With all the evidence that's been released, it's really looking like Zimmerman might walk. From what I've read, the law does not hold up if you provoke an altercation. What's not clear is what exactly is considered "provoking". By following Martin, did Z provoke him? Or was whoever first assaulted the other first at fault? As we only have Z's side of the story, and most of the evidence so far looks to back his story up, if it comes down to the second option, Z will most likely walk. There's really no way for the prosecutor to prove otherwise. And if it comes down to the first option, it's going to be really hard to get a jury to unanimously vote guilty.
I still personally feel Z is responsible for M's death, but if there's no way to disprove his story, then IMO you can't send the man to prison. Due to the fact that as much as I think his whole story is BS, there is a chance he might be telling the truth.