Penal Code § 1140
CHAPTER 3. Conduct of the Jury After the Cause Is Submitted to Them
Except as provided by law, the jury cannot be discharged after the cause is submitted to them until they have agreed upon their verdict and rendered it in open court, unless by consent of both parties, entered upon the minutes, or unless, at the expiration of such time as the court may deem proper, it satisfactorily appears that there is no reasonable probability that the jury can agree.