The Fourth Amendment to the United States Constitution is part of the Bill of Rights. It prohibits unreasonable searches and seizures and sets requirements for issuing warrants: warrants must be issued by a judge or magistrate, justified by probable cause, supported by oath or affirmation, and must particularly describe the place to be searched and the persons or things to be seized.
Katz v. United States, 389 U.S. 347 (1967), was a landmark decision of the U.S. Supreme Court in which the Court redefined what constitutes a "search" or "seizure" with regard to the protections of the Fourth Amendment to the U.S. Constitution. The ruling expanded the Fourth Amendment's protections from an individual's "persons, houses, papers, and effects", as specified in the Constitution's text, to include any areas where a person has a "reasonable expectation of privacy". The reasonable expectation of privacy standard, now known as the Katz test, was formulated in a concurring opinion by Justice John Marshall Harlan II.
California v. Greenwood, 486 U.S. 35 (1988), was a case in which the Supreme Court of the United States held that the Fourth Amendment does not prohibit the warrantless search and seizure of garbage left for collection outside the curtilage of a home.
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. Overall, expectations of privacy can be subjective or objective.
California v. Ciraolo, 476 U.S. 207 (1986), was a decision by the Supreme Court of the United States in which the Court held that aerial observation of a person's backyard by police, even if done without a search warrant, does not violate the Fourth Amendment to the U.S. Constitution.
In United States criminal law, the border search exception is a doctrine that allows searches and seizures at international borders and their functional equivalent without a warrant or probable cause. Generally speaking, searches within 100 miles of the border are more permissible without a warrant than those conducted elsewhere in the U.S. The doctrine also allows federal agents to search people at border crossings without a warrant or probable cause. The government is allowed to use scanning devices and to search personal electronics. Invasive bodily searches, however, require reasonable suspicion.
California v. Carney, 471 U.S. 386 (1985), was a United States Supreme Court case which held that a motor home was subject to the automobile exception to the search warrant requirement of the Fourth Amendment to the United States Constitution because the motor home was readily movable.
United States v. White, 401 U.S. 745 (1971), was a United States Supreme Court decision which held that recording conversations using concealed radio transmitters worn by informants does not violate the Fourth Amendment protection against unreasonable searches and seizures, and thus does not require a warrant.
Horton v. California, 496 U.S. 128 (1990), was a United States Supreme Court case in which the Court held that the Fourth Amendment does not prohibit the warrantless seizure of evidence which is in plain view. The discovery of the evidence does not have to be inadvertent, although that is a characteristic of most legitimate plain-view seizures. The opinion clarified the plain view doctrine of the Court's Fourth Amendment analysis.
Ontario v. Quon, 560 U.S. 746 (2010), is a United States Supreme Court case concerning the extent to which the right to privacy applies to electronic communications in a government workplace. It was an appeal by the city of Ontario, California, from a Ninth Circuit decision holding that it had violated the Fourth Amendment rights of two of its police officers when it disciplined them following an audit of pager text messages that discovered many of those messages were personal in nature, some sexually explicit. The Court unanimously held that the audit was work-related and thus did not violate the Fourth Amendment's protections against unreasonable search and seizure.
United States v. Warshak, 631 F.3d 266 is a criminal case decided by the United States Court of Appeals for the Sixth Circuit holding that government agents violated the defendant's Fourth Amendment rights by compelling his Internet service provider (ISP) to turn over his emails without first obtaining a search warrant based on probable cause. However, constitutional violation notwithstanding, the evidence obtained with these emails was admissible at trial because the government agents relied in good faith on the Stored Communications Act (SCA). The court further declared that the SCA is unconstitutional to the extent that it allows the government to obtain emails without a warrant.
Mancusi v. DeForte, 392 U.S. 364 (1968), is a decision of the United States Supreme Court on privacy and the Fourth Amendment. It originated in the lower courts as United States ex rel. Frank DeForte, appellant v. Vincent R. Mancusi, Warden of Attica Prison, Attica, New York, appellee, a petition for a writ of habeas corpus by a prisoner who had exhausted all his state appeals. By a 6–3 margin the Court affirmed the United States Court of Appeals for the Second Circuit's reversal of a district court denial of the petition.
United States v. Graham, 846 F. Supp. 2d 384, was a Maryland District Court case in which the Court held that historical cell site location data is not protected by the Fourth Amendment. Reacting to the precedent established by the recent Supreme Court case United States v. Jones in conjunction with the application of the third party doctrine, Judge Richard D. Bennett found that "information voluntarily disclosed to a third party ceases to enjoy Fourth Amendment protection" because that information no longer belongs to the consumer, but rather to the telecommunications company that handles the transmissions records. The historical cell site location data is then not subject to the privacy protections afforded by the Fourth Amendment standard of probable cause, but rather to the Stored Communications Act, which governs the voluntary or compelled disclosure of stored electronic communications records.
The third-party doctrine is a United States legal doctrine that holds that people who voluntarily give information to third parties—such as banks, phone companies, internet service providers (ISPs), and e-mail servers—have "no reasonable expectation of privacy" in that information. A lack of privacy protection allows the United States government to obtain information from third parties without a legal warrant and without otherwise complying with the Fourth Amendment prohibition against search and seizure without probable cause and a judicial search warrant.
United States v. Quartavious Davis is a United States federal legal case that challenged the use in a criminal trial of location data obtained without a search warrant from MetroPCS, a cell phone service provider. Mobile phone tracking data had helped place the defendant in this case at the scene of several crimes, for which he was convicted. The defendant appealed to the Eleventh Circuit Court of Appeals, which found the warrantless data collection had violated his constitutional rights under the Fourth Amendment to the United States Constitution, but declined to order a new trial because the evidence was collected in good faith. The Eleventh Circuit has since vacated this decision pending a rehearing by the Eleventh Circuit en banc. United States v. Davis, 573 Fed. Appx. 925. On 5 May 2015, the en banc order upheld the use of the information. On 9th Nov 2015, the Supreme Court of the United States declined to hear this case on appeal.
Los Angeles v. Patel, 576 U.S. 409 (2015), was a United States Supreme Court case in which the Court held that a Los Angeles law, Municipal Code § 41.49, requiring hotel operators to retain records about guests for a ninety-day period is facially unconstitutional under the Fourth Amendment to the United States Constitution because it does not allow for pre-compliance review.
Dow Chemical Co. v. United States, 476 U.S. 227 (1986), was a United States Supreme Court case decided in 1986 dealing with the right to privacy and advanced technology of aerial surveillance.
Carpenter v. United States, 585 U.S. 296, 138 S.Ct. 2206 (2018), is a landmark United States Supreme Court case concerning the privacy of historical cell site location information (CSLI). The Court held that the government violates the Fourth Amendment to the United States Constitution when it accesses historical CSLI records containing the physical locations of cellphones without a search warrant.
California Bankers Assn. v. Shultz, 416 U.S. 21 (1974), was a US Supreme Court case in which the Court held that the Bank Secrecy Act, passed by Congress in 1970 requiring banks to record all transactions and report certain domestic and foreign transactions of high dollar amounts to the United States Treasury, did not violate the First, Fourth, and Fifth Amendments of the US Constitution.
United States v. Gratkowski, 964 F.3d 307, was a case in the United States Court of Appeals for the Fifth Circuit involving the Fourth Amendment implications of Bitcoin transactions.
