I am not an attorney, but this looks like a straight forward Terrorism case.
Now think about this. Both Civilians and military were killed. The civilians were under contract with the military from what I have heard.
As far as the civilian deaths are concerned, that could very well qualify for the case to be tried in a Civilian Court. In Texas, I can predict the outcome of that type of trial.
Normally Federal trials with death penalty convictions take longer than it does in Texas. But that is not always the case, case in point McVeigh. That was a relatively short time between conviction and execution.
Answer: I simply do not know.
SO... maybe he will be tried in a federal court, a CIVIL trial in Texas.
Frankly, my own prediction is that if he ever awakens from his coma, and is not severely brain damaged, that he will be declared psychiatrically unfit to stand trial and will live out his life as some VERY nice maximum security hospital which has all imaginable immenities.