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, known as the Katz test, was formulated in a concurring opinion by Justice John Marshall Harlan II. The Katz test has since been used in numerous cases, particularly because of technological advances that create new questions about privacy norms and government surveillance of personal data. Background Charles Katz was a sports bettor who by the mid-1960s had become "probably the preeminent college basketball handicapper in America." In 1965, Katz regularly used a public telephone booth near his apartment on Sunset Boulevard in Los Angeles to communicate his gambling handicaps to bookmakers in Boston and Miami. Unbeknownst to Katz, the FBI had begun investigating his gambling activities and was recording his conversations via a covert listening device attached to the outside of the phone booth. After recording many of his phone calls, FBI agents arrested Katz and charged him with eight counts of knowingly transmitting wagering information by telephone between U.S. states, which is a federal crime under Section 18 of the United States Code, particularly a law on the transmission of wagering information. Katz was tried in the U.S. District Court for the Southern District of California. Katz made a motion to suppress the FBI's recordings, arguing that because the agents did not have a search warrant allowing them to place their listening device, the recordings had been made in violation of the Fourth Amendment and should be inadmissible in court per the exclusionary rule. The judge denied Katz's motion and ruled that the recordings were admissible as evidence, and Katz was convicted based on them. Katz appealed his conviction to the U.S. Court of Appeals for the Ninth Circuit. In 1966, the Ninth Circuit affirmed Katz's conviction, ruling that because the FBI's eavesdropping device did not physically penetrate the telephone booth's wall, no Fourth Amendment search occurred, and so the FBI did not need a warrant to place the device. Katz then appealed to the Supreme Court, which