Penal Code section 4532 makes it illegal for a prisoner to escape from jail, but not from the custody of an officer while in jail. Appellant was arrested for Penal Code section 69, booked, and detained in a jail cell. When an officer went to retrieve a plastic utensil from appellant’s cell, appellant attempted to push her way out of the cell. The ensuing struggle between officers and appellant lasted 20 to 30 minutes and ended only when appellant was sprayed in the face with a fire extinguisher. Appellant was charged with attempted escape by force or violence and assault. The trial court rejected appellant’s interpretation of Penal Code section 4532, namely, that under the statute it is not illegal to escape from the custody of an officer while in jail, and instructed the jury pursuant to CALJIC No. 731, which permitted the jury to find appellant guilty of attempted escape if it found she attempted to escape from an officer’s custody within the confines of the jail. The appellate court reversed, observing that the legislative history of section 4532, the wording of the statute, and common sense combine to interpret the statute in such a manner that merely breaking away from a custodial officer within the jail does not constitute an escape within the meaning of the statute. Here the error was not harmless as the trial court, over the objection of defense counsel, emphasized in its instructions that escape could be found where the defendant broke away from a custodial officer within the jail.