Can a witness be considered an accomplice in a criminal case?

" 'An accomplice is . . . defined as 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.) If sufficient evidence is presented at trial to justify the conclusion that a witness is an accomplice, the trial court must so instruct the jury, even in the absence of a request. [Citation.] Of course, an accomplice has a natural incentive to minimize his own guilt before the jury and to enlarge that of his cohorts; accordingly, the law requires an accomplice's testimony be viewed with caution to the extent it incriminates others." (People v. Brown (2003) 31 Cal.4th 518, 555.)