Although a spouse's infidelity can be hurtful, his indiscretions usually have no effect on a court's custody decision -- unless the spouse involved the children in the affair in some way. For example, if the cheating spouse brought his paramour around his children or had them lie for him, he may lose custody if the court feels the behavior was contrary to the children's best interests.
Custody Based on Child's Best Interests
Although state laws vary, every state bases custody on the best interests of the child. To make this determination courts evaluate a variety of factors. Common ones include the relationship between the child and each parent, physical and mental health of the parents and child, ability of each parent to provide for the child, child's wishes and whether there is any history of domestic violence.
Adultery and Custody are Separate Issues
Adultery is usually not among the "best interests" factors a court considers when deciding custody. This is because adultery and custody are separate and unrelated issues. In fact, many courts will not consider adultery in a divorce case at all, unless a spouse uses it as grounds for divorce or the spouse used marital assets to support the affair in some way; thus, the court may allocate more property to the innocent spouse. However, if a cheating spouse involved his children in the affair, the court is likely to find the parent acted against his children's best interests. In this rare instance, the parent's adulterous behavior may affect the court's custody decision.