Khalid Sheik Mohammed, called KSM, is accused of masterminding the Sept. 11 attacks by proposing the idea to Osama bin Laden in 1996, overseeing the operation, and training the hijackers in Afghanistan and Pakistan. The CIA subjected him to an interrogation technique called waterboarding before his 2006 transfer to Guantánamo Bay. In March 2007, according to a military transcript, he boasted: ''I was responsible for the 9/11 operation -- from A to Z."

Waleed bin Attash allegedly ran an al Qaeda training camp in Logar, Afghanistan, where two of the 19 Sept. 11 hijackers were trained. Osama bin Laden allegedly selected him as a Sept. 11 hijacker but he was prevented from participating when he was arrested and briefly detained in Yemen in early 2001. The Pentagon also says he traveled to Malaysia in 1999 to study U.S. airline security.

Ramzi bin al Shibh, a Yemeni, allegedly helped the German cell of hijackers find flight schools and enter the United States, and helped finance the operation. He allegedly was selected to be one of the hijackers and made a ''martyr video," but was three times denied a visa at the U.S. Embassy in Berlin. A military, court-appointed medical panel has found he suffered from mental illness in the past and may still.

Ammar al Baluchi, also known as Ali Abd al Aziz Ali, is alleged to have sent approximately $120,000 to the hijackers for their expenses and flight training, and helped nine of the hijackers travel to the United States. He is believed to have served as a key lieutenant to Khalid Sheik Mohammed in Pakistan. He was born in Pakistan's Baluchistan province, raised in Kuwait, and is KSM's nephew. His U.S.-educated wife, Aafia Sidiqqui, is in federal custody in New York.

Mustafa Ahmad al Hawsawi, a Saudi, is alleged to have helped the hijackers with money, Western clothing, traveler's checks and credit cards. Hawsawi served as a witness in the Zacarias Moussaoui trial, saying he had seen Moussaoui at an al Qaeda guesthouse in Kandahar, Afghanistan, in the first half of 2001, but was never introduced to him nor conducted operations with him.

Army Col. Stephen Henley is the trial judge. A military judge since 1998, he took over the complex conspiracy mass murder case in November 2008, five months after the men were arraigned. Henley got his law degree, specializing in environmental law, from George Washington University. He was earlier assigned to preside in the military commission case of an Afghan accused of throwing a grenade at U.S. forces in Kabul in December 2002, and in that case became the first commissions judge to exclude a confession on grounds the U.S.-held detainee had been tortured, in that instance by allied Afghan police. He has prosecuted felonies in the DC Superior Court as a special assistant U.S. Attorney in the DC Superior Court, from 1990 to 1991 and has been a military judge at Fort Hood, Texas, Manheim, Germany and Fort Bragg, N.C. He also presided at the 2007 Fort Meade, Md., court martial of an Army officer accused in the case of abusing detainees at Abu Ghraib, Iraq.