What is the test for a defendant to prove he or she was a "aider and abettor" of a crime?

proof of aider and abettor liability requires proof in three distinct areas: (a) the direct perpetrator's actus reus a crime committed by the direct perpetrator, (b) the aider and abettor's mens rea knowledge of the direct perpetrator's unlawful intent and an intent to assist in achieving those unlawful ends, and (c) the aider and abettor's actus reus conduct by the aider and abettor that in fact assists the achievement of the crime. [Citation.]" (People v. Perez (2005) 35 Cal.4th 1219, 1225.)