What is the legal test for "aiding and abetting" a crime?

Because section 31 defines as principals all who directly commit a given offense or who aid and abet in its commission, the same criminal [7 Cal.4th 1039] liability attaches whether a defendant directly perpetrates the offense or aids and abets the perpetrator. People v. Beeman (1984) 35 Cal.3d 547, 554-555, 199 Cal.Rptr. 60, 674 P.2d 1318; People v. Brady (1987) 190 Cal.App.3d 124, 132-133, 235 Cal.Rptr. 248. ⁶ The doctrine in Beeman that one may be liable when he or she aids the perpetrator of an offense, knowing of the perpetrator's unlawful purpose and intending, by his or her act of aid, to commit, encourage, or facilitate commission of the offense, "snares all who intentionally contribute to the accomplishment of a crime in the net of criminal liability defined by the crime, even though the actor does not personally engage in all of the elements of the crime." People v. Brady, supra, 190 Cal.App.3d 124, 132, 235 Cal.Rptr. 248. Because the aider and abettor is subject to the same criminal liability and the same potential punishment as the perpetrator, it is essential to distinguish the act and intent that constitute "aiding and abetting" the commission of a crime, from conduct that will incur the lesser liability of an "accessory" to the crime--defined as conduct by one who, "after a felony has been committed,... aids a principal in such felony, with the intent that said principal may avoid or escape from arrest, trial, conviction or punishment, having knowledge that said principal has committed such felony or has been charged with such felony...." ( 32, italics added.) ⁷

It is settled that if a defendant's liability for an offense is predicated upon the theory that he or she aided and abetted the perpetrator, the defendant's intent to encourage or facilitate the actions of the perpetrator "must be formed prior to or during 'commission' of that offense." People v. Cooper (1991) 53 Cal.3d 1158, 1164, 282 Cal.Rptr. 450, 811 P.2d 742, italics in the original; see People v.

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