Does the doctrine of the lesser included offense doctrine apply to a defendant who has pleaded guilty to a charge of a related but not necessarily included crime?

While we conclude that fairness to the defendant requires that the defendant receive instructions on related but not necessarily included offenses, we emphasize that the benefit of such instructions does not run only to the defendant. (People v. Marshall, supra, 48 Cal.2d 394, 405, 309 P.2d 456.) Just as the lesser included offense doctrine serves the interests of the People by permitting conviction of a lesser offense rather than acquittal of a clearly guilty defendant when the prosecution fails to prove the charged offense, instructions on related offenses will ensure that some guilty defendants who would otherwise go free will be punished for a crime which they committed even though it was overlooked by a prosecutor or was not charged because the prosecutor overestimated the strength of the People's evidence.