Constitution Check: Does the Fourth Amendment protect the privacy of telephone conversations?

Lyle Denniston looks at recent remarks by Justice Antonin Scalia that the Fourth Amendment might not prevent the government from listening to your phone calls.


“Supreme Court Justice Antonin Scalia made it clear the issue [of National Security Agency surveillance of Americans] would likely come before the high court, and he hinted he would rule that ‘conversations’ (i.e., the conversations that the government might listen to) aren’t protected by the Fourth Amendment.  The Fourth Amendment, Scalia pointed out, prohibits the government from searching our “persons, houses, papers, and effects” without a warrant – not ‘conversations.’ ”

 – Excerpt from a story by Erin Fuchs on the Business Insider website on March 22, about an appearance by Justice Scalia before students of the Brooklyn Law School in New York City.


When a Justice of the Supreme Court, speaking outside the court, makes a comment on the meaning of the Constitution, one can never say for sure that such a remark is wrong: the Justice can always try to persuade other members of the court to rule that way, sooner or later.

But in order for telephone conversations to be placed outside the privacy protections of the Fourth Amendment, a majority of the court would have to be persuaded to overrule several of its most important decisions limiting the government’s power to eavesdrop on private conversations without a search warrant.

Justice Scalia’s comment (if accurately recounted), that the Fourth Amendment does not protect telephone conversations, at one time was, in fact, the court’s view.   In the Prohibition era case of Olmstead v. U.S., in 1928, the Supreme Court decided a case involving a crude form of physical wiretapping to listen to the conversations of liquor dealers.  The court said explicitly: “One who installs in his house a telephone instrument with connecting wires intends to project his voice to those quite outside, and…the wires beyond his house and messages while passing over them are not within the protection of the Fourth Amendment.”

That decision established the privacy principle that, unless government agents intruded physically into a constitutionally protected area, such as carrying out a “trespass” inside the home, there was no violation of the Fourth Amendment.

In 1961, the Supreme Court was asked to overrule the Olmstead decision, in a case involving the use of a microphone on the end of a long pole that was poked through a wall to enable federal agents to listen in on gamblers’ conversations.  The court had been told that advancing technology made it easier for government to intrude into private spaces, so the Fourth Amendment should take account of that.

In that case, Silverman v. U.S., the court said it need not delve into “the large questions which have been argued,” based on “the vaunted marvels of the electronic age,” because this case involved a physical invasion into or encroachment on a private space.  It thus ruled that the use by the agents of a “spike mike” did violate the Fourth Amendment.

What is at least implicit in the court’s perspective, at least by the time of the Silverman decision, was that there could be factual scenarios in which government eavesdropping on private conversations was an unconstitutional invasion of privacy.

The Supreme Court went further, in the 1967 decision in Katz v. U.S.   That case, involving an illegal gambling prosecution, challenged federal agents’ use of a device from outside of a telephone booth that had been used by a suspect to make bets.  The court did what it had refused to do in the Silverman case: it cast aside the Olmstead view that there could be no Fourth Amendment violation unless eavesdropping was done by a physical intrusion into a private space.

The Fourth Amendment, the court said, “protects people, not places.” So it abandoned the notion that the Fourth Amendment applied only to private physical space or areas.  Instead, the court adopted the concept that what an individual “seeks to preserve as private, even in an area accessible to the public, may be constitutionally protected.”

When an individual steps into a telephone booth, closes the door and puts a coin in the slot, that individual, the court said, “is surely entitled to assume that the words he utters into the mouthpiece will not be broadcast to the world.  To read the Constitution more narrowly is to ignore the vital role that the public telephone has come to play in private communication.”

The court stressed in that case, however, that it was not ruling on a scenario in which government agents had eavesdropped, without a warrant, on a suspect in a case involving “national security.”

Five years later, the Supreme Court took up that open question, in the case of U.S. v. U.S. District Court, involving government eavesdropping on the conversations of suspects in the dynamite bombing of a Central Intelligence Agency office in Ann Arbor, Mich.   Relying on what it had said in the Katz and Silverman cases about eavesdropping in ordinary criminal cases, the court ruled that there is no national security exemption to the Fourth Amendment requirement that the government obtain a warrant before conducting surveillance of telephone conversations.

“Those charged with investigative and prosecutorial duty,” the court said, “should not be the sole judges of when to utilize constitutionally sensitive means in pursuing their tasks.”

The National Security Agency’s global program of monitoring telephone calls, as well as Internet and cable communications, one day – perhaps soon – will be tested in the Supreme Court, under the Fourth Amendment.  There will be a lengthy history of constitutional protection for the privacy of conversations that will be at stake, and Justice Scalia probably will be on the court then to say – in his formal role as a judge – whether that history was all a mistake.

Lyle Denniston is the National Constitution Center’s adviser on constitutional literacy. He has reported on the Supreme Court for 55 years, currently covering it for SCOTUSblog, an online clearinghouse of information about the Supreme Court’s work.

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