How have courts used the aiding and abetting instruction in a murder case?

Respondent relies on People v. Staten (2000) 24 Cal.4th 434 to support the use of aiding and abetting instructions in this case. There the defendant was charged with and convicted of murdering his parents. At trial, over a defense objection, the trial court gave aiding and abetting instruction noting, "`the People's theory is that the defendant was involved; that they have no direct evidence that he was the perpetrator, even though that's also their theory, that (A) he was the perpetrator; (B), if he wasn't, he's an aider and abettor.'" (Id. at p. 457.)