Most states now recognize "no fault" divorce and allow a spouse to file because of "irreconcilable differences." However, many states, including Illinois, still have fault divorce, in which a spouse must establish the grounds for divorce. Having grounds means one spouse is at fault for the marriage's collapse.
An Illinois court will only hear a divorce proceeding if at least one spouse meets the state's residency requirement. Under 750 Illinois Compiled Statutes Chapter 5, Section 401 (750 ILCS 5/401), one spouse must maintain a residence or be stationed with the military in Illinois for at least 90 days prior to filing.
750 ILCS 5/401 sets forth the twelve fault grounds for divorce, including one spouse's impotency, adultery, abuse and bigamy. Abandonment is another ground for divorce recognized in Illinois. Abandonment, also called desertion, occurs when one spouse voluntarily leaves the marital residence for one consecutive year, with no intention of returning.
Illinois law does protect an innocent spouse. If the spouse is locked out of the marital residence against her will, she can successfully defend against a claim that she abandoned/deserted the filing spouse. Additionally, a spouse who is forced out of the marital residence because of the other spouse's behavior, including abuse or habitual alcohol and drug use, cannot be labeled a deserter. Such provocation eliminates the state's requirement that the spouses abandonment be voluntary. However, that spouse may be able to file for divorce under other fault grounds based on the other spouse's conduct.
Generally, grounds do not affect any outstanding issues of the marriage and are merely the reason a court will grant a divorce. However, in some cases, the court will consider the spouse's fault in ending the marriage, including if that spouse abandoneds his family. Under 750 ILCS 5/602, child custody is determined according to what is in the "best interests of the child." This means that if the parent is a deserter, and has not spent a lot of time with his child during the year that he abandoned the marital residence, it is unlikely that a court will grant him sole or even joint custody. However, he will still have the right to visitation with his child.