|Khalid Sheikh Mohammed after his capture in Pakistan |
At the time of his capture in Rawalpindi, Pakistan, in 2003, Khalid Sheikh Mohammed was one of the world's most wanted men.
Accused by the US of being the mastermind of the September 11, 2001, attacks, he was said by US officials to be the third-in-command of Osama Bin Laden's al-Qaeda network.
Charged on February 11 with war crime, murder and conspiracy at a military tribunal in Guantanamo Bay in Cuba, he faces the death penalty if convicted.
However, his supposed confession, in which he was alleged to have admitted planning the 9/11 attacks to the 2002 Bali bombings and scores of other crimes, was obtained under the controversial interrogation technique of waterboarding, the CIA admitted earlier this year.
Many details of Mohammed's life are hard to verify.
Born in either 1964 or 1965, reportedly in Kuwait to Pakistani parents, Mohammed grew up in the Gulf state before returning to Pakistan.
After reportedly joining the Muslim Brotherhood at the age of 16, he moved to the US, attending a Baptist college in the state of North Carolina and later graduating from the southern state's A&T University with a degree in mechanical engineering in 1986.
He is then thought to have gone to Afghanistan to join the country's "mujahideen" fighters in their battle against the Soviet Union's invasion.
At some point during this period, either in Afghanistan or in Pakistan, it is believed he first came into contact with the man who would later shape much of his later life - Osama Bin Laden.
He also travelled to the Philippines, Qatar and Sudan.
He first came to US authorities' attention in 1995, over the so-called Boijinka operation in which Mohammed and several others are alleged to have plotted to blow up 12 passenger flights over the Pacific ocean.
The plot was uncovered and foiled, and he was secretly indicted for his alleged role in the bombings by a New York court.
According to the US commission on the September 11 attacks, Mohammed was reportedly regarded as an effective leader.
"Co-workers describe him as an intelligent, efficient, and even-tempered manager who approached his projects with a single-minded dedication that he expected his colleagues to share," the report states.
Unlike bin Laden, he was reportedly fond of staying in expensive hotels and visited nightclubs during his time in the Philippines.
The US report accuses Mohammed of planning the September 11 attacks as early as 1998 after he joined bin Laden's al-Qaeda network.
In March 2003, US and Pakistani agents seized Mohammed in a pre-dawn raid in Rawalpindi, near the capital Islamabad.
At the time of his capture, the US reward for information leading to his arrest had risen to $25m.
In 2006, Mohammed was reportedly transferred from an unknown facility to the US detention facility in Guantanamo Bay, Cuba, although there were reports he had been held in a prison in Jordan.
In March 2007, Mohammed testified before a closed door hearing at the facility in order for the US to determine whether he was an enemy combatant.
In partial transcripts released by the US, he allegedly said he had been responsible for a string of deadly attacks, including those in New York and Washington in 2001.
"I was the operational director for Sheikh Osama Bin Laden for the organising, planning, follow-up and execution of the 9/11 operation" he was quoted as saying.