The issue of adultery arises in many divorce cases. Sometimes, there has been a history of adulterous relationships by one or both spouses, that has been tolerated over time. Sometimes it is the single coup de gras that, when discovered, becomes the death knell of the marriage. It is estimated that in the United States somewhere between 30%-60% of spouses will engage in infidelity at some point during their marriage. Research consistently shows that 2%-3% of children born in the US are the product of infidelity.Legally, the impact of adultery on a divorce case varies from state to state. For example, in Illinois, the existence of an extramarital affair or affairs affects the outcome of a divorce if the adulterous spouse dissipated funds on his or her paramour(s) or if the adulterous party has infected the other party with a sexually transmitted disease that has disabled that person to the point of diminishing his or her ability to earn an income. (Infecting one’s spouse with a sexually transmitted disease can also give rise to a personal injury action in tort.) It is unlikely to affect a custody determination as long as the children have not been exposed to inappropriate people or situations as a result of the affair.However, in states where fault still factors in divorce proceedings, an extramarital relationship can seriously reduce (or even eliminate) the obligation of one spouse to pay alimony to the unfaithful spouse regardless of need. In some states, such as North Carolina, the first factor for consideration under the alimony statute is marital misconduct, which includes adultery. In other words, an extramarital affair can invoke a financial penalty for the straying spouse.Perhaps the biggest impact of an adulterous relationship is the difficulty it presents in settling a case. More than 90% of dissolution cases end in settlement. Infidelity can bring with it highly charged emotions that complicate settlement negotiations. The non-cheating spouse will usually have a high degree of hurt, anger and humility and a need for retribution. The adulterous spouse may feel guilty and sheepish but may also feel justified in his or her conduct. In either case, reaching settlement on financial matters is complicated when parties have emotional goals. Even worse, reaching agreement in matters of custody and visitation may be exceedingly difficult where the best interests of the children should come first and foremost.Parties considering divorce should seek advice of competent counsel before confronting their spouses about infidelity or suspected infidelity. Information tends to reduce anxiety and understanding the delicate interweaving of the law into this most personal area of marriage can help to assuage concerns and to understand how to proceed forward for the best possible legal outcome.