I think it's impossible to be able to tell truth from fiction in this day and age. You used to be able to trust the media, but I find it increasingly more difficult to trust anyone anymore.
These are the alleged facts that I heard:
1. Eyewitnesses describing color of clothing to back that Martin was on top of Zimmerman.
2. Lacerations on Zimmerman's head (front and back), broken nose, and bruising.
3. No marks on Zimmerman's hands, bruises and marking on Martin's hands and knuckles.
4. Recorded audio of screaming and yelling coming from the site of the fight. Nobody knows who it was exactly, but apparently other eyewitnesses said they had heard Zimmerman yelling.
I also heard that when Martin's parents heard the yelling on the audio, they could not decipher it as their sons. It wasn't until someone got in their ear that they decided that it was their son's voice. I don't know how true that is, but there seems to be a lot of inconsistencies in this case.