Failure to prevent a crime is not enough to make a person an aider and mere knowledge that another is going to commit a crime is not enough to make a person an aider. “Neither his mere presence at the scene of the crime nor his failure, through fear, to prevent a crime establishes, without more, that an accused was an abettor.” (People v. Boyd (1990) 222 Cal. App. 3d 541, 556-557.) “Thus, we conclude that the weight of authority and sound law require proof than an aider and abettor 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.” (People v. Berman (1984) 35 Cal. 3d 547, 560.)
Thus, the jury must be told: preferably by instruction, but by argument if necessary–that:
(1) Failure to prevent a crime does not establish, without more, that the defendant is an aider and abettor.
(2) Mere knowledge of the purpose of the perpetrator does not establish that the defendant is an aider and abettor.