For a person to be convicted as a co-perpetrator under section 196A of the Criminal Law (Codification and Reform) Act, the State must prove: (1) that the accused was physically present with the actual perpetrator when the crime was committed; (2) that the accused knowingly associated with the commission of the crime; and (3) that the accused possessed the requisite mens rea, being either intention to commit the crime, knowledge that it would be committed, or realization of a real risk or possibility that such a crime would be committed. The mere supply of an instrumentality (weapon) used to commit a crime, in the absence of evidence establishing consciousness of its intended criminal use and common purpose, is insufficient to establish co-perpetrator liability. Where the evidence permits multiple reasonable inferences, including an innocent explanation, and the State has not excluded reasonable doubt, the accused must be acquitted.