Illinois Statutes Chapter 705. Courts § 35/4.3. Witness fees

(a) Every witness attending in any county upon trials in the courts, except for actions arising under Article II of the Juvenile Court Act of 1987,  1 shall be entitled to receive the sum of $20 for each day's attendance and $0.20 per mile each way for necessary travel. For attending in a foreign county, each day's travel shall constitute a day of attendance. Every person attending for the purpose of having his deposition taken shall receive the same per diem and mileage as provided in this Section for witnesses in circuit courts. No allowance or charge shall be made, however, for the attendance of a witness unless the witness makes an affidavit stating the number of days he or she actually attended, and that attendance was at the instance of one or both of the parties or his or her attorney.

(b) In a criminal case or action arising under Article II of the Juvenile Court Act of 1987 in which a witness is required to attend from a foreign county or state, either before the grand jury or at the trial of the cause in the court, the witness shall receive the same per diem and mileage as provided in this Section for witnesses in circuit courts to be paid out of the county treasury of the county where the crime was committed or the case under Article II of the Juvenile Court Act of 1987 is filed on the certificate of the clerk of the court where the trial is being had if the witness makes an affidavit stating (i) the distance traveled, (ii) that it was the usually traveled and most direct route, (iii) the number of days' actual travel and attendance, and (iv) that attendance was at the instance of the State's Attorney or the accused, or his or her attorney or, in the case of an action filed under Article II of the Juvenile Court Act of 1987, at the instance of the State's Attorney or attorney of any other party to the action. To the affidavit shall be added the certificate of the judge that the amount is reasonable and that the witness was a material witness in the court or before the grand jury.