The Supreme Court’s right to privacy is not written into the Constitution; the Court has built it, case by case, from several amendments working together. Beginning in 1965, the justices have recognized privacy interests in contraception, marriage, parenting, intimate conduct, and the data our phones generate about us. Some of those protections have grown. One of the biggest, the right to abortion, was taken back in 2022. Understanding where privacy law stands means tracing both halves of the doctrine: the personal-autonomy cases rooted in due process, and the surveillance cases rooted in the Fourth Amendment.
Where the Right to Privacy Came From
The foundational case is Griswold v. Connecticut (1965). A Connecticut law made it a crime to use contraceptives, even for married couples. The Court struck it down and announced the idea that would carry privacy law for decades: specific guarantees in the Bill of Rights have “penumbras,” shadows that create broader zones of privacy the government cannot enter.
Writing for the majority, Justice William O. Douglas drew those zones from several amendments at once. The First protects freedom of association. The Third bars quartering soldiers in private homes. The Fourth guards against unreasonable searches. The Fifth protects against forced self-incrimination. And the Ninth states that listing certain rights does not deny others “retained by the people.”1Justia U.S. Supreme Court Center. Griswold v. Connecticut, 381 U.S. 479 (1965)
Griswold’s principle has echoed through every privacy case since: the government cannot intrude into deeply personal decisions simply because the Constitution does not mention them by name.
Personal and Family Decisions
The Court quickly extended Griswold beyond married couples. In Eisenstadt v. Baird (1972), Massachusetts had banned distributing contraceptives to unmarried people while allowing married couples access. The Court struck down the law under the Equal Protection Clause, holding that the right to privacy belongs to individuals, not just to married couples.2Justia U.S. Supreme Court Center. Eisenstadt v. Baird, 405 U.S. 438 (1972)
Parental decisions sit in the same family of rights. The Court has treated the right of parents to direct the care, custody, and upbringing of their children as one of the oldest fundamental liberties it recognizes, as it put the point in Troxel v. Granville (2000).3Legal Information Institute. Troxel v. Granville
The autonomy strand reached marriage itself in Obergefell v. Hodges (2015). In a 5–4 ruling, the Court held that state bans on same-sex marriage violated both the Due Process Clause and the Equal Protection Clause of the Fourteenth Amendment. Justice Anthony Kennedy’s majority opinion described marriage as central to individual autonomy and held that same-sex couples are entitled to marry on the same terms as opposite-sex couples.4Legal Information Institute. Obergefell v. Hodges
Abortion: From Roe to Dobbs
No branch of privacy law has been more contested than abortion. In Roe v. Wade (1973), the Court held that the right to privacy was broad enough to cover a woman’s decision to end a pregnancy. The ruling imposed a trimester framework: in the first trimester the decision belonged to the woman and her doctor; in the second, the state could regulate to protect maternal health; after fetal viability it could restrict or ban abortion except where the mother’s life or health was at risk.5Justia U.S. Supreme Court Center. Roe v. Wade, 410 U.S. 113 (1973)
Planned Parenthood v. Casey (1992) kept what the Court called Roe’s “essential holding” but replaced the trimester framework. Under Casey, a pre-viability abortion regulation was unconstitutional only if it placed a “substantial obstacle” in the path of a woman seeking the procedure. States could otherwise pass laws designed to inform the woman’s choice or express a preference for childbirth, as long as those measures did not amount to an “undue burden.”6Justia U.S. Supreme Court Center. Planned Parenthood of Southeastern Pa. v. Casey, 505 U.S. 833 (1992)
Both precedents fell in Dobbs v. Jackson Women’s Health Organization (2022). The case involved Mississippi’s Gestational Age Act, which banned most abortions after 15 weeks. In a 6–3 decision the Court overturned Roe and Casey and held that the Constitution does not confer a right to abortion. The majority applied a test asking whether an unenumerated right is “deeply rooted in this Nation’s history and tradition.” It noted that when the Fourteenth Amendment was ratified in 1868, three-quarters of the states had made abortion a crime at any stage of pregnancy. Authority to regulate abortion returned to state legislatures.7Supreme Court of the United States. Dobbs v. Jackson Womens Health Organization
Intimate Conduct in the Home
The Court has recognized a privacy interest in private behavior inside the home, even when the conduct is controversial. In Stanley v. Georgia (1969), police executing a search warrant for evidence of illegal bookmaking found obscene films in the suspect’s home. The Court held that the First and Fourteenth Amendments prevent the government from making it a crime to privately possess such materials. Justice Thurgood Marshall wrote that the government has “no business telling a man, sitting alone in his own house, what books he may read or what films he may watch.” Private possession was protected; production and distribution were not.
A more sweeping ruling came in Lawrence v. Texas (2003). Texas had criminalized sexual intimacy between people of the same sex. The Court struck down the law 6–3, directly overruling its 1986 decision in Bowers v. Hardwick, which had upheld a similar Georgia statute. The Court held that the liberty protected by the Fourteenth Amendment’s Due Process Clause extends to private, consensual sexual conduct between adults, and that the government cannot “demean their existence or control their destiny” by criminalizing it.8Legal Information Institute. Lawrence v. Texas
Privacy Against Government Surveillance
The other half of privacy doctrine runs through the Fourth Amendment’s bar on “unreasonable searches and seizures.” For much of American history, whether something counted as a search turned on physical trespass. That changed in 1967.
