What is the standard of prejudice for failing to properly instruct a jury in the case of aiding and abetting?

CALJIC No. 3.01 (1980 rev.) as read to the jury provides: "A person aids and abets in the commission of a crime if with knowledge of the unlawful purpose of the perpetrator of the crime, he aids, promotes, encourages or instigates by act or advice the commission of such crime, [p] Mere presence at the scene of a crime which does not in itself assist the commission of the crime does not amount to aiding and abetting. [p] Mere knowledge that a crime is being committed and the failure to prevent it does not amount to aiding and abetting."

5 People v. Watson, supra, 46 Cal.2d 818, 299 P.2d 243.

6 Hearings have been granted in People v. Johnson, 155 Cal.App.3d 241, 201 Cal.Rptr. 908 (hrg. granted July 26, 1984) and other cases. The principle issue presented in these cases concerns the standard of prejudice for failure to properly instruct on the intent required for aiding and abetting.