California Code, Penal Code - PEN § 4001.1

(a) No law enforcement or correctional official shall give, offer, or promise to give any monetary payment in excess of fifty dollars ($50) in return for an in-custody informant's testimony in any criminal proceeding.  Nothing contained herein shall prohibit payments incidental to the informant's testimony such as expenses incurred for witness or immediate family relocation, lodging, housing, meals, phone calls, travel, or witness fees authorized by law, provided those payments are supported by appropriate documentation demonstrating that the money was used for the purposes for which it was given.

(b) No law enforcement agency and no in-custody informant acting as an agent for the agency, may take some action, beyond merely listening to statements of a defendant, that is deliberately designed to elicit incriminating remarks.

(c) As used in this section, an “in-custody informant” means a person described in subdivision (a) of Section 1127a.