Adultery Laws in Illinois

By Claire Gillespie

Updated July 20, 2018

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If you're wondering in which states is adultery a crime, the answer is, in several of them. Cheating on your spouse is still illegal in several states, including Arizona, Florida, Kansas, Idaho and Illinois. A person found guilty of adultery in Illinois could, in theory, face a particularly harsh punishment of up to a year in jail for both the cheating spouse and the person he cheated with.

Illinois Adultery Statutes

Adultery is defined under Illinois criminal law as when a person has sexual intercourse with another not his or her spouse, if the behavior is open and notorious. This means the act of adultery is known by members of the public, the adulterer's spouse or any other person. The adulterer may be married and know that the person he is having sexual intercourse with is not his spouse, or unmarried but know that the person he is having sexual intercourse with is married. In other words, it doesn't matter which party is married for someone to be found guilty of adultery.

Consequences of Adultery in Illinois

Adultery is a Class A misdemeanor in Illinois. A Class A misdemeanor is punishable by a fine not exceeding $2,500 for each offense and/or a sentence of conditional discharge, probation, periodic imprisonment or imprisonment of up to one year. However, whether the law against adultery is regularly enforced or not is another matter.

Adultery and Divorce in Illinois

At one time, Illinois divorce laws recognized fault grounds for divorce, including adultery. Other fault grounds were bigamy, habitual drunkenness and mental or physical cruelty. But following extensive changes to the Illinois Marriage and Dissolution of Marriage Act, Illinois elimated all fault grounds for divorce and became a no-fault divorce state on January 1, 2016.

This means you only need to show irreconcilable differences to get a divorce in Illinois. The irreconcilable differences must have caused the irretrievable breakdown of the marriage, and any attempts at reconciliation must have failed or would be impracticable and not in the best interests of the family. Parties must also show that they have been living separate and apart for at least six months immediately before divorce proceedings are instigated.

While one spouse's adultery may well have contributed to the irretrievable breakdown of the marriage, adultery alone cannot be used as a grounds for divorce in Illinois.