Cite as: 533 U. S. 27 (2001)
Stevens, J., dissenting
did provide its user with the functional equivalent of access to a private place—such as, for example, the telephone booth involved in Katz, or an office building—then the rule should apply to such an area as well as to a home. See Katz, 389 U. S., at 351 ("[T]he Fourth Amendment protects people, not places").
The final requirement of the Court's new rule, that the information "could not otherwise have been obtained without physical intrusion into a constitutionally protected area," ante, at 34 (internal quotation marks omitted), also extends too far as the Court applies it. As noted, the Court effectively treats the mental process of analyzing data obtained from external sources as the equivalent of a physical intrusion into the home. See supra, at 44. As I have explained, however, the process of drawing inferences from data in the public domain should not be characterized as a search.
The two reasons advanced by the Court as justifications for the adoption of its new rule are both unpersuasive. First, the Court suggests that its rule is compelled by our holding in Katz, because in that case, as in this, the surveillance consisted of nothing more than the monitoring of waves emanating from a private area into the public domain. See ante, at 35. Yet there are critical differences between the cases. In Katz, the electronic listening device attached to the outside of the phone booth allowed the officers to pick up the content of the conversation inside the booth, making them the functional equivalent of intruders because they gathered information that was otherwise available only to someone inside the private area; it would be as if, in this case, the thermal imager presented a view of the heat-generating activity inside petitioner's home. By contrast, the thermal imager here disclosed only the relative amounts of heat radiating from the house; it would be as if, in Katz, the listening device disclosed only the rela-
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