I didn't have time to follow up to this earlier, but I did a bit of reading.
Have you actually read the law, or are you repeating someone's convoluted interpretation?
I read the law:
776.013 Home protection; use of deadly force; presumption of fear of death or great bodily harm.
#1 is the one that addresses "reasonable fear". But, the subsequent (a) and (b) prerequisites are associated with a dwelling, residence, or occupied vehicle. It wouldn't apply to this situation.
#2 is a set of exclusions for #1. They wouldn't apply to this situation, either.
#3 is the one that applies:
(3) A person who is not engaged in an unlawful activity and who is attacked in any other place where he or she has a right to be has no duty to retreat and has the right to stand his or her ground and meet force with force, including deadly force if he or she reasonably believes it is necessary to do so to prevent death or great bodily harm to himself or herself or another or to prevent the commission of a forcible felony.
I've highlighted the important part: meet force with force. Following someone is not force, and doesn't justify force (or deadly force) in response.
If you haven't read the entire law before now, I suggest you do so, rather than relying on someone else's interpretation (including mine).
Love your tag. ;-)
That section backs up what I mean by "feel threatened." Right now, it's a he said/she said situation. If Zimmerman is being truthful and Martin popped him in the face when Zimmerman merely asked "what are you doing here", then that statute could apply to him.
If Martin's girlfriend is telling the truth and Zimmerman initiated physical contact with Martin, then it could also be reasonable for Martin to fear for his life when a man he knew had been watching/following/looking for him...grabbed him or took a swing at him. Under that scenario, Martin would have no "duty to retreat" could "meet force with force, including deadly force" i.e. taking Zimmerman to the ground and pounding his head on the sidewalk.
All of us are just speculating and offering opinions at this point. Hopefully the police can sort out all the pieces and put together something relating to the truth.