(a) Rule of Privilege. The United States or a state or subdivision thereof has a privilege to refuse to disclose the identity of a person who has furnished information relating to or assisting in an investigation of a possible violation of a law to a law enforcement officer or member of a legislative committee or its staff conducting an investigation.
(b) Who May Claim. The privilege may be claimed by an appropriate representative of the public entity to which the information was furnished.
(1) Voluntary disclosure; informer a witness. No privilege exists under this rule if the identity of the informer or his interest in the subject matter of his communication has been disclosed to those who would have cause to resent the communication by a holder of the privilege or by the informer's own action, or if the informer appears as a witness for the government.
(2) Testimony on relevant issue. If it appears in the case that an informer may be able to give testimony relevant to any issue in a criminal case or to a fair determination of a material issue on the merits in a civil case to which a public entity is a party, and the informed public entity invokes the privilege, the court shall give the public entity an opportunity to show in camera facts relevant to determining whether the informer can, in fact, supply that testimony. The showing will ordinarily be in the form of affidavits, but the court may direct that testimony be taken if it finds that the matter cannot be resolved satisfactorily upon affidavit. If the court finds there is a reasonable probability that the informer can give the testimony, and the public entity elects not to disclose his identity, in criminal cases the court on motion of the defendant or on its own motion shall grant appropriate relief, which may include one or more of the following: requiring the prosecuting attorney to comply, granting the defendant additional time or a continuance, relieving the defendant from making disclosures otherwise required of him, prohibiting the prosecuting attorney from introducing specified evidence, and dismissing charges. In civil cases, the court may make any order the interests of justice require. Evidence submitted to the court shall be sealed and preserved to be made available to the appellate court in the event of an appeal, and the contents shall not otherwise be revealed without consent of the informed public entity. All counsel and parties are permitted to be present at every stage of proceedings under this subdivision except a showing in camera at which no counsel or party shall be permitted to be present.