As used in this chapter, "prisoner" includes an inmate of a prison, jail, or penal or correctional facility. For the purposes of this chapter, a lawfully arrested person who is brought into a law enforcement facility for the purpose of being booked, as described in Section 7 of the Penal Code, becomes a prisoner, as a matter of law, upon his or her initial entry into a prison, jail, or penal or correctional facility, pursuant to penal processes.
Ca. Gov. Code § 844