Legal Definition of Adultery in Illinois
The Illinois Marriage and Dissolution of Marriage Act does not provide a statutory definition of adultery, nor do any published cases attempt to define the word. Adultery is a common law doctrine and, as such, is generally defined by custom rather than statute or case law.
Although not a lot can be found in the way of written statutory law regarding adultery in Illinois and the consequences one faces for having committed adultery, it is still necessary to have a basic understanding of when adultery occurs.
As a general rule , a person commits adultery in Illinois when he or she engages in sexual relations with someone who is not his or her lawfully wedded spouse and is not in the process of obtaining a divorce. This definition typically is set in Illinois case law, and specifically covers the definition of adultery with a person other than a person’s spouse after a marriage ceremony.
A key idea behind adultery is that it is the sin or offense committed when a married person has sexual intercourse or commits some other sexual act that is considered to be wrong with someone other than his or her lawful spouse.

Adultery Laws Through The Years
Adultery laws in Illinois have a long and complex history, evolving from a time when adultery was a criminal act to the more contemporary judicial and legislative approaches of the 20th century. The original legal framework for adultery was based on the English common law that preceded American individual states. Under this system, not only was adultery a ground for divorce, but so was lewd behavior in general. The law even categorized various offenses into degrees of severity akin to modern legal terminology of felonies and misdemeanors. The concept of "lewdness" encompassed a wide range of sexual faults, including sodomy, bestiality and just about any other form of sex that fell outside the major rules for sexual conduct as laid out in the Book of Leviticus in the Bible. Leviticus also places prohibitions on relationships with other family members, but incestous relationships have been largely decriminalized due to their rarity and practical difficulties in proving them. While the moral and spiritual underpinnings of these laws on adultery remained firmly rooted in society, the growth of divorce law in the 18th and 19th centuries meant that people who sought to dissolve their marriages with the help of the courts started to abandon the idea that a marriage ought to be sustained by criminal means. Adultery remains a major cause for both divorces and separations, which are considered one and the same under the law, but the larger influence of no-fault divorce laws in Illinois means that adultery does not need to be proved in order to end a marriage. Even so, adultery remains an important matter to cover in a divorce proceeding, as it can have a significant impact on a divorce judgment according to how the court decides to interpret irretrievable differences in a marriage. Evidence of someone’s adultery can greatly influence alimony awards and decisions regarding the allocation of assets in a divorce.
Present Day Adultery Laws
Adultery is a word that has fallen out of popularity in the law, and even in usage really. It seems more and more common for people to simply refer to their spouse as their partner and avoid traditional words such as husband or wife. In the law the biggest implication of adultery is no longer in the criminal realm. While Illinois still has a law against adultery, it is rarely prosecuted or enforced. In cases where sister states do still enforce the law you may see an offense such as adultery be used as a justification for a cause of divorce. Where it was once a defense to a divorce, adultery has become an irrelevant factor in the granting of a divorce or annulment.
The only remaining civil implications are in family law. Back in the day, going way back to our grandparents and beyond, many women who were left with kids and limited means by virtue of an unfaithful spouse were left in a terrible position. At some point, courts realized that they could offset the impact that stigma had on these women’s lives by allowing for recovery in divorce cases against the cheating spouse.
To this day, in a very limited number of circumstances (the law is becoming anachronistic to the point of irrelevance in most divorce cases) adultery can have financial implications in your divorce. For courts to consider adultery significant when dividing up assets, you would have to demonstrate that you were negatively impacted by the conduct and that the cheating spouse should not be vindicated by a windfall to him. That might mean that you were given no warning and all of your shared income was spent or that there is some other factual scenario that requires a court to do the right thing by providing you the larger share of assets. Also, there is an adultery statute that applies to spouses who have proven their adultery by a preponderance of the evidence. It says that if one spouse has proven by that same standard that the other committed adultery, they can be awarded up to 50% of marital assets. We are not aware of anyone ever having been awarded that kind of money in Illinois due to an adultery finding, though.
If you have experienced separation or divorce due to your spouse’s infidelity, it is important to speak with an attorney dedicated to protecting your rights. To learn more about adultery in Illinois law and how it impacts your rights, contact us today. We will help you explore your options.
The Impact of Adultery on Divorce
Adultery, often known as "the elephant in the room," in a divorce proceeding can lead one to believe that adultery matters and plays a role in divorce proceedings in Illinois. In the contemporary world of divorce in Illinois, adultery does not matter and does not play a role in the process; however, infidelity can at times have an indirect effect on the issues of alimony, child custody and property division.
When an Illinois divorce proceeding involves infidelity, either party may seek a protective order if the other party is "alienating the affection" of a child by allowing adulterous contact in the presence of the child or by enticing the child to engage in misconduct. Alternatively, a party seeking a protective order must show that the other party has engaged in "lewd" behavior in the presence of the other party or the child.
Illinois is a no-fault state in which divorce proceedings are based upon irreconcilable differences. A finding of adultery is not required. Adultery only arises during a divorce proceeding to the extent it may have an indirect effect upon matters of alimony, child custody or property division.
For instance, a court in Illinois will not reduce alimony simply because a spouse engaged in an extramarital affair. However, a court may reduce or eliminate alimony should it find that the person receiving alimony cohabitated with another person and utilized the alimony payments to support the cohabitational relationship.
