A person generally commits the criminal offense of public lewdness or lewd conduct in public if the person knowingly engages in any of the following acts in a public place—or, if not in a public place, the person is reckless about whether another is present who will be offended or alarmed by the person’s (1) act of sexual intercourse; (2) act of deviate sexual intercourse; (3) act of sexual contact with a person’s own private parts or those of another.

Public lewdness laws vary from state to state, and some states define and charge such criminal offenses under indecent exposure laws. Public lewdness is usually a misdemeanor offense, but may be a felony offense under some circumstances. And in some states a conviction for public lewdness may require the defendant to register as a sex offender.

In Montana, the offense of public lewdness is typically addressed under the state's indecent exposure laws. According to Montana Code Annotated (MCA) 45-5-504, a person commits the offense of indecent exposure if they knowingly or purposely expose their genitals under circumstances in which they know their conduct is likely to cause affront or alarm in order to abuse, humiliate, harass, or degrade another or to arouse or gratify the person's own sexual response or desire or the sexual response or desire of any person. This includes acts of sexual intercourse, deviate sexual intercourse, or sexual contact in public places, or in private where there is a risk of public exposure. Indecent exposure is generally considered a misdemeanor in Montana, but it can be a felony for a third or subsequent offense, or if the person exposed themselves to a minor. A conviction for indecent exposure may also require the defendant to register as a sex offender, depending on the nature of the offense and the age of any victims involved.