ron is reporting and sara horowitz is an investigator from the "washington post." >> the surveillance camera does pack a lot of apparent information showing no damage to this man who claimed ha tof been brutally beaten by the man he killed. >> a couple things, chris, first, the tape, what you're seeing is 40 minutes or so after the gunshot was fired. it's pretty soon. zimmerman's defenders emphasized he was treated by paramedics, at the scene in the back of a police car and he was, as you say, cleaned up. that's why you don't see blood, they say. also, we were able to zoom into the back of his head and there is some sort of abrasion. on the back of his head, which seems to suggest and give more credibility to his story. ultimately, the bottom line is how much bodily harm do you have to endure before you can legally fire a gun in self-defense in this state. witnesses said they did see martin on top of zimmerman. there was some kind of fight witnesses say. you have to put all the pieces to the puzzle together. a lot of people are saying, don't rush to do many conclusions because of this