WASHINGTON (CNN) -- Three of five Guantanamo Bay detainees who said they wanted to confess to charges relating to the September 11 terrorist attacks rescinded the offer after a judge required two to undergo competency hearings, according to a military spokesman.
A sketch shows Walid bin Attash, left, and Khalid Sheikh Mohammed in court at Guantanamo Bay in June.
Khalid Sheikh Mohammed -- the confessed architect of the attacks who was captured two years later in Pakistan -- and four other alleged co-conspirators asked a military judge Monday whether they could withdraw all pending motions and plead guilty to conspiracy and murder charges, Maj. Gail Crawford said in an e-mail.
The military judge initially accepted the requests from Mohammed, Ali Abdul Aziz Ali and Walid bin Attash but ruled that competency hearings are first needed for Mustafa al-Hawsawi and Ramzi Bin al-Shibh, because "questions exist as to their competency to stand trial," Crawford said.
After the judge made that ruling, Mohammed, Ali and Attash rescinded their offer to plead guilty.
It has not been determined whether the defendants, formally charged in June, will face a potential death sentence.
The defendants announced their decision in front of relatives of victims in the al Qaeda-orchestrated attacks, said Jennifer Daskal, senior counterterrorism counsel for Human Rights Watch. She attended Monday's hearing.
The five are among the defendants in a heavily scrutinized proceeding that experts say may serve as a bellwether for future hearings involving foreign fighters.
The commissions have been delayed for years by legal challenges, and the U.S. Supreme Court ruled an earlier version of them unconstitutional in 2006.
"What should have been a major victory in holding the 9/11 defendants accountable for terrible crimes has been tainted by torture and an unfair military commissions process," Daskal said Monday.
"This is the government's last hurrah," she said, referring to the final weeks of the Bush administration's second term, which ends January 20.
But Hamilton Peterson, whose father and stepmother died aboard the hijacked jet that crashed into a Pennsylvania field, said the defendants received due process -- and "they were mocking it."
"I think the fact that we as a country are taking the high road, and the fact that all of you are here -- including international press, including Al-Jazeera -- that it is unequivocal how fair we are and that this is the only way to move forward," he said.
Denis McDonough, a senior adviser to President-elect Barack Obama, said that no decisions have been made about what to do with the 255 inmates at the detention facility at the U.S. naval base at Guantanamo Bay, Cuba, and that "there is no process in place to make that decision until his [Obama's] national security and legal teams are assembled."
But officials close to the Obama team said that the incoming administration is pondering putting some of the Guantanamo Bay inmates on trial in existing federal courts, setting up a special national security court to deal with cases involving the most sensitive intelligence information, and releasing other inmates.
The detention facility was created on the grounds of the naval base after the September 11 attacks that killed nearly 3,000 people in New York, Washington and Pennsylvania and was intended to house foreign fighters captured on the battlefield.
Some conservatives have expressed reservations about the idea of bringing suspected terrorists whom the government calls dangerous to the U.S. mainland.
"There's really no place in the United States that can replicate the sort of operational security features that Guantanamo has," said David Rivkin, a former Justice Department official.
And Maureen Santora, who attended Monday's proceedings, said she was glad Guantanamo was there.
"I certainly think that this detention facility has provided a respite for the rest of America against people that are trying to harm us, and I am very, very grateful that it is not on the mainland," said Santora, whose son Christopher was a firefighter killed at at the World Trade Center in New York.
In 2006, President Bush said he would like to close the prison but announced that it needed to remain open to house "cold-blooded killers."
The Pentagon's chief prosecutor resigned in protest in 2007 after declaring that the military commissions had become "deeply politicized."
Critics say the camp has damaged the reputation of the United States overseas, with a U.N. report declaring that interrogation techniques used on prisoners "amounted to torture."
The White House has consistently denied that the United States practices torture, but CIA officials have admitted to using at least one technique -- "waterboarding" -- that has been considered a war crime in the past.
Several detainees, including Mohammed, were moved to Guantanamo Bay in September 2006 after being held in secret CIA prisons around the world.
CNN Senior Pentagon Correspondent Jamie McIntyre contributed to this report.