A person is legally accountable for the conduct of another when:
   (A)   Having a mental state described by the statute defining the offense, he or she causes another to perform the conduct, and the other person in fact or by reason of legal incapacity lacks such a mental state;
   (B)   The section defining the offense makes him or her so accountable; or
   (C)   Either before or during the commission of an offense, and with the intent to promote or facilitate that commission, he or she solicits, aids, abets, agrees, or attempts to aid, that other person in the planning or commission of the offense.  When two or more persons engage in a common criminal design or agreement, any acts in the furtherance of that common design committed by one party are considered to be the act of all parties to the common design or agreement and all are equally responsible for the consequences of those further acts.  Mere presence at the scene of a crime does not render a person accountable for an offense; a person's presence at the scene of the crime, however, may be considered with other circumstances by the trier of fact when determining accountability. A person is not so accountable, however, unless the section defining the offense provides otherwise, if:
      (1)   He or she is victim of the offense committed; or
      (2)   The offense is so defined that his or her conduct was inevitably incident to its commission; or
      (3)   Before the commission of the offense, he or she terminates his or her effort to promote or facilitate that commission, and does one of the following:  (i) wholly deprives his or her prior efforts of effectiveness in that commission, (ii) gives timely warning to the proper law enforcement authorities, or (iii) otherwise makes proper effort to prevent the commission of the offense.
(ILCS Ch. 720, Act 5, § 5-2)  ('64 Code, § 22-l)
Statutory reference:
   Accountability of corporations and agents of corporations, ILCS Ch. 720, Act 5, §§ 5-3 through 5-5
   Criminal responsibility, ILCS Ch. 720, Act 5, §§ 6-1 through 6-4