Allow me to help you out a bit. The responsibility to retreat is the letter of law in many states, basically this means that a victim of a crime had a duty to try and get away from an attacker in any way possible before using deadly force. The burden of proof was put on the victim and the victim would have to potentially endanger themselves or suffer further abuse in order to protect the attacker from death or serious bodily injury. A group of smart guys got together one day and said “man, that doesn’t make sense at all” and wrote the “stand your ground” law which acts much like the castle doctrine. This places the legal burden upon the attacker and shifts the potential for harm or bodily injury from the victim to the attacker. The core of this law basically is that an attacker is responsible for their own conduct and also the conduct of their victim as a result of their "deadly" felonious assault rather than the other way around. It also assumes the victim has every legal right to be where they are, secure in their person, as the attacker does. As much as we all like a sense of fair play, the right to use deadly force to defend yourself is based upon a very specific criteria. That the threat was imminent (or already occurring) and that the threat was potentially deadly or could result in serious injury. What is NOT a legal consideration is “who started it”. For example you are punched in the face in a bar (assault) and you respond by trying to stab the guy in the neck with a beer bottle (deadly assault) and he shot you while you were doing so. He would be in the clear for the shooting but still may face charges for the initial assault (the punch) which would likely be misdemeanor assault. Who started it is irrelevant to the shooting…what is relevant is at what point the confrontation became deadly and who was committing the deadly conduct. Zimmerman is responsible for the initial contact BUT, that means nothing as legally Zimmerman had a right to be where he was and Trayvon had a right to be where he was. Both men had a right to be there. Second, Zimmerman was licensed to carry that weapon concealed, the weapon was legal. He did not exit the vehicle gun in hand (which would be brandishing) nor did he point the weapon at Trayvon when he did so (that would have been either deadly conduct or assault with a deadly weapon). The presence of a weapon was unknown to Trayvon or he likely would have mentioned something about it when he saw Zimmerman following him. I doubt Trayvon would have attacked a man with a gun in his hand. Third, the mere presence of someone cannot legally be called “escalation” if they have a legal right to be there and are otherwise acting in an orderly fashion. But in a more pragmatic sense, if it made Trayvon nervous and Trayvon began to act disorderly then it would be Trayvon who is legally in the wrong, not Zimmerman. Again, who attacked who first? Unknown. Regardless, at the point that Trayvon began to slam Zimmerman’s head into the ground he was performing “deadly conduct” and Zimmerman shot him. If a jury agrees that Trayvon did slam his head into the ground, case closed…it will be “self defense”…unless the DA can prove that Zimmerman intended to kill Trayvon during the fight “just because”. The prosecutor would have to prove that either getting your head slammed on the ground is not deadly conduct or that it never happened. There MAY be a case if the prosecutor can prove that Zimmerman baited Trayvon into deadly conduct so that he could shoot him but that would more appropriately be classified as malice aforethought and make this a murder 1 case. The only other legal route would be for the prosecution to redefine the interpretation of the law to basically negate itself if the shooter committed the initial assault...however that would be a reeeeaaaalllll stretch. I am very curious to see what angle she takes on this. Whether what Zimmerman did was moral, right, just or smart is debatable but given the fact as I understand them now, it sounds like self-defense. But then I was quick to rush to judgment once without all the facts which to this point have not been fully disclosed. We will learn more as the trial goes on but for now, it looks like the prosecutor has a tough road ahead of her.