I've been waiting for people on this board to support their claims that Martin assaulted Zimmerman first (or even for claims of the reverse). Evidence has never materialized.
In their zeal, people tend to forget that.
Since we don't have a video of the physical altercation beginning, we can never know to a complete certainty who attacked who first.
Nonetheless, there have been some very compelling data points which indicate it was Trayvon who attacked Zimmerman not only
first, but exclusively:
1.) Who had injuries and who did not.
2.) Zimmerman's account which he offered immediately, which police found credible, which a jury found credible, which two voice stress analysis tests detected no deception during, and which fit well with the totality of physical and witness testimony. An account he was prepared to go back to the scene the following morning and relate in detail, on video, with multiple detectives accompanying him (a highly unusual thing to do, and not the expected actions of someone engaging in deception they'd quickly come up with on the fly and would have no reason to think would hold up under that kind of scrutiny.)
3.) Rachel Jeantel telling Huffington Post after the verdict that she thought Trayvon "swung first" and that she did not believe Zimmerman had his gun out. She also told Piers Morgan on CNN around that same time that what had happened to Zimmerman was "rear whoopin'" which he received because he was "actin' like police, or security" which seems to indicate what I always suspected, which is that Trayvon got irritated, not scared, and attacked Zimmerman for keeping an eye on him, not out of self-defense.
4.) The screams all sounded like they came from one person, and that that person was involved in a completely lopsided, unidirectional assault rather than a back and forth, give and take fight.
5.) Witness 11 and other witnesses at the top of the "T" intersection area said they heard a brief exchange between two people, one of whom sounded meek and the other sounding angry and confrontational and that this rapidly transitioned into a physical altercation which then rapidly moved southward down the path, terminating at the area the screaming and gunshot were about to come from. This all fits Zimmerman's account of events perfectly as well as a narrative of a one sided assault/chase.
6.) Zimmerman had just summoned the police to the area and had even expressed impatience when he said "just get an officer over here" at the point where Trayvon circled his truck. So you've got someone who knows law enforcement are coming and would therefore have a very strong incentive to avoid doing any illegal actions like an assault.
Is any of this definitive? No. Is it wordy and rambling? Yep.
Even so, I think there are some compelling reasons to lean toward thinking Trayvon attacked first.