People v. Panizzon, 13 Cal.4th 68, 913 P.2d 1061, 1073-1074 (April 18, 1996) ([a]n appellate court may correct a sentence that is not authorized by law whenever the error comes to the attention of the court); quoting In re Harris (1993) 5 Cal.4th 813, 842, 21 Cal.Rptr.2d 373, 855 P.2d 391).

The court went on to qualify this general statement:

[The] defendant argues that California decisional law has long recognized the necessity of affording judicial review where, as here, a sentence is challenged as invalid or in excess of the court's jurisdiction. We disagree.

Appellate courts have relied upon the principle to which defendant refers in allowing habeas corpus review of a claim or sentencing error amounting to an excess of jurisdiction when a defendant has delayed in raising the issue (e.g., In re Harris, supra, 5 Cal.4th at p. 842, 21 Cal. Rptr. 2d 373, 855 P.2d 391) and in holding that an unauthorized sentence is no bar to the imposition of a proper, even if more severe, judgment thereafter (e.g., People v. Serrato (1973) 9 Cal.3d 753, 764"765, 109 Cal.Rptr. 65, 512 P.2d 289, disapproved on other grounds, People v. Fosselman (1983) 33 Cal.3d 572, 583, fn. 1, 189 Cal.Rptr. 855, 659 P.2d 1144; People v. Massengale (1970) 10 Cal.App.3d 689, 693, 89 Cal.Rptr. 237). These authorities, however, do not support appellate review of a sentence disproportionality claim where, as here, the sentence has been negotiated as part of a plea bargain and is not in excess of the maximum statutory penalty.

Id. at 1073-1074.