dr. mark siegel who's in texas.isoner, was also in the van on the other side of a metal partition. apparently they have those so they can't hurt each other and according to "the washington post" the other prisoner heard gray do what he said sounded like he was intentionally trying to sbir himself. how badly could somebody injure themselves in the back of a police van like that? >> steve, you could sustain a brain injury and you could get a head injury that way and a neck injury. there's no way that you could sever your spine bashing your head into the wall or the side of a car or anything like that. that is not the cause of a severed spine in this case. >> right. so no matter how hard you try, you can't do it. we remember the quarterback that banged his head in celebration and sprained his neck with a helmet on. >> exactly. >> so it seems implausible he hurt himself severely. >> he may have hurt himself but not to the extent where he would sever his spine. no chance. >> okay. doctor, you're down in crawford, texas,