(1) The government 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 law to a law enforcement officer or member of a legislative committee or its staff conducting an investigation.

(2) The privilege may be claimed by an appropriate representative of the government, regardless of whether the information was furnished to an officer of the government, or of a state or subdivision thereof. The privilege may be claimed by an appropriate representative of a state or subdivision if the information was furnished to an officer thereof, except that in criminal cases the privilege shall not be allowed if the government objects.

(3)(a) 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.

(b) If it appears from the evidence in the case or from other showing by a party that an informer may be able to give testimony necessary to a fair determination of the issue of guilt or innocence in a criminal case or of a material issue on the merits in a civil case to which the government is a party, and the government invokes the privilege, the judge shall give the government an opportunity to show in camera facts relevant to determining whether the informer can, in fact, supply that testimony. The showing may be in the form of affidavits or testimony, as the judge directs. If the judge finds that there is a reasonable probability that the informer can give the testimony, and the government elects not to disclose his identity, the judge on motion of the defendant in a criminal case shall dismiss the charges to which the testimony would relate, and the judge may do so on his own motion. In civil cases, he may make any order that justice requires. Evidence submitted to the judge 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 an order of court. All counsel shall be permitted to be present at any stage at which counsel for any party is permitted to be present.

(c) If information from an informer is relied upon to establish the legality of the means by which evidence was obtained and the judge is not satisfied that the information was received from an informer reasonably believed to be reliable or credible, he may require the identity of the informer to be disclosed. The judge shall, on request of the government, direct that the disclosure be made in camera. All counsel and parties concerned with the issue of legality shall be permitted to be present at every stage of proceedings under this subdivision except a disclosure in camera, at which no counsel or party shall be permitted to be present. If disclosure of the identity of the informer is made in camera, the record thereof 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 government.