Cite as: 533 U. S. 27 (2001)
Opinion of the Court
Fourth Amendment nonetheless protected Katz from the warrantless eavesdropping because he "justifiably relied" upon the privacy of the telephone booth. Id., at 353. As Justice Harlan's oft-quoted concurrence described it, a Fourth Amendment search occurs when the government violates a subjective expectation of privacy that society recognizes as reasonable. See id., at 361. We have subsequently applied this principle to hold that a Fourth Amendment search does not occur—even when the explicitly protected location of a house is concerned—unless "the individual manifested a subjective expectation of privacy in the object of the challenged search," and "society [is] willing to recognize that expectation as reasonable." Ciraolo, supra, at 211. We have applied this test in holding that it is not a search for the police to use a pen register at the phone company to determine what numbers were dialed in a private home, Smith v. Maryland, 442 U. S. 735, 743- 744 (1979), and we have applied the test on two different occasions in holding that aerial surveillance of private homes and surrounding areas does not constitute a search, Ciraolo, supra; Florida v. Riley, 488 U. S. 445 (1989).
The present case involves officers on a public street engaged in more than naked-eye surveillance of a home. We have previously reserved judgment as to how much technological enhancement of ordinary perception from such a vantage point, if any, is too much. While we upheld enhanced aerial photography of an industrial complex in Dow Chemical, we noted that we found "it important that this is not an area immediately adjacent to a private home, where privacy expectations are most heightened," 476 U. S., at 237, n. 4 (emphasis in original).
III
It would be foolish to contend that the degree of privacy secured to citizens by the Fourth Amendment has been
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