Hey B, WELCOME!
ITA with what you mean by the bruising showing up right after a fight.
HOwever, I don't believe that GZ ever had his backside on the ground having his head smashed into the ground. Did you see the pics of GZ backside? No grass stains, mudd, water, no nothing. IMO, he was never on his back. So I've been wondering what could've caused the injuries to the back of his head? IMO, GZ may have been pushed up against something while standing up. If him and Trayvon were pushing and shoving, it's possible GZ backed up into something and as Trayvon was pushing him trying to get away as GZ had a hold on him, GZ head was knocked up against something repeatedly. Does that make sense?
I picture GZ struggling to keep hold of Trayvon as he is pushing trying to get loose. I picture Trayvon pulling back and falling with GZ landing on top of him. IMO, that's how they ended up on the ground...but GZ never was on the bottom.
If Trayvon gave GZ such a beating with his "hands" wouldn't you expect to see bruising or something?
JMO and again WELCOME!