The self-described mastermind of the 9/11 attacks, Khalid Sheikh Mohammed, known by his initials KSM, is accepting a plea deal for life in prison. KSM was captured in Pakistan in 2003, before being held in the Guantanamo Bay Military Prison. In 2011, along with four other co-defendants, he was arraigned in a military commission, but since then, for the past 13 years, the trial has been tied up in pretrial hearings. Yesterday, we finally learned that there will be no trial. KSM and three defendants accepted a plea and will be spared the death penalty.

GBH’s All Things Considered host Arun Rath has been covering the trial on and off for the last 13 years, and joined GBH’s Morning Edition co-host Jeremy Siegel to talk about his experiences. This transcript has been lightly edited for clarity.

Jeremy Siegel: Tell us about this mastermind, Khalid Sheikh Mohammed. What was his involvement in 9/11 and how did he end up in the prison in Guantanamo?

Arun Rath: He was really the mastermind, self-described mastermind. He’s proud of this fact. He was the architect, the ideas guy. Osama bin Laden gave the order, but Khalid Sheikh Mohammed came up with a whole plan to hijack planes and fly them into buildings, you know, down to using box cutters to kill the crew. It was it was entirely his plan.

Siegel: And how did he end up being taken to Guantanamo?

Rath: Well, he was captured in Pakistan in 2003, and then he was basically not seen for a couple of years and turned up in Guantanamo a couple of years later. We now know that after his capture, he was kept in CIA black sites, one of them in Afghanistan. And he was tortured, waterboarded. And after showing up in Guantanamo — this was back when [President] George W. Bush created military commissions to try war on terror detainees — the first Khalid Sheikh Mohammed trial in the military commission got derailed.

Then, President Obama was elected, and President Obama tried to move the trial to a civilian court, wanted to try this in New York City. That also got derailed for various reasons. Then the military Commission 2.0, I guess you would call it, started in 2011. And one of the things I want to add to the narrative about Khalid Sheikh Mohammed, to keep in mind, is that, not only was he responsible for the 9/11 attacks, but, afterwards, before he was captured, he [said he] murdered Wall Street Journal reporter Daniel Pearl in Pakistan. So that’s not on his list of charges, but that’s something that he also claimed responsibility for.

Siegel: Arun, you covered the court proceedings surrounding KSM. What was it like seeing him in the flesh in court?

Rath: It’s really intense, Jeremy. I mean, I was in New York on 9/11, so I’ve got some strong feelings about the guy. ... In the courtroom, you’re in the gallery, you’re behind double-paned glass — so there’s a bit of a remove — but still getting to see him in the flesh is really intense. He grown like a long sort of jihadi beard and tries to make himself look pious, even though he’s not a very pious individual. And one of the most intense moments I can recall was ... one of the reporters was actually Daniel Pearl’s best friend. And I was with her and standing in the gallery, like, watching this man who had murdered him. Kind of unforgettable.

Siegel: Not many people have been to Guantanamo Bay. What is it like being there as a journalist? And what’s the court scene itself like?

Rath: There’s no kidding around how utterly bizarre it is. I’ve done other military trials in the military justice system. And so the courtroom is — the military commission is very much like a military-style court: The military judge, prosecutors and so on, but it’s planted in the middle of Guantanamo Bay, Cuba, in this U.S. military base. And the courtroom itself is really strange because of security concerns. Even when you’re in the gallery, you’re hearing everything on a 30-second delay, and that’s set up so that a court security officer can cut the audio if anybody says anything involving classified material. Now, when the trial started out, that was because if anyone mentioned torture, or anything that had happened in the CIA custody of Khalid Sheikh Mohammed, they would have to cut it out because all of that was classified.

One strange thing that happened in the course of these 13 years, a couple of years in, the Senate report on CIA torture came out. So all of a sudden that was declassified. So all of a sudden, going back to court, all of this stuff that lawyers couldn’t talk about was being talked about widely.

Siegel: Let’s talk a little more about the court case itself. You were first there for his arraignment in 2011. It is now 2024, and we have this deal. What has been going on that entire time legally?

Rath: Well, the pretrial process is a normal process where you’re setting up normal things like what can be entered into evidence, who can the witnesses be? But the real thing that got all of this tied up, Jeremy, is because this man, Khalid Sheikh Mohammed, was tortured in CIA custody. So this is what a lot of the arguments have been about. And that kind of gets to the end of what happened with this. The reason that his lawyers want to talk about this is because the fact that he was tortured provides mitigation. That gives them the moral argument that therefore the government cannot execute them. They’ve lost the moral ground to because of abusing them with the torture. And that’s essentially what’s happened with this case, with the settlement that they’ve agreed to with the lawyer. They’ve agreed to life sentences, without the chance of execution, because of the abuse that they went through. So that’s what happens here. The 9/11 victims’ family members won’t get a trial there. He won’t be executed. But he will be in prison indefinitely.

Siegel: In the 20 seconds I have before I let you go, Arun, how are you making sense of this decision and what it means for victims?

Rath: It’s hard because, you know, I’ve talked to a lot of the victims. They feel all over the place. Some desperately want to see him executed. Others just want it to be over, the way it is. So I think a lot of people feel good for a certain amount of closure with this now, but it’s also, it’s still kind of an open wound, Jeremy. I don’t know if there will ever be closure.