What is the test for direct aiding and abetting in a murder case?

[Citations.] "[I]t is the jury, not the appellate court which must be convinced of the defendant's guilt beyond a reasonable doubt." [Citation.] "In a case, such as the present one, based upon circumstantial evidence, we must decide whether the circumstances reasonably justify the findings of the trier of fact, but our opinion that the circumstances also might reasonably be reconciled with a contrary finding would not warrant reversal of the judgment."'" (People v. Foster (2010) 50 Cal.4th 1301, 1348.)

August was tried for murder under a direct aiding and abetting theory. An aider and abettor is someone who, "'acting with (1) knowledge of the unlawful purpose of the perpetrator; and (2) the intent or purpose of committing, encouraging, or facilitating the commission of the offense, (3) by act or advice aids, promotes, encourages or instigates, the commission of the crime.'" (People v. Prettyman (1996) 14 Cal.4th 248, 259.) While neither presence at the crime scene nor knowledge of the crime and failing to prevent it is sufficient to establish aiding and abetting, factors that may be considered include presence at the crime scene, companionship, and conduct before and after the offense. (People v. Campbell (1994) 25 Cal.App.4th 402, 409.) Moreover, an aider and abettor can be one who is present "'to take charge of an automobile and to keep the engine running, or to drive the "getaway" car and to give direct aid to others in making their escape from the scene of the crime.'" (People v. Swanson-Birabent (2003) 114 Cal.App.4th 733, 744.)