Perhaps you just meant it as a prank among friends. Or maybe you were really mad and meant to insult a neighbor. Does that intent matter under state laws on indecent exposure? Do your bare buttocks count as "genitals" under state statutes?
Here's what you need to know about mooning and indecent exposure laws.
No Ifs, Ands, or Butts
Most indecent exposure laws, like California's for instance, require intent by the exposing party to sexually arouse, or sexually insult or offend. The Golden State statute broadly makes it a crime to willfully expose your genitals to someone else, motivated by a desire to sexually gratify yourself or offend or insult the other person. So if you're not trying to offend or insult someone with your bared buttocks, you're probably alright.
Even if you are trying to get a rise out of someone, the law also only applies to exposing one's genitals. Most courts have ruled that showing a bare female breast is not considered exposing your genitals, thus protecting breastfeeding mothers from prosecution on indecent exposure charges. So as long as you're showing your butt, and only your butt, it generally will not constitute indecent exposure under most indecent exposure statutes, including California's.
Cheeky Free Speech
In 2006, a Maryland court similarly determined that indecent exposure relates only to exposure of the genitals, noting that even if mooning is a "disgusting" and "demeaning" act, it was not illegal. "If exposure of half of the buttocks constituted indecent exposure," the court held, "any woman wearing a thong at the beach at Ocean City would be guilty."
The Maryland court also held that mooning is a form of speech, protected by the First Amendment. Relying on a 1983 case where a woman was arrested for wearing nothing but a cardboard sign that only covered the front of her body during a protest in front of the U.S. Supreme Court, the court ruled the man could not be guilty of indecent exposure, even if the mooning took place in front of a mother and her 8-year-old daughter.