Expectation of privacy (United States)

In United States constitutional law, expectation of privacy is a legal test which is crucial in defining the scope of the applicability of the privacy protections of the Fourth Amendment to the U.S. Constitution. It is related to, but is not the same as, a right to privacy, a much broader concept which is found in many legal systems (see privacy law). Overall, expectations of privacy can be subjective or objective. There are two types of expectations of privacy: Subjective expectation of privacy: a certain individual's opinion that a certain location or situation is private which varies greatly from person to person Objective, legitimate, reasonable expectation of privacy: an expectation of privacy generally recognized by society and perhaps protected by law. Places where individuals expect privacy include residences, hotel rooms, or public places that have been provided by businesses or the public sector to ensure privacy, including public restrooms, private portions of jailhouses, or phone booths. This expectation extends against both physical and digital intrusions, and even cell tower geolocation data is protected. In general, one cannot have a reasonable expectation of privacy for things put into a public space. There are no privacy rights in garbage left for collection in a public place. Other examples include: pen registers that record the numbers dialed from particular telephones; conversations with others, though there could be a Sixth Amendment violation if the police sends an individual to question a defendant who has already been formally charged; a person's physical characteristics, such as voice and handwriting; what is observed pursuant to aerial surveillance that is conducted in public navigable airspace not using equipment that unreasonably enhances the surveying government official's vision; anything in open fields (e.g., a barn); smells that can be detected by the use of a drug-sniffing dog during a routine traffic stop, even if the government official did not have probable cause or reasonable suspicion to suspect that drugs were present in the defendant's vehicle; and paint scrapings on the outside of a vehicle.