RIP
in Boston, we've had a few "one punch homicides". it's pretty much always the head bouncing off the pavement, not the punch.
local fighter (and friend) Jason Giraud was attacked by some guy and accidently killed him with one punch this way. one good shot, reasonable force for self defense, the guy fell, and his head bounced off the pavement.
even though it was a clear cut peice of self defense, Jason went through hell trying to prove it (self defense is an affirmative defense, innocent-until-proven-guilty doesn't apply).
he couldn't raise bail and had to do 8 months committed while awaiting trial. had to reschedule his wedding and all kinds of $hit.
a lot better than being the dead guy i guess, but you can't start a fight and not expect to get hit back.