The two "enemy combatants" who were the first victims of the policy of deliberate ill-treatment cannot be prosecuted because of the illegal way they were interrogated almost a decade ago. Saudi inmate Maad al-Qahtani and Mauritanian Mohammed Ould Salahi are among the 172 prisoners languishing indefinitely at the internment camp in Cuba despite Barack Obama's attempts to close it down. Qahtani has been there for over nine years.

The US military still claims Qahtani to be a would-be "20th hijacker" who narrowly failed to get into the US in time for 9/11, when teams of terrorists seized control of planes and flew them into the World Trade Centre and Pentagon. The prisoner assessment file claims: "Although publicly released records allege detainee was subject to harsh interrogation techniques in the early stages of detention, detainee's admission of involvement in [Osama bin Laden's] special mission to the US appear to be true and are corroborated in reporting from other sources."

The file adds: "He has admitted using a cover story and continues to withhold information of intelligence value."

The records make similar claims about Salahi, claimed to be head of an al-Qaida cell in Germany and recruiter of three of the 9/11 hijackers. He was arrested at his home in Mauritania, rendered to Jordan for eight months, passed on to the US interrogation unit at Bagram in Afghanistan and finally shipped on to Guantánamo in July 2002. He was subjected to the same range of deliberate maltreatment at Guantánamo detailed in 2005 by a military investigation, the Schmidt-Furlow report.

Once again the Guantánamo authorities refused to accept that information obtained through torture is unreliable. Salahi's classified assessment file, dated 3 March 2008, says: "Analyst note: Detainee is determined to be highly credible, notwithstanding … the Schmidt-Furlough [sic] report ... Given the extensive reporting provided by detainee, he remains one of the most valuable sources in detention at JTF-GTMO. He has been highly co-operative and continues to provide valuable intelligence."

(Salahi brought an action against the US government for illegal detention in 2010 in which he claimed his association with al-Qaida ended after 1992 and any incriminating statements he had made should be disregarded because of the mistreatment he had suffered.)

The interrogation techniques first used on Qahtani in 2002 and then repeated on Salahi were bluntly described as torture by the top military judge overseeing the Bush-era military tribunals at Guantánamo. "We tortured Qahtani," Susan Crawford told the Washington Post reporter Bob Woodward in 2009. "His treatment met the legal definition of torture. And that's why I did not refer the case for prosecution."

A Senate inquiry reported: "Military working dogs had been used against Qahtani. He had also been deprived of adequate sleep for weeks on end, stripped naked, subjected to loud music and made to wear a leash and perform dog tricks." During his 20-hour continuous interrogations, which were repeated for 48 days, he was also chained in stress positions, screamed at, had water dripped on his head and was chilled using air conditioning.

The maltreatment he suffered was so severe that his heart rate crashed and he had to be treated in hospital. Permission for waterboarding was sought at Guantánamo, but not used on Qahtani.

His interrogation plan was the first experiment at Guantánamo in adopting illegal Chinese methods previously used against US servicemen in the Korean war of the 1950s. The use of "enhanced techniques" was signed off by Donald Rumsfeld, despite protests from the army and FBI who said the methods were illegal.

The techniques later migrated from the so-called "battle lab" of Guantánamo to the more conventional theatres of war in Afghanistan and Iraq, where prisoners were supposedly entitled to the protections of the Geneva conventions. This ultimately led to the scandal of inmate maltreatment at Abu Ghraib, which fuelled hostility throughout the Arab world.