765 ILCS 5/25
Current through Public Act 103-593
If any grantor shall not have duly acknowledged the execution of any deed or instrument entitled to be recorded, and the subscribing witness or witnesses be dead, or not to be had, it may be proved by evidence of the handwriting of the grantor, and of at least one of the subscribing witnesses, which evidence shall consist of the testimony of two or more disinterested persons swearing to each signature.
765 ILCS 5/25