On a large tract of uninhabited and untilled land in a wooded and sparsely populated area of Michigan, P established a practice bombing range over which the Air Force dropped simulated bombs at ground targets. The practice bombs were metal cylinders about forty inches long and eight inches across, filled with sand and enough black powder to cause a smoke puff by which the strike could be located. Signs read 'Danger - Keep Out - Bombing Range.' Nevertheless, the range was known as good deer country and was extensively hunted. Spent bomb casings were cleared from the targets and thrown into piles 'so that they will be out of the way.' They were merely dumped in heaps and many of the heaps had been accumulating for four years or upwards. The casings were exposed to the weather and rusting away. D went hunting in this area but did not get a deer. He thought to meet expenses of the trip by salvaging some of these casings. He loaded three tons of them on his truck and took them to a nearby farm, flattened them and trucked them to market in Flint, he realized $84. D was a fruit stand operator in summer and a trucker and scrap iron collector in winter. He was an honorably discharged veteran of World War II and had a clean criminal record other than one charge of reckless driving. D did all his acts in the open and voluntarily and promptly admitted the true facts to the investigating authorities. He had no intention of stealing but thought the property was abandoned, unwanted and considered of no value to the Government. D was charged with violating 18 U.S.C. Section 641 making it a crime to knowingly, willingly and unlawfully to steal and to convert government property. D's defense was that he honestly believed that the bomb casings were abandoned. The court refused to submit or to allow counsel to argue to the jury whether Morissette acted with innocent intention or that the casings were abandoned. The trial court rejected that defense and instructed the jury that the question of intent is whether or not he intended to take the property. This was because D knew that he was on government property without permission. The trial court stated the issue of intent was simply whether or not D intended to take the property and that D’s felonious intent was presumed by his own acts. D was found guilty, fined and sentenced to prison. The court of appeals affirmed; knowing conversion did not include an element of the criminal intent because none was expressly required by the statute. This conclusion was thought to be required by the failure of Congress to express such a requirement and this Court's decisions in United States v. Behrman, 258 U.S. 280, and United States v. Balint, 258 U.S. 250. The Supreme Court granted certiorari.