What is the legal test for a person to be convicted of premeditated murder?

the considerations for and against a choice to kill before he or she completes the acts that caused the death. [Citations.]" (People v. Chiu (2014) 59 Cal.4th 155, 166.) "Aiders and abettors may . . . be convicted of first degree premeditated murder based on direct aiding and abetting principles. [Citation.] Under those principles, the prosecution must show that the defendant aided or encouraged the commission of the murder with knowledge of the unlawful purpose of the perpetrator and with the intent or purpose of committing, encouraging, or facilitating its commission. [Citation.] . . . Such an aider and abettor, then, acts with the mens rea required for first degree murder." (Id. at pp. 166-167.)