Jorge M. (defendant) was a minor who was on in-home probation for a drug offense. When police officers conducted a home inspection pursuant to probation, they found three rifles and a semiautomatic rifle with a banana-clip magazine in the area of the house where Jorge had indicated he kept his personal belongings. Jorge was charged with possession of an assault weapon and firearm possession in violation of his probation. The assault-weapon-possession statute criminalized the possession of certain types of assault weapons but did not specify any mental-state element of the crime. The juvenile court adjudicated Jorge a ward of the court and sentenced him to a juvenile-camp program. The court of appeal reversed the ruling, holding that the assault-weapon-possession statute contained an implicit mental element of actual knowledge of the weapon’s illegal characteristics and that there was insufficient evidence to prove that Jorge had this required knowledge. The attorney general’s petition for review to the Supreme Court of California was granted.