The trial court must ensure that a police agency’s claim of privilege for a surveillance location is supported by evidence sufficient to demonstrate that the agency’s need for continued secrecy outweighs that of defendant’s need for disclosure during the course of criminal prosecution. It was alleged that a minor engaged in a drug transaction and possessed drugs. During juvenile court proceedings, counsel for minor attempted to cross-examine the sole witness, a police officer, as to the location from which he had observed the alleged sales transaction. However, the prosecution asserted a claim of privilege as to the location. After an in camera hearing, at which defense counsel and minor were excluded, the court allowed the prosecution to establish the claim and, further, ruled that the location was not material. Held: Reversed. Under Evidence Code section 1040 (privilege for official information), a claim of privilege is allowed if disclosure is against public interests. When the government claims that information is privileged on the basis of public interest, the court must follow the procedure explained in People v. Montgomery (1988) 205 Cal.App.3d 1011, 1021. Here, the trial court did not follow the correct procedure. The minor was not given an opportunity to propose questions for the in camera hearing and the result of the hearing was treated as a final, instead of a preliminary, determination of the privilege issue. Although an in camera hearing was held, the prosecution did not reveal the surveillance location to the court and instead explained in generic terms why police prefer to not reveal such locations. Due to the minimal information revealed, the appellate court concluded that the prosecution failed to sustain its burden of proving that the need for confidentiality of that particular surveillance location outweighed the need for disclosure. As a result, the court abused its discretion in upholding the claim. Even if the claim had been properly sustained, the court also erred in ruling that the location of the police officer was not material. Because there was no significant corroborating evidence as to the officer’s testimony regarding his observations, without the knowledge of the location of surveillance, there was little to demonstrate that these observations were accurate.