Illinois is considered a “no fault” state. This means that the Courts in Illinois will not take a parties’ conduct (or misconduct) into consideration when they decide how the property will be divided. So, if your spouse cheats, that is not going to be a valid reason for a Court to award you more property.
In Illinois, we require “grounds” to get divorced (unless they are stipulated to, which is for another day’s blog). “Grounds” sometimes include adultery. However, this is just the basis for the actual divorce and has nothing to do with how property will be divided.
Illinois is what we call an “equitable division” state. That means that a Court has some discretion when awarding divorcing parties their property. An “equitable division” in one situation might be a 50/50 division. In another case, it could be a 65/35 division of all property. The Court can consider many factors, including, but not limited to: ages of the parties, health of the parties, contribution of the parties during the marriage, dissipation of marital funds of the parties during the marriage, work history, educational background, earning potential, and more, when making an “equitable distribution” of the marital estate. Every scenario is different.
If a spouse spends a significant portion of funds on a significant other after the breakdown of the marriage, the Court might award the other spouse some of those monies back. The Court calls this “Dissipation”. So, if your spouse is flying a new girlfriend or boyfriend to Europe, taking lavish vacations, buying them lavish gifts and spending big sums of money on them, that is likely not for the benefit of the marriage and some of those funds are recoverable. Just generally, since Illinois is a “no fault” state, the Court will not make a determination of who receives what property based upon whether or not they are at fault for the breakdown of the marriage.