Warrantless searches are, “subject only to a few specifically established and well-delineated exceptions,” per se unreasonable and are therefore prohibited by the Fourth Amendment. Katz v. United States, supra, 389 U.S. at 357, 88 S.Ct. at 514; Schneckloth v. Bustamonte, 412 U.S. 218, 219, 93 S.Ct. 2041, 2043, 36 L.Ed.2d 854 (1973); Coolidge v. New Hampshire, 403 U.S. 443, 454-55, 91 S.Ct. 2022, 2031-32, 29 L.Ed.2d 564 (1971). The threshold question in the present case is whether observation by means of a high-powered telescope constitutes the type of intrusion against which the Fourth Amendment protects. The answer depends on whether such surveillance violated reasonable expectations of privacy.
The only Supreme Court discussions of the constitutional implications of surveillance with optical devices are dicta in two elderly cases, in which, as the government puts it, the Court accepted it “as a given” that use of such devices did not constitute an unreasonable search and seizure. See On Lee v. United States, 343 U.S. 747, 72 S.Ct. 967, 96 L.Ed. 1270 (1952); United States v. Lee, 274 U.S. 559, 47 S.Ct. 746, 71 L.Ed. 1202 (1927). In Lee, the Court considered the use of a search light by Coast Guard officers to observe the deck of a vessel at sea. The use of the light was upheld with the observation that “(s)uch use of a search light is comparable to the use of a marine glass or a field glass. It is not prohibited by the Constitution.” 274 U.S. at 563, 47 S.Ct. at 748. In On Lee, the Court dealt with the use of a radio transmitter to overhear a conversation between the defendant and an undercover agent. The Court observed that the defendant was talking “indiscreetly” with someone he trusted, who was lawfully on his premises; and the fact that he was overheard by means of the transmitter and a receiver rather than by an agent simply standing outside an open window was held immaterial to Fourth Amendment analysis. Again the Court analogized to visual aids:
The use of bifocals, field glasses or the telescope to magnify the object of a witness’ vision is not a forbidden search or seizure, even if they focus without his knowledge or consent upon what one supposes to be private indiscretions.
343 U.S. at 754, 72 S.Ct. at 972.
While these statements were dicta, they were entirely consistent with Fourth Amendment analysis then prevailing, which depended heavily on common law concepts of trespass. Under those precepts, emphasis was laid on such questions as whether or not the agents had physically penetrated the subject’s property, see, e. g., Silverman v. United States, 365 U.S. 505, 512, 81 S.Ct. 679, 683, 5 L.Ed.2d 734 (1961); Goldman v. United States, 316 U.S. 129, 62 S.Ct. 993, 86 L.Ed. 1322 (1942), or were otherwise within the curtilage, see Hester v. United States, 265 U.S. 57, 44 S.Ct. 445, 68 L.Ed. 898 (1924). See generally 1 La Fave, Search and Seizure: A Treatise on the Fourth Amendment 257 (1978); Amsterdam, Perspectives on the Fourth Amendment, 58 Minn.L.Rev. 349, 357 (1974).
In 1967, however, with the decision in Katz v. United States, supra, Fourth Amendment analysis entered a new era as the Court held that trespass concepts were no longer controlling. Katz ruled that the government’s listening to one side of a telephone conversation by means of electronic equipment placed on the outside of a telephone booth located in a public place was a search in violation of the Fourth Amendment. Justice Stewart, writing for the Court, stated that notions of protected areas were no longer necessarily useful, observing that
(w)hat a person knowingly exposes to the public, even in his own home or office, is not a subject of Fourth Amendment protection… But what he seeks to preserve as private, even in an area accessible to the public, may be constitutionally protected.
389 U.S. at 351-52, 88 S.Ct. at 511-12. The Court held that the evidence gleaned from the agents’ electronic eavesdropping at the booth could not be used against Katz at his trial because the use of the device “violated the privacy upon which he justifiably relied while using the telephone booth and thus constituted a ‘search and seizure’ within the meaning of the Fourth Amendment.” Id. at 353, 88 S.Ct. at 512. Justice Harlan, concurring, distilled from Katz and its antecedents “a twofold requirement, first that a person have exhibited an actual (subjective) expectation of privacy and, second, that the expectation be one that society is prepared to recognize as ‘reasonable.’ ” Id. at 361, 88 S.Ct. at 516.
