A person generally commits the criminal offense of sexual assault of a child—regardless of whether the person knows the age of the child at the time of the offense—if the person (1) causes the penetration of the anus or sexual organ of a child by any means; (2) causes the penetration of the mouth of a child by the sexual organ of the person; (3) causes the sexual organ of the child to contact or penetrate the mouth, anus, or sexual organ of the person or another person; (4) causes the anus of a child to contact the mouth, anus, or sexual organ of the person or another person; or (5) causes the mouth of a child to contact the anus or sexual organ of the person or another person.

The naming and definition of the criminal offense of sexual assault of a child varies from state to state. These criminal offenses are generally located in a state’s statutes—often in the penal or criminal code.

In California, the criminal offense of sexual assault of a child is addressed under various statutes, primarily in the Penal Code. The state defines several forms of sexual assault against children, including acts of penetration or contact involving a child's sexual organs, anus, or mouth, as described in the scenario. These offenses are considered forms of lewd or lascivious acts with a child under California Penal Code Section 288. The law does not require the perpetrator to have knowledge of the child's age to be charged with the offense. Additionally, California recognizes the crime of statutory rape under Penal Code Section 261.5, which criminalizes sexual intercourse with a minor who is not the spouse of the perpetrator. The severity of the charges and the penalties upon conviction can vary based on the specific circumstances of the offense, including the age of the child and the nature of the act. Penalties can range from misdemeanor to felony charges, with consequences including imprisonment, fines, and mandatory registration as a sex offender.