In Illinois you cannot be discrimination against because of arrest record. The fact that you have been arrested can't be used by a company to make a hiring decision on you. Because many companies outsource their background checks and other human resource activity, my Chicago office is seeing an increase in the number of arrest record discrimination cases.
If you have been arrested and thought you were getting a job and suddenly did not get it call my office. However if you were arrested and convicted this won't apply as you can be not hired based on conviction in Illinois.