People v. Russell
California Court of Appeal, Sixth District
144 Cal. App. 4th 1415 (2006)
Philip Russell (defendant), a homeless man, found an old, rusted, tagged-out motorcycle sitting unlocked near a repair shop's trash bins and, believing it abandoned, took it, later bringing it back for repairs. A police officer gave Russell the registered owner's name and told him to get the bike titled in his own name; Russell tried, unsuccessfully, to contact the owner, who by then had moved. Russell was later charged with and convicted of possessing stolen property, and he appealed, arguing the jury should have been instructed that a good-faith belief the motorcycle was abandoned would negate the knowledge element.
Whether a mistake or ignorance of fact or law may be a defense to a crime if the mistake negates a required mens rea or knowledge element of the crime.