In United States v. Green, 216 U.S. App. D.C. 329, 670 F.2d 1148, 1156 (D.C. Cir. 1981), a D.C. police officer was stationed at an undisclosed location in a known drug trafficking area. Green, 670 F.2d at 1150.
The officer saw what he believed to be a "two-party drug transaction" where one "receives the money from a customer, carries it to the individual holding the drugs, and returns the purchased drugs to the customer." Id. 670 F.2d at 1151, n.1.
Based on what he saw from his hidden surveillance, the officer radioed a description of the people involved to other officers who made the arrest. Id. 670 F.2d at 1151.
The Court in Green analogized the disclosure of a covert surveillance location to issues involving the anonymity of government informants, concluding that the policy considerations protecting informants exist in undisclosed location cases. Id. 670 F.2d at 1154-55.
The Green court concluded that both secret informants and secret locations are helpful only if they remain undisclosed. Id. 670 F.2d at 1155. Revealing the hidden location (or unnamed informer) may jeopardize the safety of officers or citizens and discourage further public cooperation with the police. Id. 670 F.2d at 1155. These similarities persuaded the Green court to recognize a qualified "surveillance location privilege." Id.
After recognizing the existence of the privilege, the Green court balanced the state's privilege not to disclose against the accused's general right to cross-examination. Id. 670 F.2d at 1154.