In 1967, the Supreme Court ruled that a telephone caller has a right to expect privacy
The Fourth Amendment of the Constitution provides that “the right of the people to be secure in their persons, houses, papers and effects, against unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.”
That provision was adapted from English common law practice. But it leaves unanswered some important questions. What exactly is a “search and seizure”? And can evidence produced in an illegal search and seizure be used by the government to secure a criminal conviction?
The Supreme Court answered the second question in the 1914 case of Weeks v. United States. The defendant was accused of using the mails to transport lottery tickets, in violation of federal law. At trial, the government used evidence produced in a search of his house for which a warrant was not obtained. The Court ruled that the evidence could not be used and that the conviction must be overturned.
Weeks involved what was clearly a search, as understood at the time of the passage of the Fourth Amendment. But was evidence obtained through wiretapping by federal law enforcement the result of a search? The nation’s highest Court faced that issue in the 1928 case of Olmstead v. United States, which involved enforcement of federal Prohibition laws.
The judges split 5-4. The majority opinion by Chief Justice Howard Taft ruled that wiretapping did not constitute a search. Unlike cases where law enforcement officers opened a suspect’s mail, in violation of federal law, wiretapping did not amount to a physical invasion of the defendant’s space, he argued. In a dissent, Justice Louis D. Brandeis argued that a wiretap did amount to a violation of “the right of the people to be secure in their persons.” Technological developments unanticipated by the Framers of the Fourth Amendment allowed the government to invade that space just like opening a letter.
Brandeis’s opinion proved persuasive to many legal commentators. In the 1967 case of Katz v. United States, involving a wiretap of a phone call transmitting illegal bets — by a 7-1 majority, the Court overruled Olmstead on the grounds that a telephone caller has an expectation of enjoying a right of privacy.