prosecution's evidence was insufficient to establish the necessary mens era requirement.

US v. Nieves-Castano, No. 06-1517 (1st Cir. March 27, 2007)
Conviction for possession of a machine gun is reversed and a verdict for defendant ordered where the prosecution's evidence was insufficient to establish the necessary mens era requirement. Conviction for possession of a firearm within a school zone is affirmed over defendant's argument that the statute is unconstitutionally void for vagueness under the Fifth Amendment's Due Process Clause because it fails to specify how to measure the 1000 foot distance from a school that marks the boundary of a school zone. The sentence is remanded for reconsideration in light of the reversal of the first charge.
http://laws.lp.findlaw.com/1st/061517.html