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

An aider and abettor's guilt is determined "by the combined acts of all the participants" and by the aider and abettor's own mens rea. (People v. McCoy, supra, 25 Cal.4th at p. 1122.) If the aider and abettor's mens rea is more culpable than the direct perpetrator's, then the aider and abettor's guilt may be greater than the actual perpetrator's. (Ibid.) If the aider and abettor has a less culpable mental state, then the aider and abettor's guilt may be less than that of the actual perpetrator. (People v. Nero (2010) 181 Cal.App.4th 504 [jury could find aider and abettor guilty of manslaughter but find direct perpetrator guilty of second degree murder].) Therefore, to determine each participant's culpability, a jury must evaluate each participant's separate mens rea.