Cal. Gov. Code § 1029.1

The Department of Corrections and the Department of the Youth Authority shall complete a background investigation, using as guidelines standards defined by the Commission on Peace Officer Standards and Training, of any applicant for employment as a peace officer before the applicant may be employed or begin training as a peace officer. In order to reduce potential duplication of effort by individual institutions, investigations shall be accomplished by each department on a centralized or regional basis to the extent administratively feasible.