, what is their motivation?

"Well, their motivation obviously is to prep the battlefield, the legal battlefield, to make him appear a victim, to make it appear like he's more human, and to set the grounds for some kind of plea agreement that doesn't involve the death penalty."

Mitchell participated in waterboarding and walling seasons involving Mohammed. Walling involves putting a special collar around a detainee and slamming him against a wall. The collar is designed to prevent the person's head from striking the wall.

Mitchell was adamant Mohammed's torture sessions were conducted under the rules.

"We did not slam his head against the wall, and that's the thing that gets repeatedly said," Mitchell said. "In fact, he was walled no harder than we wall our own soldiers. And there were, specifically, things that were put in place by the CIA to ensure that the kind of head damage that he's alleging couldn't have occurred."

Those controls included the collar and numerous checks by a doctor, Mitchell noted.

Mohammed's lawyers argued in court documents in March that scans of his brain taken in January showed "evidence of head injuries consistent with the physical trauma suffered by Mr. Mohammed and documented in the SSCI Executive Summary."

The SSCI Executive Summary was the 2014 Intelligence Committee report on the CIA's post-9/11 torture program.