Well, Mr. Leidner's clueless and didn't take the time to all of read Chapter 776 ("Justifiable Use of Force") of Florida Statutes or he would have found out that Florida allows the use of deadly force the the initial aggressor under certain conditions.
First, Leidner apparently stopped reader at Florida Statutes 776.012(1) ("Use of force in defense of person"), which says, pertinent part:
[A] a person is justified in the use of deadly force and does not have a duty to retreat if . . . [h]e or she reasonably believes that such force is necessary to prevent imminent death or great bodily harm to himself or herself.
If he'd continued for four more sections, he would have found Florida Statutes 770.041(2) ("Use of force by aggressor"), which reads in pertinent part:
The justification described in the preceding sections of this chapter is not available to a person who . . . Initially provokes the use of force against himself or herself, unless:(a) Such force is so great that the person reasonably believes that he or she is in imminent danger of death or great bodily harm and that he or she has exhausted every reasonable means to escape such danger other than the use of force which is likely to cause death or great bodily harm to the assailant; or
(b) In good faith, the person withdraws from physical contact with the assailant and indicates clearly to the assailant that he or she desires to withdraw and terminate the use of force, but the assailant continues or resumes the use of force.
So, Mr. Leidner, it's not that "Mr. Zimmerman will have to show that he was not the initial aggressor." Florida Statutes 776.041 sets circumstances under which an initial aggressor can still use deadly force.
In the early 45-minute press conference, one of Zimmerman's initial attorneys (Hal Uhrig) said that a physical altercation was necessary to trigger this - that following somebody would not. (Given that you were wrong about Florida law, and wrong when you say Zimmerman was 'instructed not to purse' Trayvon Martin, Mr. Leidner, are you certain that Zimmerman has to prove he wasn't the aggressor? Could it be that the state has to show Zimmerman was the aggressor? You're just a law school student, you know. Some of us passed the bar and think enough to read the statute before commenting on it.)
"However, if the prosecution can show that the defendant "provoked" the incident, the Defendant loses his right to claim justifiable use of force."
That's written by Kevin F. Moot, who's a member of the Florida bar and has a criminal law practice in Florida.
You, Mr. Leider, wrote:
"And Mr. Zimmerman will have to show that he was not the initial aggressor."
You're a law student from Connecticut who didn't read the Florida Statutes on self-defense. Forgive me if I take the actual lawyer over the law student, the Florida lawyer over the Connecticut law student, and the criminal lawyer over the law student.