705 ILCS 305/17
After the grand jury is impaneled, it shall be the duty of the court to appoint a foreman, who shall have power to swear or affirm witnesses to testify before them, and whose duty it shall be, when the grand jury, or any nine of them, find a bill of indictment to be supported by good and sufficient evidence, to indorse thereon "A true bill;" where they do not find a bill to be supported by sufficient evidence, to indorse thereon "Not a true bill;" and shall, in either case, sign his name as foreman, at the foot of said endorsement, and shall also, in each case in which a true bill shall be returned into court as aforesaid, note thereon the name or names of the witness or witnesses upon whose evidence the same shall have been found.
705 ILCS 305/17