Illinois law requires those seeking a divorce to specify a ground for the divorce. The grounds include fault-based grounds and a “no fault” divorce. The fault based grounds for divorce in Illinois include:
Without cause or provocation, the defendant was at the time of the marriage and continues to be naturally impotent;
The defendant had a living spouse at the time of the marriage;
The defendant committed adultery;
The defendant has willfully deserted the spouse for a period of at least one year;
The defendant has been guilty of habitual drunkenness for a period of two years;
The defendant has been guilty of gross and confirmed habits caused by excessive use of addictive drugs for a period of two years;
The defendant has attempted to kill the plaintiff by poison or other means showing malice;
The defendant has been guilty of extreme and repeated physical or mental cruelty;
The defendant has been convicted of a felony or other crime of infamy; or
The defendant has infected the plaintiff with a sexually transmitted disease.
Of course, a divorce can also be granted in Illinois on no fault grounds.