Maybe an injury, maybe dirt... no idea. The video is just too crappy to tell. I do see something though, and I don't see any reason why the officer looked pointedly at the back of his head if there was nothing at all there to see.

I find it far more interesting that Zimmerman claimed he received an injury to the back of his head by repeatedly having his head slammed into the sidewalk. I would think if that was the case then he would have gone straight to the hospital to rule out any possible dangerous head trauma... even a rather small blow to the head can be devistating. Both police and EMT's are well aware of that, and I find it interesting that the injury he sustained was so unimportant as to not warrant his being taken immediately to the hospital. Personally, I think he likely got it by slipping on grass wet from the rain and fell... maybe from a scuffle with Martin or maybe all on his own. I could be wrong, but slipping on the wet grass and falling just seems more plausible to me. I definitely don't believe his head was repeatedly bashed on the sidewalk by anyone. I don't believe that the police believe that either.