What established facts did I miss? What facts proved who the aggressor was? It was the prosecution job to prove Zimmerman was the aggressor. But the defense couldn't or had to prove that TM was the aggressor. There are no facts that show who the aggressor was. Nothing but hypotheticals. The facts that I know of are as follows:
1. Zimmerman followed TM
2. There was a confrontation
And there was testimony from Zimmerman that the confrontation was initiated by Martin. The physical evidence (bullet trajectory and Zimmerman's injuries) support Zimmerman's version of the events. Furthermore, the neighbor's testimony supports Zimmerman's versions of the events.
That's called credibility building. The Juror who was interviewed after the trial stated that all members of the jury found Zimmerman to be credible in his retelling of the event.
Obviously, you can never be 100% certain on testimony, but the more corroborating evidence presented, the more likely the testimony becomes.
Furthermore, there was no evidence to dispute Zimmerman's testimony. Martin had no physical injuries other than the gunshot wound which suggests that Zimmerman was not able to physical batter Martin.
3. TM got the upper hand in the fight
Literally no evidence to suggest that this was a consented to fight or that Martin was either losing or neutral at one point such that he needed to get the upper hand.
4. Zimmerman shot TM
5. TM died.