I guess that means that they don't need to use a grand jury if they aren't asking for the death penalty. If he is sentenced to prison, that could mean death at the hands of another prisoner.
The sixth amendment promises a public and speedy trial "by an impartial jury of the state and district wherein the crime shall have been committed." But if there was no crime committed, he isn't entitled to an impartial jury.
Trayvon Martin Case: George Zimmerman not being charged
http://www.freerepublic.com/focus/f-bloggers/2869453/posts