What is the 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. [Citations.] 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 someone subject to prosecution for the charged crimes by reason of aiding and abetting or being a member of a conspiracy to commit the charged crimes. [Citations.]" (Id. at 1224.)