What is the legal test for liability under the "natural and probable consequences" doctrine?

^2. "The natural and probable consequences route to a finding of criminal liability operates as follows: ' "A person who knowingly aids and abets criminal conduct is guilty of not only the intended crime [target offense] but also of any other crime the perpetrator actually commits [nontarget offense] that is a natural and probable consequence of the intended crime. The latter question is not whether the aider and abettor actually foresaw the additional crime, but whether, judged objectively, it was reasonably foreseeable. [Citation.]" [Citation.] Liability under the natural and probable consequences doctrine "is measured by whether a reasonable person in the defendant's position would have or should have known that the charged offense was a reasonably foreseeable consequence of the act aided and abetted." ' [Citation.] In short, natural and probable consequences liability for crimes occurs when the accused did not necessarily intend for the ultimate offense to occur but was at least negligent (from the standard expected of a reasonable person in the accused's position) about the possibility that committing the proximate offense would precipitate the ultimate offense that actually occurred." (People v. Rivas (2013) 214 Cal.App.4th 1410, 1431-1432 (Rivas).)