In People v. Wickersham (1982) 32 Cal.3d 307, disapproved on an unrelated point in People v. Barton (1995) 12 Cal.4th 186, 200-201, 906 P.2d 531, the court discussed the area of lesser included offense instructions and when they should and should not be given. The court stated that the trial court must instruct on those principles relevant to the issues related to the case and which are connected to the facts before the court. (Ibid.) However, the court pointed out that a defendant is not entitled to an instruction on a lesser included offense "when there is no evidence that the offense was less than that charged." ( People v. Barton, supra, 32 Cal.3d at pp. 323-324.) In determining when the court is obligated to instruct on a lesser-included offense, the court stated: "This does not require -- or permit -- the trial court to determine the credibility of witnesses. It simply frees the trial court from any obligation to present theories to the jury which the jury could not reasonably find to exist." (Ibid.)