Precipitation is irrelevant if in fact Trayvon was on top of Zimmerman punching him when the fatal shot was fired.
And the Grand Jury might even agree. Or not. But if you want to minimize your chances of going to prison, you might want to take the "precipitation" factor into account.
Zimmerman might spend years in prison, due to that "precipitation."
Wrong, if the kid was tying to save his life from a mugger and the mugger broke free and shot him what would be the result. On top does not mean anything other than the kid was fighting for his life from a stalker he did not know.