Khalid Sheikh Mohammed, the accused mastermind of the 9/11 terror attacks, seemed to be in a jovial mood Tuesday as his trial by a military commission resumed after months of delays at Guantanamo Bay, Cuba.

Mohammed, also known as KSM, joined four co-defendants — Ammar al-Baluchi, Walid bin Attash, Ramzi bin al-Shibh and Mustafa Ahmad al-Hawasawi — for the first time since their pre-trial hearings were suspended in February 2020. 

Fox News reported that the five were seen smiling as they observed the proceedings — with KSM waving to reporters as he exited the courtroom during a break. He and his co-defendants only spoke publicly to say “yes” when the military judge asked if they were ready to proceed. 

When the trial begins, KSM will face 2,976 counts of murder and related charges in connection with the toppling of the Twin Towers, the attack on the Pentagon and the downing of an airliner in a field in Shanksville, Pa. on Sept. 11, 2001. He and his co-defendants will face the death penalty. No date for the trial has been set. 

The delay in proceedings has been caused by a myriad of issues — including the coronavirus pandemic, the retirement or transfer of judges, and questions over the admissibility of evidence obtained by the Central Intelligence Agency (CIA) through the use of torture. 

Tuesday’s hearing was presided over by Air Force Lt. Col. Matthew McCall, who is the fourth military judge on the case. Much of the hearing revolved around defense lawyers questioning McCall’s qualifications and links to previous lawyers involved in the case, the Guardian reported. 

This week’s hearings are set to last until Sept. 17, and are scheduled to be followed by another set of hearings from Nov. 1-19, according to ABC News. Proceedings can be halted at any time for national security reasons. The hearings are now in their ninth year. 

Mohammed was captured in March 2003 in a house in Rawalpindi, Pakistan, along with al-Hawsawi and several others.

While KSM admitted to committing multiple horrors — including personally decapitating Wall Street Journal reporter Daniel Pearl on video; organizing the 1993 bombing of the World Trade Center; masterminding the October 2002 bombing of a nightclub in Bali, Indonesia; and planning “shoe bomber” Richard Reid’s failed attempt to blow up a passenger plane over the Atlantic Ocean in December 2001 as well as“the 9/11 operation” — he made the admissions at a secret overseas CIA “black site” where he was waterboarded 183 times and subjected to other so-called “enhanced interrogation” techniques. 

As a result, none of that evidence obtained in those interviews has been able to be used against him.

The Department of Defense came under fire earlier this year when KSM and other detainees at Guantanamo Bay were administered the coronavirus vaccine before much of the American public. 

In January, a spokesman for the Department of Defense confirmed that officials had signed an order which will see COVID-19 vaccinations “offered to all detainees and prisoners.”

As of July, 39 prisoners remain at Guantanamo. 

In 2019, Richard Miniter, author of the 2011 book “Mastermind: The Many Faces of the 9/11 Architect, Khalid Shaikh Mohammed,” said it was unlikely KSM would get the death penalty, noting that the military hasn’t executed anyone since 1961.