John Paul Stevens

“ Surely, there is a significant difference between the general and well-settled expectation that strangers will not have direct access to the contents of private communications, on the one hand, and the rather theoretical expectation that an occasional homeowner would even care if anybody noticed the relative amounts of heat emanating from the walls of his house, on the other. It is pure hyperbole for the Court to suggest that refusing to extend the holding of Katz to this case would leave the homeowner at the mercy of “technology that could discern all human activity in the home.” ”

“ If nothing more than that sort of information could be obtained by using the devices in a public place to monitor emissions from a house, then their use would be no more objectionable than the use of the thermal imager in this case.
The application of the Court’s new rule to “any information regarding the interior of the home,” ante, at 6, is also unnecessarily broad. If it takes sensitive equipment to detect an odor that identifies criminal conduct and nothing else, the fact that the odor emanates from the interior of a home should not provide it with constitutional protection. ”

“ Greenwood, 486 U.S., at 41, so too public officials should not have to avert their senses or their equipment from detecting emissions in the public domain such as excessive heat, traces of smoke, suspicious odors, odorless gases, airborne particulates, or radioactive emissions, any of which could identify hazards to the community. In my judgment, monitoring such emissions with “sense-enhancing technology,” ante, at 6, and drawing useful conclusions from such monitoring, is an entirely reasonable public service.
On the other hand, the countervailing privacy interest is at best trivial. ”