I apologize if this was mentioned, but shouldn't there be audio samples from Trayvon for voice comparison? I think this has been asked elsewhere, but why have we never heard his voice?
EDIT: And yes, I know that TM couldn't give a voice sample after death. No voice mail? Videos? Nothing? Was there any mention of investigators attempting to get voice samples of him? It would seem pretty important considering how significant who was screaming is. I think there would be some mention.