The Text
The Fourth Amendment — What It Actually Says
“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.”
— Fourth Amendment, United States Constitution, 1791
Notice what it doesn’t say. It doesn’t say “privacy.” It says secure. It says your persons, houses, papers, and effects. It was written by people who had experienced British soldiers with general warrants — open-ended documents that let them search anything, anywhere, anytime, for any reason. The Fourth Amendment was a direct reaction to that. Its entire purpose was to force the government to have a specific reason, targeting a specific person, in a specific place, before it could look through your things. That purpose is now almost entirely defeated — but not by the government changing the law. By the law failing to keep up with technology.
Where the Right to Privacy Actually Comes From
The Constitution doesn’t say the word “privacy” once. Courts had to find it — and the way they found it shapes everything that follows.
The story starts in 1890, when future Supreme Court Justice Louis Brandeis co-wrote a Harvard Law Review article arguing that the law should recognize “the right to be let alone” — the most comprehensive of rights and the right most valued by civilized men. It was a response to newspapers printing gossip. It was visionary. It was also not law.
Privacy as a constitutional right was constructed slowly, case by case. It wasn’t explicitly in the Bill of Rights. Courts found it in the “penumbras” — the shadows — of other amendments. The First Amendment protects your right to hold beliefs privately. The Third Amendment prohibits soldiers being quartered in your home. The Fourth protects your papers. The Fifth protects you from self-incrimination. Together, courts said, these create a zone of privacy.
FoundationalBrandeis and Warren — "The Right to Be Let Alone"
Samuel Warren and Louis Brandeis publish the most influential law review article in American history, arguing that privacy is a fundamental right that the law should protect. Not yet law — but it plants the seed for everything that follows.
Landmark WinGriswold v. Connecticut — Privacy Becomes Constitutional
The Supreme Court strikes down a law banning contraception, finding a constitutional right to privacy in the “penumbras” of the Bill of Rights. Justice Douglas: the state cannot search “the sacred precincts of marital bedrooms.” This is the first time the Supreme Court explicitly holds that the Constitution protects privacy.
Landmark WinKatz v. United States — Privacy Follows the Person, Not Just the Place
FBI wiretaps a phone booth without physically entering it. Supreme Court rules this is still a search. Justice Harlan establishes the “reasonable expectation of privacy” test. But Katz also plants a fatal seed: “what a person knowingly exposes to the public... is not a subject of Fourth Amendment protection.” That sentence will be used to gut privacy for the next six decades.
Erosion BeginsUnited States v. Miller — Bank Records Are Not Yours
Government subpoenas your bank records. No warrant. Supreme Court says no violation: you shared that information with the bank, so you have no expectation of privacy in it. You “assumed the risk” that the bank would share it with the government. This is the birth of the third-party doctrine — the rule that will eventually swallow privacy whole.
Doctrine ExpandsSmith v. Maryland — Phone Numbers You Dial Are Not Private
Police install a pen register on a robbery suspect’s phone, recording every number he dials. No warrant. Supreme Court rules: phone numbers you dial are shared with the phone company, so you have no Fourth Amendment protection in them. The third-party doctrine now covers not just what you say, but who you call, and the pattern of your communications.
Partial RecoveryCarpenter v. United States — Location History Needs a Warrant
Government gets 127 days of cell phone location data without a warrant. Supreme Court rules this violates the Fourth Amendment. Chief Justice Roberts: this data provides “an intimate window into a person’s life.” First time in decades the Court restricts the third-party doctrine — but the ruling is deliberately narrow, leaving most digital data unprotected.
ActiveChatrie v. United States — Geofence Warrants Before the Supreme Court
Supreme Court granted certiorari in January 2026 to decide whether geofence warrants — which ask Google for data on every device in an area during a time window — violate the Fourth Amendment. Could be the most significant privacy ruling since Carpenter.