With victims' family members in attendance, the alleged mastermind of the Sept. 11, 2001, attacks asked to postpone an earlier offer to plead guilty to murder charges and voiced concern that he might not be sentenced to death if he and his co-defendants plead guilty.
"Are you saying if we plead guilty we will not be permitted under the law to be sentenced to death?" he asked Army Col. Steve Henley, the judge presiding over the pretrial hearing in the war-crimes case at Guantanamo Bay, Cuba.
Khalid Sheikh Mohammed, also known as KSM, is facing charges of murdering 2,973 people. He has admitted to developing the plot to fly airplanes into buildings and allegedly insisted the planes hit buildings, even when Osama bin Laden purportedly said hijacking them and crashing them in the ground would be enough.
KSM, who said during his June arraignment that he wished to be "martyred," also expressed dismay that "two of his brothers" would not be able to join in entering the plea, as they have competency issues pending before the court.
He and four others are facing charges related to the attacks and could be sentenced to death if found guilty.
Earlier Monday, Henley read aloud a letter in which the five men said they "request an immediate hearing session to announce our confessions." In court, KSM added, "We want to enter our plea… we do not want to waste time."
Henley and the attorneys are now trying to determine whether the men can legally plead guilty and avoid trial.
The judge asked each man whether he would enter a plea and three said they agreed with the letter. KSM had told the court that he and his four alleged co-conspirators met the day after Barack Obama was elected president to discuss the motion.
Obama has vowed to close Guantanamo, but has not laid out plans addressing where the alleged terrorists will go or what kind of trials they will face.
Immediately after the hearing kicked off Monday morning, KSM questioned the court about the slow response to the written requests he'd filed, noting one had taken 50 days. He then dismissed his military counsel, which was meant to offer legal guidance as he is representing himself, on the grounds that counsel members had served in Iraq and had allegedly killed Muslims. He also stated in court that he doesn't trust the judge, President Bush or the CIA, which he says tortured him.
CIA director Michael Hayden acknowledged earlier this year that CIA agents or contractors waterboarded KSM. The controversial interrogation technique simulates drowning.
As for Monday's hearing, the head of the American Civil Liberties Union offered up some harsh criticism.
"It was a complete circus today," said ACLU executive director Anthony Romero. "The rules are unclear. The defendants didn't understand it. The judge himself is unclear about what rules to apply. It just shows that the military commissions are fundamentally flawed. They can't be fixed. It won't get better. They just need to be shut down."
KSM appeared much as he did at his arraignment in June, wearing a white robe and white head scarf and a long, flowing gray beard. The summer court appearance was the first time he had been seen in public since his 2003 capture.
A small group of victims' family members and their guests are at Guantanamo Bay to witness the trial. In the courtroom, they are shielded from the media by a glass wall, but have a full view of KSM and the others on trial.
Maureen Santora held a photograph of her son, Christopher, a New York City firefighter who responded to the World Trade Center, because she said she wanted him to be a part of the proceedings. When Mohammed offered to confess, she said she wanted to jump up and down with joy.
Another mother shared her recollection of the morning of the attacks with ABC News as she prepared to make the trip to Guantanamo.
Seven years ago on the morning of Sept. 11, the phone rang for Alice Hoagland.
"Mom, this is Mark Bingham," said the young man, giving his mother his full name. "I'm on a flight from Newark to San Francisco. There are three guys who've taken over the plane, and they say they have a bomb."
"You believe me, don't you, Mom?"
Bingham, a 31-year-old entrepreneur with a zest for rugby and adventure, was on United flight 93, headed home to a friend's wedding in California.
The phone went quiet. And then Hoagland said what would be among her last words to her only son: "Yes, Mark, I believe you."
On Sunday, Hoagland arrived at Guantanamo Bay to finally see the man who had orchestrated the attacks. She is among a group of victims and families chosen by a lottery to watch his military commission hearings.
"You'd have to be a very bloodthirsty and inhuman person to hatch such a plot," Hoagland told ABC News. "That's one reason why I'm glad I'm going to sit in the same room with Khalid Sheikh Mohammed and sort of take measure of that man, because he claims responsibility. He takes credit, if you will, for hatching that ugly plot."
The deadly impact of that plot shattered Hoagland's life.
"I still wake up nights startled by the fact that my only child is dead," she said. "They've taken the most precious thing out of my life. I'll never be the same."
Hoagland has made another life, as an advocate for the victims' families and for reform. In a way, she has moved on.
But she also remains very much back in that day, when she got that phone call from Bingham. She and other victims' family members have listened to the cockpit tapes, and she describes them in graphic detail -- the shouting and thunderous noises as Bingham and other passengers stormed the cockpit, the wind screaming over the plane's wings as it hurled to the ground.
And when she talks about that day, she relives it.
After Bingham's call to her the morning of Sept. 11 was cut off, Hoagland, desperate for information, began frantically calling "everybody we could think of." The FBI, United Airlines, the police.
She turned on the television, and she saw the horrific scene of the World Trade Center in flames. And then she saw the second plane hit.
"It was… it was the most horrible…," she said, her voice trailing off. "I thought, 'Is that Mark's plane?'" It turned out that it wasn't.
"Then we heard about the Pentagon being hit. Was that Mark's plane? And then they started announcing what flight numbers they were. United Airlines 175 into the South Tower. American Airlines flight 11 into the North Tower. American flight 77 into the Pentagon."
And then her sister-in-law frantically called her to the television: "Guys, they just mentioned Flight 93."
This is what Hoagland saw on the television screen: "They showed a panorama of the scene there outside of Shanksville, Pa., with hemlock trees afire and a huge, gaping hole covered over with some debris and emergency crews standing around, already."
"Seeing that," she said, "I knew that, of course, there were no survivors."
On that day, she had never heard of KSM, the self-confessed mastermind of the plot that killed her son and 2,972 others. Monday, she was in the same courtroom, watching.
On the flight down to Guantanamo Sunday, she told ABC News that she feels "dread" at seeing him.
But she also said she wishes KSM and the other terrorists could see more of the victims' families, "and to look into the faces of all the thousands of people whose lives they changed so bitterly that day."
She is only one.
The Associated Press contributed to this report.