Evid. Code, § 1042

(a) Except where disclosure is forbidden by an act of the Congress of the United States, if a claim of privilege under this article by the state or a public entity in this state is sustained in a criminal proceeding, the presiding officer shall make such order or finding of fact adverse to the public entity bringing the proceeding as is required by law upon any issue in the proceeding to which the privileged information is material.

(b) Notwithstanding subdivision (a), where a search is made pursuant to a warrant valid on its face, the public entity bringing a criminal proceeding is not required to reveal to the defendant official information or the identity of an informer in order to establish the legality of the search or the admissibility of any evidence obtained as a result of it.

(c) Notwithstanding subdivision (a), in any preliminary hearing, criminal trial, or other criminal proceeding, any otherwise admissible evidence of information communicated to a peace officer by a confidential informant, who is not a material witness to the guilt or innocence of the accused of the offense charged, is admissible on the issue of reasonable cause to make an arrest or search without requiring that the name or identity of the informant be disclosed if the judge or magistrate is satisfied, based upon evidence produced in open court, out of the presence of the jury, that such information was received from a reliable informant and in his discretion does not require such disclosure.

(d) When, in any such criminal proceeding, a party demands disclosure of the identity of the informant on the ground the informant is a material witness on the issue of guilt, the court shall conduct a hearing at which all parties may present evidence on the issue of disclosure. Such hearing shall be conducted outside the presence of the jury, if any. During the hearing, if the privilege provided for in Section 1041 is claimed by a person authorized to do so or if a person who is authorized to claim such privilege refuses to answer any question on the ground that the answer would tend to disclose the identity of the informant, the prosecuting attorney may request that the court hold an in camera hearing. If such a request is made, the court shall hold such a hearing outside the presence of the defendant and his counsel. At the in camera hearing, the prosecution may offer evidence which would tend to disclose or which discloses the identity of the informant to aid the court in its determination whether there is a reasonable possibility that nondisclosure might deprive the defendant of a fair trial. A reporter shall be present at the in camera hearing. Any transcription of the proceedings at the in camera hearing, as well as any physical evidence presented at the hearing, shall be ordered sealed by the court, and only a court may have access to its contents. The court shall not order disclosure, nor strike the testimony of the witness who invokes the privilege, nor dismiss the criminal proceeding, if the party offering the witness refuses to disclose the identity of the informant, unless, based upon the evidence presented at the hearing held in the presence of the defendant and his counsel and the evidence presented at the in camera hearing, the court concludes that there is a reasonable possibility that nondisclosure might deprive the defendant of a fair trial.