(a) A person is legally accountable for the behavior of another if, acting with the culpable mental state sufficient for the commission of the offense in question, he causes an innocent person to engage in such behavior.
(b) As used in this section, an "innocent person" includes any person who is not guilty of the offense in question, despite his behavior, because of:
(1) Criminal irresponsibility or other legal incapacity or exemption.
(2) Unawareness of the criminal nature of the conduct in question or of the defendant's criminal purpose.
(3) Any other factor precluding the mental state sufficient for the commission of the offense in question.