When you listen to Zimmerman calling the police and the police officer on the phone telling him not to pursue Martin; it's game over in my mind. It's on the Wiki page about the incident.
If the police tell you not to do something and you do it and what you did results in the death of another, you're in a heap of trouble and you should be. They are the law enforcement authority and its as simple as that.
Now...all that being said; Zimmerman is being charged with murder, right? Not wrongful death...murder. Does what Zimmerman do rise to a murder conviction? I think so but I can see where the prosecution may be over-reaching with the murder charge.
When Zimmerman was instructed to stop his surveillance pursuit in which he embarked upon, and this while he had the police dispatcher on the phone, and the operator/dispatcher heard this pursuit of Zimmerman running along with his heavy breathing, didn't he Zimmerman say "Ok" and then stopped the pursuit right then ? Isn't this where Zimmerman said next that as he walked back to his vehicle Martin then approached him ? I am vague on my recollection of it all now..
I assume it's possible.
The logic of it though is a bit weird...if you get out of your car to pursue someone you are, by definition, between the person you're looking for and your vehicle. Right?
You would have to be in pursuit for quite a while to have the guy you're following get back between you and your vehicle.
Sounds pretty far fetched but possible? Sure.
Also you have to look at how Martin is being portrayed....if he was up to no good and so on and so fourth...is the guy really going to circle back? If I'm running from someone and they stop chasing me...I'm not coming back to engage.
Still; it's anyone's guess, only 2 people know the circumstances and what happened. One is dead, one is on trial for killing him.