California Code, Government Code - GOV § 25303

The board of supervisors shall supervise the official conduct of all county officers, and officers of all districts and other subdivisions of the county, and particularly insofar as the functions and duties of such county officers and officers of all districts and subdivisions of the county relate to the assessing, collecting, safekeeping, management, or disbursement of public funds. It shall see that they faithfully perform their duties, direct prosecutions for delinquencies, and when necessary, require them to renew their official bond, make reports and present their books and accounts for inspection.

This section shall not be construed to affect the independent and constitutionally and statutorily designated investigative and prosecutorial functions of the sheriff and district attorney of a county. The board of supervisors shall not obstruct the investigative function of the sheriff of the county nor shall it obstruct the investigative and prosecutorial function of the district attorney of a county.

Nothing contained herein shall be construed to limit the budgetary authority of the board of supervisors over the district attorney or sheriff.