Adultery is a common reason for couples to divorce. However, since the inception of no-fault divorce, most individuals don't choose to try to prove in court that their spouse has been unfaithful. This makes it less costly and time consuming to obtain a divorce. Adultery is one of the grounds for a fault divorce in states that offer that option. Although laws making adultery illegal are no longer enforced in the U.S. (outside of the military), many states still have them on the books. In the case of fault divorce or when there is a prenuptial agreement in place, adultery can have a serious impact on the outcome of court proceedings. For example, a prenup may contain a clause granting the spouse who was cheated on a greater portion of assets in the divorce. Adultery must generally be proven in these cases. Couples may use such methods as hiring a private investigator to find reliable evidence that is admissible in court.