It seems to me that George Zimmerman's 911 call is an attempt to establish a "self-defense" case for a pre-meditated murder. Take a listen:
If you listen to Zimmerman's 911 call at :58 on this video, you will hear:
"Now he's coming towards me. He's got his hand in his waistband. And he's a black male."
later at 1:21:
"He's coming to check me out. Yep. He's got something in his hands."
I don't know what can be proven legally in regard to these comments. What I do know is that people do put guns in their waistbands. However, Trayvon had no gun, but skittles and an iced tea... And it is quite difficult to imagine anyone putting a can of iced tea or skittles in their waistband.
The use of the term "waistband" to me seems to be Zimmerman creating an evidence trail to show he "feared for his life" so he can legally kill someone under Florida's "stand your ground" law.
I am very curious to see what Zimmerman may have been writing, googling, or chatting about in the months and years leading up to this killing. It would not be surprising to me if mounds of evidence of a long-standing desire to kill someone is present.
This seems like a disturbed individual waiting for an opportunity to carry out some dark fantasy, nothing like a man in fear due the presence of a "suspicious individual."