California Code, Penal Code - PEN § 1111.5

(a) A jury or judge may not convict a defendant, find a special circumstance true, or use a fact in aggravation based on the uncorroborated testimony of an in-custody informant. The testimony of an in-custody informant shall be corroborated by other evidence that connects the defendant with the commission of the offense, the special circumstance, or the evidence offered in aggravation to which the in-custody informant testifies. Corroboration is not sufficient if it merely shows the commission of the offense or the special circumstance or the circumstance in aggravation. Corroboration of an in-custody informant shall not be provided by the testimony of another in-custody informant unless the party calling the in-custody informant as a witness establishes by a preponderance of the evidence that the in-custody informant has not communicated with another in-custody informant on the subject of the testimony.

(b) As used in this section, “in-custody informant” means a person, other than a codefendant, percipient witness, accomplice, or coconspirator, whose testimony is based on statements allegedly made by the defendant while both the defendant and the informant were held within a city or county jail, state penal institution, or correctional institution. Nothing in this section limits or changes the requirements for corroboration of accomplice testimony pursuant to Section 1111.