I think it is pretty clear that at worst, this was an accident; meaning that George Zimmerman did not have the intent to kill someone when he went out that night, or when he followed Trayvon Martin. As Martin's mother said on the Today show, things got out of control.
That does not mean that Zimmerman is not guilty of unjustifiable homicide, although I can't see any reasonable charge greater than manslaughter.
The real question here is whether Zimmerman is culpable and to what degree for the fight he had with Martin. If Martin attacked him on his way back to his vehicle, then he is innocent. If he accosted Martin and Martin responded by hitting him, then he is responsible - it should be pointed out that it is possible that Martin acted in an inappropriate, or even criminal way without Zimmerman being entirely innocent; if Zimmerman escalated the encounter and then Martin escalated it further, neither would be completely non-culpable (at least as I reckon it, I don't know enough about the relevant law to offer a good legal opinion, but I assume that two people can get into a fight without either being considered innocent).
It seems to me that the people on both sides of this (as a political issue, I am not talking about people directly involved with the case) are taking positions somewhat based more on fear and resentment rather than on trying to determine the truth.
Those who insist that Zimmerman was just a hothead and that Martin was a choirboy are, I think, terrified of being accosted by a non-cop and not knowing how to respond; should they run in case it's a mugger, or should they stand still for fear that the police will side with the accoster? And I suppose some blacks are genuinely scared that we are going to see legitimized lynchings by overzealous neighborhood watches.
On the other hand, those who want to completely trash Martin are scared ultimately that if Zimmerman is not acquitted, that it will send the signal that it is unacceptable to defend one's self. The great fear is that people under attack by thugs (and let's be honest, in particular black thugs) are now going to hesitate to defend themselves and get killed, or are going to be sent to prison for self-defense. Moreover, thugs will be aware of this and use it to intimidate people.
I personally think that the best thing to do in this case is to try to find the truth, regardless of what narrative it fits.
That is all.