I saw that video and I didn't see any cut on the back of his head either. But it was not a real close up but if he had the kind of cut that his supporters are saying, there should have been some sign of one but who knows. As for his broken nose, no blood there either. He had a jacket on so no way to know if his shirt is bloody but he had just shot a boy at close range so I would imagine blood spatter would be on Z's shirt. We will never know if it is Z's blood or Martin's because the police didn't collect the clothing of Z. Just the boy's.