So put him on trial !!!

Well, then, it is time, has been for a long time already, to put this fellow on trial, to "bring him to justice", which means to put him before a court of law for proceedings on the charges against him. Now that he's confessed, not even the bushbaby playpen should have anything more against doing justice in this case! Let a judge and jury determine his guilt (or innocence) and the sentence to which he may be condemned.
The civilized world must show it can exercise justice even against those committed to destroying that very system!

The New York Times
National
Suspected Leader of 9/11 Attacks Is Said to Confess
By ADAM LIPTAK
Published: March 15, 2007
“I was responsible for the 9/11 operation, from A to Z,” Khalid Shaikh Mohammed said, according to a Pentagon transcript.

And here is the link to the partially censored transcript made available by the Pentagon.