Ohhhh. I see the problem here.
For your information, I don’t think Stand your Ground will be important if this matter goes to trial. If Zimmerman is lying on his back being beaten about the head and face, and that is the moment he uses deadly force, he needs no “Stand your Ground” law to defend himself. He cannot retreat if he is pinned to the ground OR under contemporaneous attack when he fired. It matters not that he was “following” Martin, as it is not unlawful to do so.
You have no evidence Zimmerman “chased” anyone. You are using the word “chase” to cloud thinking. You have no evidence Zimmerman confronted Martin. You say “chased, confronted, shot, and killed” as if to substitute your simple understanding of this event for that of the police officers, detectives, supervisors, and crime scene technicians.
Exactly right. Stand your ground implies the actor had the option to retreat. If Zimmerman became the target of physical force, and was overwhelmed by it, he's lost the option of retreat. "Stand your ground" is an irrelevant concept in a situation where retreat isn't possible.
The facts might lead one to ask if Martin was exercising a stand your ground option.