Sexual assault is generally forced sexual intercourse, sodomy, or other sexual penetration of another person—against the person’s will and without the person’s consent. And although precise definitions and punishments vary from state to state, the criminal offense of aggravated sexual assault generally includes aggravating circumstances that increase the severity of the sexual assault—such as when the assailant or perpetrator uses, displays, or threatens the victim with a deadly weapon (a gun or knife); when the assailant uses a rape drug to incapacitate the victim; or when the victim is a child under a certain age, as defined by the statute.

In Montana, sexual assault is defined under the Montana Code Annotated (MCA) as knowingly subjecting another person to any sexual contact without that person's consent. Aggravated sexual assault, while not specifically termed as such in Montana law, would fall under the category of Sexual Intercourse Without Consent, which is a more serious offense and is addressed under MCA 45-5-503. This statute covers forced sexual intercourse, sodomy, or other sexual penetration without consent, and includes circumstances that can elevate the severity of the crime, similar to what is described as 'aggravated' in other jurisdictions. Factors that may increase the severity include the use of a weapon, the administration of an intoxicant or a controlled substance to the victim without their consent, or if the victim is a child below a certain age. The age of consent in Montana is 16 years old, and sexual acts with minors under this age can lead to charges of statutory rape or sexual abuse of children, depending on the circumstances. Penalties for sexual assault crimes in Montana are severe and can include lengthy prison sentences, with the possibility of life imprisonment for certain aggravated cases.