California Code, Government Code - GOV § 27000.3

(a) With regard to county funds deposited in the county treasury, the board of supervisors is the agent of the county who serves as a fiduciary and is subject to the prudent investor standard, unless a delegation has occurred pursuant to Section 53607 in which case the county treasurer shall be the agent of the county with respect to these funds, serve as a fiduciary, and be subject to the prudent investor standard and the board of supervisors shall not be the agent, serve as a fiduciary, or be subject to the prudent investor standard.

(b) With regard to funds deposited in the county treasury that are deposited by local agencies other than the county and at the discretion of those local agencies, the county treasurer serves as a fiduciary subject to the prudent investor standard.

(c) When investing, reinvesting, purchasing, acquiring, exchanging, selling, or managing public funds, the county treasurer or the board of supervisors, as applicable, shall act with care, skill, prudence, and diligence under the circumstances then prevailing, specifically including, but not limited to, the general economic conditions and the anticipated needs of the county and other depositors, that a prudent person acting in a like capacity and familiarity with those matters would use in the conduct of funds of a like character and with like aims, to safeguard the principal and maintain the liquidity needs of the county and the other depositors. Within the limitations of this section and considering individual investments as part of an overall investment strategy, investments may be acquired as authorized by law. Nothing in this chapter is intended to grant investment authority to any person or governing body except as provided in Sections 53601, 53607, and 53635.