What is the legal test for a direct aider and an abettor of a murder?

Under the amendment to section 188, subdivision (a)(3), to be guilty of murder other than as specified in section 189, subdivision (e), concerning felony murder, the subjective mens rea of "malice aforethought" must be proved: "[T]o be convicted of murder, a principal in a crime shall act with malice aforethought." (See also Stats. 2018, ch. 1015, 1, subd. (g) ["[a] person's culpability for murder must be premised upon that person's own actions and subjective mens rea"].) And that required element of malice "shall not be imputed to a person based solely on his or her participation in a crime." ( 188, subd. (a)(3); People v. Lopez (2019) 38 Cal.App.5th 1087, 1103 [review granted Nov. 13, 2019, S258175].)

However, this amendment did not alter the law regarding the criminal liability of active or direct aiders and abettors of murder because such persons necessarily "know and share the murderous intent of the actual perpetrator." (People v. McCoy (2001) 25 Cal.4th 1111, 1118; see People v. Chiu (2014) 59 Cal.4th 155, 167 [a direct aider and

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abettor "acts with the mens rea required for first degree murder"].) To prove liability for murder as a direct aider and abettora theory that is still viable after the amendments"the prosecution must show the defendant acted with knowledge of the perpetrator's criminal purpose and with the intent of committing, encouraging, or facilitating commission of the offense." (People v. Nguyen (2020) 53 Cal.App.5th 1154, 1164.) One who directly aids and abets another who commits murder is thus liable for murder under the new law, just as he or she was liable under the old law.