You're 'allowed,' but guessing that he'll get the death penalty and be executed just makes you look silly. That has nothing to do with Zimmerman, btw, I just think it's silly because of how hard it is to get the death penalty and be executed. People commit far more heinous crimes, involving raping and torturing their victims before murdering them, and they commit those crimes with far more premeditation and yet they mainly get life sentences. Even when they get the death penalty, there is almost never any actual execution.
I don't know if he'll be freed or not, and personally, I won't speculate about that. I still don't think we'll ever know for sure exactly what happened.
But the idea that he'll get the death penalty *and* be executed is pretty far-fetched, even if he is completely guilty about everything you've said he is guilty of.