A person who is legally accountable for the conduct of another which is an element of an offense may be convicted upon proof that the offense was committed and that he was so accountable, although the other person claimed to have committed the offense, has not been prosecuted or convicted, or has been convicted of a different offense or degree of offense, or is not amenable to justice, or has been acquitted.
(ILCS Ch. 720, Act 5, § 5-3)