Khalid Sheikh Mohammed's dramatic confessions before a US military hearing are beginning to backfire on the Bush administration. Legal experts are casting serious doubt about their validity as evidence, and human rights activists say they only illuminate a "sham process" of justice in the US war on terror, including the apparent use of torture on Mohammed and potentially dozens of other al-Qa'ida suspects.

Mohammed's claims to have been fully responsible for the 9/11 attacks on New York and Washington, the murder of Daniel Pearl, the 2002 Bali disco bombings and a host of lesser plots, both hatched and fully realised, were made public to great fanfare last week.

Almost immediately, however, legal experts said he appeared to be exaggerating his role for his own self-aggrandisement and may also have deliberately floated false claims to send US investigators on wild goose chases.

The CIA denies that Mohammed was tortured, but evidence to the contrary has been building for years. Two years ago, a CIA official told ABC News that he had been water-boarded, and had won the admiration of his interrogators because it took him two to two-and-half minutes to start confessing - well beyond the average of 14 seconds observed in others.