In McCuin v. State, 505 S.W.2d 827 (Tex. Crim. App. 1974), the following standard was articulated concerning when an instruction on the law of parties should be submitted to the jury: Where the evidence introduced upon the trial of the cause shows the active participation in the offense by two or more persons, the trial court should first remove from consideration the acts and conduct of the non-defendant actor. Then, if the evidence of the conduct of the defendant then on trial would be sufficient, in and of itself, to sustain the conviction, no submission of the law of principals [now, parties] is required. On the other hand, if the evidence introduced upon the trial of the cause shows, or raises an issue, that the conduct of the defendant then upon trial is not sufficient, in and of itself, to sustain a conviction, the State's case rests upon the law of principals [parties] and is dependent, at least in part, upon the conduct of another. In such a case, the law of principals [parties] must be submitted and made applicable to the facts of the case. Id. at 830.