Trayvon could have sucker-punched Zimmerman without much risk if he'd run away immediately afterward, since self-defense statutes would not allow someone in that situation to shoot the fleeing assailant (a defendant might argue that the impact to his brain caused a momentary loss of judgment similar to that of a "crime of passion"; I think the statutes are grossly defective in not allowing a jury a clear spectrum of culpability they could assign, ranging from slight culpability (the defendant should have used better judgment even in those circumstances, but does not pose a threat to the community) and a 20-year prison term (the defendant had no evil state of mind, but had no particular justification for shooting the decedent).
Personally, I think the world would be a better place if people who sucker punched other people had a slight but significant chance of getting shot. Some otherwise good people who get particularly agitated may sucker punch someone unjustifiably, and it's probably best if most such people don't get shot as a consequence, but sucker-punching should be risky enough as to discourage rational people from doing so.
There should be a law outlawing "sucker punches".
Oh, wait, I know...isn't a "sucker punch" assault or something like that? There ARE laws against "sucker punches"./sarc
Good post, supercat!