Wow, you're either really classist or racist for assuming Martin was set up for a life of crime, and you're definitely a huge fucking moron for thinking there's not enough evidence to convict Zimmerman of, at the very least, manslaughter. It's pretty easy to find out whether it was his gun used in the crime, and it's pretty easy to comb the area around the body searching for anything Martin could have used as a weapon (hint: there weren't any).
If you never did anything even remotely illegal when you were young then you're an anomaly, nobody deserves to be killed for it (except maybe you for having such awful, awful opinions).