This call for proof by eyewitnesses is infantile. Many many crimes happen without any witness, and yet there can be a prosecution. In this case, ask if Trayvon was committing an assault. Take the evidence you have, knowing that Martin's family is going to sow doubt with speculation, and figure out if you believe Zimmerman.
The burden is on the state to prove otherwise - that's a bit beside the point because, as far as I know, the state has zero evidence that Zimmerman threw the first punch, acted belligerently toward Trayvon, or otherwise endeavored to start or escalate physical violence. It's not that what they have to work with is weak, it's that they have nothing to work with, against Zimmerman. And there is PLENTY to work with, against Martin.
I was just disturbed that the Today Show would AGAIN lie about the situation. As soon as one lie is cleared, another one comes up.