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

"When a jury receives substantial evidence that a witness who has implicated the defendant was an accomplice, a trial court on its own motion must instruct it on the principles regarding accomplice testimony. [Citation.] This includes instructing the jury that an accomplice's testimony implicating the defendant must be viewed with caution and corroborated by other evidence. [Citations.]" (People v. Houston (2012) 54 Cal.4th 1186, 1223.) An accomplice is "one who is liable for prosecution for the identical offense charged against the defendant" as an aider and abettor or as part of a conspiracy. ( 1111, italics added; People v. Houston, supra, at p. 1224.) An accomplice must have guilty knowledge and intent with regard to the commission of the crime. (Ibid.)