What is the test for determining the guilt of an aider and abettor in a murder case?

In People v. McCoy (2001) 25 Cal.4th 1111, 1122, the court concluded: "[W]hen a person, with the mental state for an aider and abettor, helps or induces another to kill, that person's guilt is determined by the combined acts of all the participants as well as that person's own mens rea. If that person's mens rea is more culpable than another's, that person's guilt may be greater even if the other might be deemed the actual perpetrator." The court also noted: "Absent some circumstance negating malice one cannot knowingly and intentionally help another commit an unlawful killing without acting with malice." (Id. at p. 1123.)

Subsequently, in People v. Samaniego (2009) 172 Cal.App.4th 1148, 1164-1165, the court reasoned: "Though McCoy concluded that an aider and abettor could be guilty of a greater offense than the direct perpetrator, its reasoning leads inexorably to the

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