Reasonable Expectation of Privacy
In Katz v. United States (1967), the FBI attached a listening device to the outside of a public phone booth to record a suspect’s calls. No one broke in or touched his belongings. The Court held the recording was still an unconstitutional search, declaring that the Fourth Amendment “protects people, not places.”9Constitution Annotated, Congress.gov. Amdt4.3.3 Katz and Reasonable Expectation of Privacy Test
Justice John Marshall Harlan’s concurrence set out a two-part test that still governs. First, the person must actually expect privacy in the thing or place being searched. Second, that expectation must be one society recognizes as reasonable. Someone in a phone booth qualifies; someone shouting on a street corner does not.
Technology and the Home
In Kyllo v. United States (2001), federal agents used a thermal imaging device from outside a home to detect heat patterns consistent with high-intensity grow lamps. The Court held that when the government uses a device not in general public use to learn details about the inside of a home that could not otherwise be known without physical entry, the surveillance is a search requiring a warrant. The majority rejected the argument that the scan only read heat on outer walls, warning that such reasoning would leave homeowners “at the mercy of advancing technology.”10Legal Information Institute. Kyllo v. United States
United States v. Jones (2012) addressed physical tracking. Police attached a GPS device to a suspect’s car and tracked his movements for 28 days. The Court held the monitoring was a search. The majority rested on the physical act of attaching the device to the suspect’s property; several concurring justices argued that the longer-term tracking itself violated reasonable privacy expectations, regardless of any trespass.11Justia U.S. Supreme Court Center. United States v. Jones, 565 U.S. 400 (2012)
Digital Data
The Court moved decisively on digital privacy in Riley v. California (2014). After arresting a suspect, police searched his smartphone without a warrant. The Court unanimously held that the search-incident-to-arrest exception does not reach cell phone data. Modern smartphones, the Court wrote, hold a “digital record of nearly every aspect” of a person’s life, and routine warrantless searches of that data would expose far more than any physical search of a pocket.12Justia U.S. Supreme Court Center. Riley v. California, 573 U.S. 373 (2014)
Carpenter v. United States (2018) tackled a harder question. The FBI had obtained 127 days of cell-site location records from a suspect’s wireless carrier without a warrant, averaging 101 data points per day. The Court held that accessing this kind of comprehensive location history is a Fourth Amendment search. The data, the majority said, offers “an intimate window into a person’s life,” revealing where someone lives, works, worships, and socializes.13Cornell Law School Legal Information Institute. Carpenter v. United States
The Third-Party Doctrine
Carpenter mattered partly because it limited a longstanding rule. Under Smith v. Maryland (1979), people have no reasonable expectation of privacy in information they voluntarily hand over to a third party. In Smith, the police used a device at the phone company to record the numbers a suspect dialed, and the Court found this was not a search because the caller had knowingly shared those numbers with the carrier in the ordinary course of business.14Justia U.S. Supreme Court Center. Smith v. Maryland, 442 U.S. 735 (1979)
For decades, that doctrine gave the government broad access to records held by banks, phone companies, and other businesses without a warrant. Carpenter did not overrule Smith, but the majority found cell-site location data different in kind. People do not meaningfully “volunteer” location data to a carrier; the phone generates it automatically as a condition of use. The ruling signals that the third-party doctrine has limits when applied to the vast digital records modern technology creates about everyone.13Cornell Law School Legal Information Institute. Carpenter v. United States
Where the Right to Privacy Stands Now
Dobbs is the most significant shift in privacy law in decades, and its long-term reach is still unclear. The majority opinion tried to limit it, writing that “nothing in this opinion should be understood to cast doubt on precedents that do not concern abortion.” The Court distinguished abortion as “inherently different” because it involves what earlier cases had called “potential life.”7Supreme Court of the United States. Dobbs v. Jackson Womens Health Organization
Not every justice stopped there. In a concurrence, Justice Clarence Thomas argued that the Court should reconsider all of its substantive due process precedents in future cases, naming three in particular: Griswold (contraception), Lawrence (intimate conduct), and Obergefell (marriage equality). Thomas’s view is that the Due Process Clause protects only procedural rights, not the substantive liberty interests those cases relied on. No other justice joined that portion of his opinion, but it has driven ongoing debate about how secure those rulings are under Dobbs’s emphasis on “deeply rooted” historical traditions.7Supreme Court of the United States. Dobbs v. Jackson Womens Health Organization
The surveillance side of privacy law has been moving the other way. Riley and Carpenter show a Court that takes digital privacy seriously and will update old doctrines when technology outruns them. The two trajectories pull in opposite directions: the Court is narrowing the substantive due process basis for personal-autonomy privacy while expanding Fourth Amendment protection for data.
Eleven state constitutions contain an explicit right to privacy, including those of Alaska, California, Florida, Hawaii, Illinois, and Montana. These provisions can offer broader protection than the federal Constitution, and they are not affected by shifts in how the Supreme Court reads federal rights. For people living in those states, state constitutional privacy guarantees may matter more than federal ones in the years ahead.