What is the test for the natural and probable consequences doctrine in the context of second degree murder?

(People v. Chiu (2014) 59 Cal.4th 155, 158-159.) "In the context of murder, the natural and probable consequences doctrine serves the legitimate public policy concern of deterring aiders and abettors from aiding or encouraging the commission of offenses that would naturally, probably, and foreseeably result in an unlawful killing. A primary rationale for punishing such aiders and abettorsto deter them from aiding or encouraging the commission of offensesis served by holding them culpable for the perpetrator's commission of the nontarget offense of second degree murder." (Id. at p. 165.) "[P]unishment for second degree murder is commensurate with a defendant's culpability for aiding and abetting a target crime that would naturally, probably, and foreseeably result in a murder under the natural and probable consequences doctrine." (Id. at p. 166.)