I don't advocate a trial for a non-citizen terrorist who had 253 witnesses to his crime.
If there are 253 witnesses, then why on earth would it be so hard to convict the guy? What is there possibly to fear? If we have what is supposedly the best system for sorting the guilty from the not guilty, why the sudden lack of confidence when it comes to those who want to do us harm, especially when the evidence seems to be overwhelming?
Everyone gets a trial. Everyone gets a lawyer. Unless we want to go the Alice In Wonderland
rules: "'No, no!' said the Queen. 'Sentence first--verdict afterwards.'" Our adherence to the rule of law is supposedly what makes us different from "them" and what makes this country worth defending in the first place.
As for "execute," I'm against executing anyone, but that's another topic. I'm certainly against executing anyone before a trial. Talk about being "judge, jury, and executioner..."