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 South Dakota, the criminal offense of sexual assault of a child is addressed under the state's statutory laws, specifically within the South Dakota Codified Laws (SDCL). The statutes define various sexual offenses involving minors, which can include rape, sexual contact with a child under sixteen, and sexual exploitation of a minor, among others. The law does not require the perpetrator to know the age of the child for the act to be considered a criminal offense. The offenses encompass acts where there is any sexual penetration or contact, as described in the provided scenarios, involving a child. The severity of the charges and the penalties upon conviction can vary based on factors such as the age of the child, the age difference between the offender and the child, and the nature of the act. Convictions for such offenses typically result in serious consequences, including lengthy prison sentences and mandatory registration as a sex offender.