Recall of a criminal sentence PC § 1170
Common Law: Court has no jurisdiction over defendant once execution of sentence commences
Under the common law, once execution of the sentence has commenced or the trial court relinquishes custody over the defendant, the trial court no longer has jurisdiction over a defendant. If trial court retains the actual or constructive custody of the defendant and the execution of sentence has not begun, the court may vacate and modify the sentence. In a criminal case, the execution of a judgment of conviction is the process of carrying the judgment into effect. Under the common law, the court relinquishes control over a defendant by committing and delivering the defendant to the prison authority. However, Pen C § 1170(d), extends the jurisdiction of the trial court to mitigate the sentence imposed by an additional 120 days. People v. Superior Court (Cornelius) (1995), 31 Cal. App. 4th 343.
PC § 1170 (d) and mitigation of sentence