What is the test for an accomplice in a criminal case?

"When there is sufficient evidence that a witness is an accomplice, the trial court is required on its own motion to instruct the jury on the principles governing the law of accomplices." (People v. Frye (1998) 18 Cal.4th 894, 965-966.) "An accomplice is . . . one who is liable to prosecution for the identical offense charged against the defendant on trial in the cause in which the testimony of the accomplice is given." (Pen. Code, 1111.)

"Under California law, a person who aids and abets the commission of a crime is a `principal' in the crime, and thus shares the guilt of the actual perpetrator." (People v. Prettyman (1996) 14 Cal.4th 248, 259.) "[A]n aider and abettor is a person 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.'" (Ibid.)