As often indicated in Illinois divorce proceedings, the best interests of a child are the controlling factor. The findings of fact with regard to the best interests will not be supported by adultery on the part of a spouse. However, once again, adultery can have an indirect effect on child custody matters should a parent expose a child to inappropriate behavior. For instance, should one parent reveal to a child the other parent’s adultery and that the other parent granted permission to engage in the act, exposing the child to the act and endorsing the act, the court may find that it is not in the best interest of the child to spend time with the parent who is endorsing the act.
Illinois offers equitable distribution of marital property, which is a 50/50 distribution of assets acquired during the marriage and dividing the assets fairly based upon the specifics of the case. Adultery is not a stated factor in the distribution of property pursuant to the Illinois Marriage and Dissolution of Marriage Act. Evidence of adultery, however, may reveal to the court whether either party brought assets into the marriage prior to the date of the marriage. In the instance such evidence is revealed, the non-adulterating party would successfully argue to the court that any relinquishment of alimony payments, which can be owed to the adulterating spouse, would be inappropriate because the other spouse committed a crime which may have assisted him or her in obtaining the matrimonial estate.
Adultery may have an indirect effect on an Illinois divorce proceeding; however, infidelity does not hold the same, dominating presence in the dissolution process of a marriage in Illinois.
Public and Legal Views on Adultery
The public perception of adultery in Illinois, and indeed across the United States, has evolved with societal norms. Once viewed as a moral failing, adultery is currently seen more as a personal choice that may be justified by circumstances. Surveys reveal that contemporary Americans are less likely to consider religious teachings as important in their evaluation of personal moral conduct. The causes are several: secularization, educational advances, the growth of the feminist movement and an influx of immigrant populations with often vastly different worldviews. Public perception often drives legal regulations. However, the law is pragmatic by definition, and when society accepts or tolerates certain behavior, the legal system rarely reflects a contrary position . While not codified in Illinois law, a survey of state court divorce decrees over decades reveals that cases supported by extrinsic evidence of adultery have been in the single digits. Given the lenient treatment of no-fault divorce, it is increasingly difficult for an attorney to prove a case of adultery, even when there is significant evidence related to other facts. In addition, adultery can, in extreme circumstances, affect the outcome of a child custody case. The court would only consider a finding of adultery if the behavior caused the failure of the marriage, and the behavior resulted in a reduction of parental involvement for one of the parties.
Adultery Online
As a consequence of the progressive use of electronic devices, the question has arisen of whether digital affairs are immoral and consequently may be entered as mitigating evidence. These devices include social media websites, such as Facebook, Instagram, Twitter and email, along with cellphone applications that can be used for such things as sending text messages and manipulating photographs of people involved in an affair, for purposes of sending them to another party involved in the affair.
In the case of Lawrence v. 333 S. Wabash Venture LLC, 2019 IL App (1st) 180481, wife attempted to enter into evidence the fact that husband had an affair with a tattoo model which even included nude photographs of the model that husband manipulated and used the images on his Facebook page. The circuit court ruled that the matter was irrelevant and it was excluded as evidence of adultery.
In the case of In re Marriage of Swanson, 2015 IL App (2d) 150035, a digital affair resulted in a divorce. However, the judge ruled that the husband in this case committed adultery only in the sense of exercise of extreme bad judgment, falling short of adultery. The Illinois rules of Evidence Rule 401 define adultery as "relevant evidence means evidence having any tendency to make the existence of any fact that is of consequence to the determination of the action more or less probable than it would be without the evidence." Given this definition, the Swanson judge concluded that, by definition, Shari’s activities fell short of adultery.
According to the Center for Disease Control and Prevention (CDC), a recent study conducted by the National Center for Health Statistics found that about 15 to 20 percent of women and 25 to 33 percent of men among the 15 to 44 age group reported ever having had sexual intercourse with someone other than their spouse or partner,
This goes beyond Facebook to perhaps cover such sites as Tinder or Ashley Madison, which are online dating services that advertise anonymity and confidentiality, and although are marketed for people looking for extramarital affairs, have been proven otherwise.
In light of the fact that an increasing majority of couples are meeting through online means, one could argue the issue of adultery has changed due to this modern technology.
Seeking Legal Help
Consulting legal assistance is a necessary step if you anticipate being involved in any legal proceedings due to allegations of adultery. This is especially the case if you are dealing with divorce proceedings where lost property and assets are a likely outcome, should your spouse be able to prove adultery on your part. An experienced Illinois family law attorney can help you determine what steps are available to you and how best to keep your divorce proceedings fair and equitable for both parties.
A family attorney can draw upon a wealth of experience to provide you with the best options in circumstances where your future could be affected by a ruling that involves missing assets. For example, the court may require you to give some or all of your spouse’s property back if it determines that you committed a form of adultery by concealing an asset . Additionally, if you have children, each of these affairs puts your children in a vulnerable position, and an attorney may be able to help you resolve matters amicably and protect your children in the process.
In any event, the importance of legal representation cannot be overstated. Circumstances exist in which you could be accused of adultery, even if you did not cheat on your spouse. For example, if your spouse has a history of alcohol or drug abuse, engaging in extramarital activity may be an example of adultery, depending on the circumstances.
A family law attorney can carefully review the details of your situation to ensure that everything is thoroughly documented and to offer the best possible advice to you moving forward. Dealing with the loss of a relationship can be difficult, but having sound legal counsel can help ease the financial and legal implications so that you can move into a new chapter of your life.