Does the third party witness know?
I don't know. I was just saying that other witnesses may be more useful than Zimmerman's father.
As for this report, it's of the same value as the "no wounds on his head" conclusion, based on a grainy police video. It's jinned up (using 'jin' as in "genie") noise to get attention to the media. When the rubber meets the road, this experts testimony would be subject to lots of scrutiny.
Notice he can't rule in Trayvon, so he's left us a mystery. If you're the jury, you have to look at other evidence. Zimmerman is banged up, Martin isn't. Who was winning the fight? Who is more likely to be yelling for help?