The injuries would have been significant if Martin had pinned Zimmerman on the sidewalk and continued banging his head into the concrete. Once he causes a brain hemorrhage, it would have been light out for Zimmerman. However, Zimmerman, knowing some martial arts skills shifted his body over to the grass. When he did that, his shirt hiked up exposing the gun. When Martin spotted the gun, Zimmerman knew if he didn’t get control of the gun, Martin would be grabbing for it. A fight for the gun was something Zimmerman could not afford to lose. So, he shot Martin because it was his last chance to save his own life.
The medical examiner should have been asked if her experience as an examiner has had people who died from head trauma from having someone bash it into a concrete surface.
I’m guessing that will come up if it hasn’t yet.