If what one post earlier in this thread appears to be true, that of Martin having gun powder on his hands, he may have been to defend himself because Zimmerman may have had his gun out.
Sorry I'm missing your point. If it's shown Martin has powder burns on his hands, what does that tell us other than what we already know, that they were fighting when the shooting happened?
Well, I have not seen where the police have released any lab or autopsy reports, but it would make sense to me that Martin would have residue on his hands. A witness saw him on top of Zimmerman and Zimmerman yelling for help. The witness went inside and then heard the shot.
If Zimmerman pulled out his gun in such close proximity, as it seems clear he did, you would expect Martin to have tried to grab the gun. And this would in fact verify the self-defense claim to the extent that it would show they were still engaged - in other words, Zimmerman did not shoot at a distance or in the back.
Of course, it tells us nothing about who started the fight.