Also known as: protect people not places · Fourth Amendment protects people not places · Katz principle · reasonable expectation of privacy
Written by attorneys · grounded in primary & secondary sources — see below
A foundational principle of Fourth Amendment jurisprudence holding that constitutional protection extends to individuals' reasonable expectations of privacy rather than to particular physical locations. A search occurs when government conduct violates a person's subjective expectation of privacy that society recognizes as reasonable. What a person knowingly exposes to the public lacks protection even if the exposure occurs inside a home or office.
Select any source to read its text and confirm it supports the definition.
Patrick Phan places several opaque bags of household refuse at the edge of his driveway for scheduled pickup. Officers collect the bags without a warrant and discover evidence of illegal activity inside. Because Phan left the bags in an area accessible to the public, he held no reasonable expectation of privacy in their contents under the principle.
Pierre Poulin's wireless carrier releases four months of his historical cell-site location information to investigators pursuant to a court order lacking probable cause. The records reveal repeated visits to a private location. Under the principle, Poulin retains a reasonable expectation of privacy in the pervasive, long-term location data even though the carrier holds the records.
Pedro Pacheco stays overnight as a guest in Paula Pierce's home. Officers enter the residence without a warrant and seize items belonging to Pacheco. Because Pacheco exhibited a subjective expectation of privacy in the home that society recognizes as reasonable, the principle affords him standing to challenge the search.
Portia Price enters a public telephone booth, closes the door, and speaks in a low voice during a call. Officers attach a listening device to the outside of the booth without a warrant. The principle establishes that Price's reasonable expectation of privacy in the conversation triggers Fourth Amendment protection even though the booth is located in a public area.
Perry Pratt, a public hospital patient, provides a urine sample under a policy requiring testing of all pregnant patients for cocaine. Hospital staff turn positive results over to law enforcement without warrants. The principle requires the court to examine whether Pratt held a reasonable expectation of privacy in the medical information rather than focusing solely on the hospital setting.
Pioneer Energy drivers are stopped at a city-operated checkpoint where officers use drug-sniffing dogs on every vehicle without individualized suspicion. The company challenges the program as an unreasonable seizure. The principle directs analysis to whether the drivers maintained a reasonable expectation of privacy in their vehicles' contents during the brief, suspicionless encounter rather than treating the highway as an unprotected place.
No. The principle recognizes that a person may retain a reasonable expectation of privacy in information or items even when physically present in an area accessible to others, provided the person seeks to preserve that information as private.
Supporting sources
A defendant must demonstrate a personal reasonable expectation of privacy in the place searched. An overnight guest typically satisfies this test, while a short-term visitor present only for a commercial transaction generally does not.
…(a) that an enclosed telephone booth is an area where, like a home and unlike a field, a person has a constitutionally protected reasonable expectation of privacy; (b) that electronic as well as physical intrusion into a place that is in this sense private may constitute a violation of the Fourth Amendment; and (c) that the invasion of a…
…this Term, for example, we held that while an aerial observation from a helicopter hovering at 400 feet does not violate any reasonable expectation of privacy
…meaningfully interferes with freedom of movement, and obtaining and examining evidence may be a search when it infringes a
…proceedings, but on limited grounds and as to some causes of action only. First, the Court of Appeal held plaintiffs had no reasonable expectation of privacy
…of having strangers take it,” United States v. Reicherter , 647 F. 2d 397, 399 (CA3 1981), respondents could have had no reasonable expectation of privacy
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No. Individuals retain a reasonable expectation of privacy in historical cell-site location records that reveal pervasive, long-term movements even though the records are stored by a service provider.
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Justice Harlan's two-part inquiry asks first whether the person exhibited an actual subjective expectation of privacy and second whether that expectation is one society is prepared to recognize as reasonable.
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No. A person who leaves opaque trash bags on a public street for pickup has no reasonable expectation of privacy in the contents because the bags are readily accessible to members of the public.
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