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 Texas, the criminal offense of sexual assault of a child is defined under Texas Penal Code Section 22.011. The law states that an adult commits this offense if they knowingly or intentionally engage in various sexual acts with a child, including penetration or contact involving the sexual organs, anus, or mouth of the child or the perpetrator. A child, in this context, is defined as anyone under the age of 17. It is important to note that under Texas law, ignorance of the child's age is not a defense; the offense is considered strict liability in regards to the age of the child. Conviction of sexual assault of a child can result in significant legal penalties, including imprisonment, fines, and mandatory registration as a sex offender.