California Code, Penal Code - PEN § 13154

Each reporting agency shall report to the Department of Justice each arrest for the commission of a public offense while in custody in any local detention facility, or any state prison, as provided in Chapter 4 (commencing with Section 653.75) of Title 15, for inclusion in that person's state summary criminal history record. The report shall include the public offense committed and a reference indicating that the offense occurred while the person was in custody in a local detention facility or state prison.