705 ILCS 305/10
In other than single county circuits, the clerk of the court shall, within 5 days after such drawing, issue summons for a sufficient number of petit jurors, not less than 30 of the persons so drawn, giving their residences and commanding them, to appear at the place of holding such court, at the hour of 10:00 a. m. of such day as the judge shall direct, and a like number to appear at the same place and hour 2 weeks after the time at which the former number of jurors were summoned to appear, and the same number for each 2 weeks thereafter the court will probably be in session, which summons shall be served before the sitting of the court by the issuing clerk as provided in this Section.
The issuing clerk may use first class mail as the initial form of summons, incorporating any reasonable form of request for acknowledgement which is deemed practical and which would provide a reliable proof of service. One permissible method is the use of a duplex card properly addressed to the person summoned to be a juror and requesting the person so summoned to detach and return to the issuing clerk the part of the duplex card which is attached for his acknowledgement with his signature thereon. As used in this Section, a "duplex card" means any postcard with 2 mailable parts with a summons on one part and a detachable acknowledgement of receipt of such summons on the other part.
The issuing clerk may use certified mail as the initial means of service or as a secondary means of service in case the acknowledgement requested in a summons delivered by first class mail is not returned in the time period required. The certified mail may or may not be marked for delivery to the addressee only. If the person summoned to be a juror does not return the acknowledgement of the summons in the time period requested, such prospective juror shall not be deemed guilty of contempt of court.
The certificate of the issuing clerk that he has sent the summons in pursuance of this Section is evidence that he has done so. If service of summons cannot be made by the type of mail service selected, the issuing clerk, shall re-issue such summons that has been returned undelivered and deliver it to the sheriff of the county wherein the court is to be held and he shall make service and return thereof to such issuing clerk of the court.
705 ILCS 305/10