After a long COVID-19 halt, the pretrial wrangling in the case of accused 9/11 mastermind Khalid Sheikh Mohammed and four other defendants resumed Tuesday, two decades after the attacks and nine years after war crimes accusations were filed.

Mohammed, dubbed "KSM" and identified in the 9/11 Commission Report as "the principal architect of the 9/11 attacks," and some of his co-defendants were smiling and chatting with each other and their lawyers, with KSM waiving to the gallery briefly.

KSM was a close ally of Osama bin Laden, and when in U.S. custody, he was regularly waterboarded. His nephew, Ammar Baluchi, is accused of sending money transfers to 9/11 hijackers within the U.S., as well as claimed hijacking trainer Walid bin Attash, 9/11 facilitator Ramzi bin Shibh, and al Qaeda money man Mustafa Hawsawi.

Since the detainees were arraigned at Guantanamo Bay in 2012 during the Obama administration, the case has faced a number of difficulties. The ongoing COVID-19 pandemic and personnel changes prompted the most recent 18-month hiatus.

Throughout the two and a half hours they were in court, the detainees spoke with each other at the edges of tables set up along the left side of the courtroom, both during the hearing and during two courtroom recesses.

In the order of detainees, Mohammed sat closest to Judge Col. Matthew N. McCall, with his arm thrown across the back of his chair, conversing with Bin 'Attash, who sat behind him in the order of detainees.

Mohammed stepped out of the courtroom, escorted by guards, during the first recess. On his way out, he waved to two reporters in the gallery.

Baluchi's lawyer, James Connell, said his client was conversing with the other detainees and his legal team because he was relieved to be out of lockdown.

When the trial begins, KSM will be charged with 2,976 counts of murder and related charges in connection with the collapse of the Twin Towers, the attack on the Pentagon, and the downing of an airliner in a field in Shanksville, Pennsylvania on Sept. 11, 2001.

He and his co-defendants will face the death penalty. There is no set date for the trial.