Why Try the Guy?

Forgive me if this seems like a dumb question, but what is the point of putting Khalid Shaikh Mohammed et al. on trial when their convictions are essentially guaranteed? Given that hearsay, coerced testimony, and classified material that neither the defendants nor their lawyers will get to see would all be admissible under the rules the Bush administration wants Congress to approve, is there any scenario in which these guys would be acquitted? And if they were somehow acquitted, is there any scenario in which they would be released?

Since the answer to both questions seems to be no, what chance is there that even a mildly skeptical person will view the trials as fair truth-finding endeavors, let alone the efforts of "a regularly constituted court affording all the judicial guarantees which are recognized as indispensable by civilized people"? And if it's inevitable that these exercises will be seen as show trials, why not just give a speech, maybe with slides, laying out each prisoner's crimes and explaining why it's impractical to try him? Then the president would at least get points for candor.