The man who wasn't there, or was he?

Mamdouh Habib, finally released from Guantamo Bay, has returned to Australia. This hasn't stopped Ruddock and Downer from persistantly proclaiming Habibs guilt, even though he was never charged or convicted of any crime. This evening I heard Ruddock state that Habib had prior knowledge of the 911 attack, is it believable that the Americans would have ever let Habib go if they believed this to be true. Only very high ranking al-Qaeda figures would have known about the 911 operation and I doubt there are many people in Guantamo in this category.
Although Billy Bob Thornton is a great actor, Ruddock would have been a natural to play the souless barber Ed Crane in the Coen brothers film The man who wasn't there