Notwithstanding any other provision of law, in any prosecution for a conspiracy to violate this Article, no person may be convicted of that conspiracy unless an overt act in furtherance of the agreement is alleged and proved to have been committed by him, her, or by a coconspirator, but the commission of the overt act need not itself constitute predicate activity underlying the specific violation of this Article.
720 ILCS 5/33G-4