I'm with 1KM on this one. I don't think Zimmerman had justification to follow Martin, since he didn't see Martin do anything wrong. Seems like he was profiling, and while that can be a useful tool, I don't think it justifies following someone. If I was walking down the street in a black neighborhood, and a random black guy sitting in a car started following me, I'd feel threatened. Martin is dead now, and cannot defend himself, so we only have Zimmerman's and bystanders' accounts of the incident. I do feel that Zimmerman, by getting out of his vehicle with the specific intention of following Martin, did provide the first spark in escalating tensions that led to Martin straddling and beating Zimmerman, and Zimmerman drawing and firing his pistol. I do not believe that Zimmerman meant for things to escalate nearly to that level, but I do not see how he had any business following a guy just walking down the street.
If there had been other things in Zimmerman's mind, such as recent serious crimes (robberies, thefts, assaults, whatever) in his neighborhood by black males, then perhaps profiling would have been enough to follow, at a distance, just to make sure Martin didn't suddenly disappear into someone's yard. Unless Martin did something illegal, he had every right to walk down the street unmolested by Zimmerman physically or emotionally. I would have voted manslaughter if I had been on the jury, if everything I just described is how the incident actually happened.