18 Pa.C.S.A. §3928. Unauthorized use of automobiles and other vehicles.
(a) Offense defined.–A person is guilty of a misdemeanor of the second degree if he operates the automobile, airplane, motorcycle, motorboat, or other motor-propelled vehicle of another without consent of the owner.
(b) Defense.–It is a defense to prosecution under this section that the actor reasonably believed that the owner would have consented to the operation had he known of it.