What is the legal test for an aider and abettor to be convicted of a first-degree premeditated murder?

Outside of the natural and probable consequence doctrine, an aider and abettor's mental state must be at least that required of the direct perpetrator, and when the crime is murder, the aider and abettor must know and share the murderous intent of the actual perpetrator. (People v. McCoy (2001) 25 Cal.4th 1111, 1117-1118; see also, People v. Chiu (2014) 59 Cal.4th 155, 165 [aider and abettor may not be convicted of first-degree premeditated murder under natural and probable consequence doctrine].)