Before 1967 the Court focused on the concept of “constitutionally protected areas” to define the privacy protected by the Fourth Amendment; for example, a person’s dwelling was recognized as such an area, as was the “curtilage” property immediately surrounding the dwelling, but not the “open fields” property surrounding the curtilage. After the decision in Katz v. United States, the Court shifted its focus to protect a defendant’s “privacy interest” when a person manifests a subjective expectation of privacy, and the expectation is “reasonable” in light of societal understandings.
Simple technology that enhances the five senses, such as a flashlight, does not violate a person’s expectation of privacy. The constitutionality of the warrantless use of more complex technology requires case-by-case analysis.
The Court has examined and rejected privacy claims on a case-by-case basis with regard to these interests: 1) a conversation recorded by an informant who is a trusted confederate; 2) the visual inspection of open fields by trespassing police; 3) the examination of garbage left on the curb for collection; 4) a dog sniff of luggage or of the exterior of a car by a trained narcotics-detection dog; 5) the use of a radio transmitter “beeper” to track an object to a location that is not in a dwelling and could have been obtained by visual surveillance; 6) a helicopter flyover of the curtilage of a dwelling in lawful airspace for the flying public; and 7) the use of an aerial mapping camera to take photographs during a flyover of business property.
The Court has examined and recognized privacy claims on a case-by-case basis with regard to these interests: 1) a conversation in a public phone booth recorded by the police; 2) the visual inspection of curtilage area surrounding a dwelling by trespassing police; 3) manual inspection of luggage by squeezing it; 4) the use of a radio transmitter “beeper” to track an object to a location that is inside a dwelling; 5) the use of an infrared thermal imagining device aimed at a dwelling to detect the emanation of heat.