[6][2] Other examples include: pen registers that record the numbers dialed from particular telephones;[7] conversations with others, though there could be a Sixth Amendment violation if the police send an individual to question a defendant who has already been formally charged;[8] a person's physical characteristics, such as voice or handwriting;[9] 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;[10] anything in open fields (e.g., a barn);[11] 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;[12] and paint scrapings on the outside of a vehicle.
If a person did not undertake reasonable efforts to conceal something from a casual observer (as opposed to a snoop), then no subjective expectation of privacy is assumed.
The Supreme Court has also ruled that there is no objectively reasonable expectation of privacy (and thus no search) when officers hovering in a helicopter 400 feet above a suspect's house conduct surveillance.
However, scholars argue that lack of understanding of the Internet as either a public or private space leads to issues in defining expectations of the law.
[23] Cellphones receive Fourth Amendment protection because they no longer contain just phone logs and address books; they contain a person's most sensitive information that they believe will be kept private.
[24] In Florida v. Jardines on March 26, 2013, the U.S. Supreme Court ruled that police violated the Fourth Amendment rights of a homeowner when they led a drug-sniffing dog to the front door of a house suspected of being used to grow marijuana.
The court said the police officers violated a basic rule of the Fourth Amendment by physically intruding into the area surrounding a private home for investigative purposes without securing a warrant.
Scalia added: "This right would be of little practical value if the state's agents could stand in a home's porch or side garden and trawl for evidence with impunity."
In Missouri v. McNeely on April 17, 2013, the U.S. Supreme Court ruled that police must generally obtain a warrant before subjecting a drunken-driving suspect to a blood test.
In Katz v. United States on October 17, 1967, Justice Harlan created the Reasonable Expectation of Privacy Test in his concurring opinion.
[28] They asked these groups questions around the limits of using information technology such as the use of cookies, biometrics, loyalty cards, radio frequency identification, text messaging, pop-up advertisements, telemarketing, and spam.