What is the test for aiding and abetting a crime?

"[U]nder the general principles of aiding and abetting, 'an aider and abettor [must] act with knowledge of the criminal purpose of the perpetrator and with an intent or purpose either of committing, or of encouraging or facilitating commission of, the offense.' [Citation.]" (People v. Prettyman (1996) 14 Cal.4th 248, 262.) Here, the jury was instructed accordingly: "Someone aids and abets a crime if he knows of the perpetrator's unlawful purpose and he specifically intends to and does, in fact, aid, facilitate, promote, encourage, or instigate the perpetrator's commission of that crime."

An aider and abettor is guilty not only of the specific crime he aids and abets, but also "for any other offense that was a 'natural and probable consequence' of the crime aided and abetted. [Citation.]" (People v. Prettyman, supra, 14 Cal.4th at p. 260.) "A person who knowingly aids and abets criminal conduct is guilty of not only the intended crime but also of any other crime the perpetrator actually commits that is a natural and probable consequence of the intended crime. The latter question is not whether the aider and abettor actually foresaw the additional crime, but whether, judged objectively, it was reasonably foreseeable. [Citation.]" (People v. Mendoza (1998) 18 Cal.4th 1114, 1133.)

The murder of a rival gang member during a gang-related fight has been held to be a natural and probable consequence of the gang fight. (People v. Medina (2009) 46 Cal.4th 913, 921-922 and cases cited.)

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