Adultery is consensual sexual intercourse between a married person and someone other than that person’s spouse. Adultery is rarely charged as a crime. It is more often a concern as a part of a divorce case.
Adultery is one of many possible grounds for divorce in the majority of states in the United States. Historically, adultery was one of the few grounds, and in one state the only reason, on which divorce would be allowed. Adultery was also historically important in states that linked child custody or property decisions to the grounds for divorce. Now that most states have “no fault” grounds for divorce, adultery is much less legally significant. Some states even have a requirement that the grounds for divorce not be taken into account when the judge decides issues of child custody and property distribution.
Proving adultery can be very difficult because sexual acts rarely take place in front of witnesses. Some courts have considered adultery proven when the parties had motivation and opportunity, such as checking in to a motel together, to engage in sexual conduct. A few courts have even been called upon to determine whether graphic sexual communication over the Internet constitutes adultery, but there is no clear law yet established.