The man, Pakistan-born Kuwaiti Khalid Sheikh Mohammed, has been described as one of those closest to the leader of the al-Qaeda terrorist network, Osama bin Laden.
He was arrested in Pakistan in 2003 as a suspect in the September 11 attacks. He has been held at the US military base at Guantánamo Bay, Cuba, since 2006. The protracted legal process has been dominated by the question of whether the torture he was subjected to in CIA custody has affected the evidence.
During the 2001 attacks, terrorists hijacked commercial airliners and crashed them into the World Trade Center in New York and the Pentagon near Washington, D.C. Nearly 3,000 people died in the attacks.
