The case in one breath To tie Timothy Carpenter to a string of robberies, the FBI didn’t follow him — it asked his phone companies where he’d been. They handed over 127 days of location records: nearly 13,000 points mapping his movements, no warrantWarrant: a judge’s permission for a search, issued only on probable cause. The government had used a lower-standard court order instead — the exact shortcut this case closed. required, because the records “belonged” to the carriers. In 2018, the Supreme Court said no: your phone’s location history paints such a complete picture of your life that the government generally needs a warrant to get it — even though a company holds the data. Chief Justice Roberts compared the records to an ankle monitor you never knew you were wearing. Carpenter is the case that dragged the Fourth Amendment into the smartphone age’s hardest question: who your data protects when someone else stores it.
Decided
June 22, 2018
Vote
5–4
Opinion by
Chief Justice Roberts
Protects
Your location history
The Story Behind Carpenter v. United States
It started with robberies of, of all things, phone stores — and ended with the biggest digital privacy ruling of its generation.2010–2011A crew robs a series of Radio Shack and T-Mobile stores around Detroit and into Ohio — stealing, ironically, smartphones. Police arrest four men; one confesses and hands over phone numbers of alleged accomplices, including Timothy Carpenter’s.
THE REQUESTProsecutors don’t seek a warrant. Under the Stored Communications Act, they get court orders on a lower standard — “reasonable grounds” that records are relevant — and serve them on Carpenter’s wireless carriers, asking for his cell-site location informationCell-site location information (CSLI): the record of which cell towers your phone connected to and when — generated automatically, constantly, just by your phone being on. A time-stamped map of where you’ve been..
THE MAPThe carriers produce 127 days of records — 12,898 location points, an average of 101 per day. The data places Carpenter’s phone near four robberies at the right times. At trial it’s the connective tissue of the case; he’s convicted and sentenced to more than 100 years, driven by mandatory gun-charge stacking.
THE APPEALCarpenter argues the location dragnet was a Fourth Amendment search requiring a warrant. The government answers with the third-party doctrineThird-party doctrine: the old rule that information you voluntarily share with a company — dialed numbers, bank records — loses Fourth Amendment protection. The doctrine Carpenter refused to extend to location history.: the records belong to the phone companies, and data shared with a company gets no protection. The Sixth Circuit agrees with the government. The Supreme Court takes the case.
JUN 22, 2018The Court rules for Carpenter, 5–4. Accessing a week or more of historical cell-site records is a search, and the government generally needs a warrant. The third-party doctrine, born in the era of rotary phones and bank slips, does not stretch to a technology that tracks nearly every American nearly all the time.
The Question the Court Faced in Carpenter v. United States
Two eras of law collided. Old rule one: you have no protected privacy in your public movements — anyone could have watched you drive by. Old rule two: records you share with a company aren’t “yours” to protect. Put together, they seemed to say location records held by carriers were fair game without a warrant. But a phone isn’t a bank slip — it logs your location around the clock, for years, retroactively, for practically everyone. The question: do the old rules follow the data into the smartphone age, or does perfect, effortless, retrospective tracking of a person’s whole life change the constitutional answer?
What the Court Decided in Carpenter v. United States
The data changed the answer — and Roberts explained why in the opinion’s most quoted lines:“As with GPS information, the time-stamped data provides an intimate window into a person’s life, revealing not only his particular movements, but through them his familial, political, professional, religious, and sexual associations.”— Chief Justice Roberts, for the Court
The majority held that people keep a reasonable expectation of privacy in “the whole of their physical movements.” Cell-site records defeat that privacy in a way no human surveillance ever could: they’re detailed, encyclopedic, and effortlessly compiled — and retrospective, letting the government rewind anyone’s life without ever having tailed them. Nor is the “sharing” voluntary in any meaningful sense: your phone reports to towers automatically, and opting out means opting out of modern life.
“When the Government tracks the location of a cell phone it achieves near perfect surveillance, as if it had attached an ankle monitor to the phone’s user.”— on why old precedents didn’t fit
So: obtaining seven days or more of historical CSLI is a search, and the government must generally get a warrant supported by probable cause — the lower Stored Communications Act order isn’t enough. Roberts stressed the ruling is narrow: it didn’t disturb ordinary subpoenas for business records, didn’t decide real-time tracking or “tower dumps,” and left emergencies (kidnappings, bomb threats) covered by the usual exigency exception. All four dissenters wrote separately — Kennedy and Alito warning the decision scrambled settled records law, Thomas and Gorsuch arguing the whole “expectation of privacy” framework was the real problem — a 5–4 split whose aftershocks courts are still working through.
What Carpenter v. United States Means for You
✓ BECAUSE OF CARPENTER
- Police generally need a warrant — real probable cause, a judge’s signature — for your historical location records
- “A company holds the data” is no longer a magic key to your digital life
- The Constitution now recognizes privacy in the whole of your movements — the pattern, not just single moments
- Its logic powers today’s fights over location data of every kind, far beyond cell towers
✗ CARPENTER DOESN’T MEAN
- Your location is invisible — with a warrant, police get it; in genuine emergencies, they can move without one
- Real-time tracking and tower dumps were decided — the Court expressly left those open
- All records you share are now protected — bank, subscriber, and ordinary business records still follow the old rules
- Apps are covered — Carpenter itself was about cell-site records; it took Chatrie (2026) to reach Google location history, and data brokers are still an open fight
- Carpenter went free — courts upheld his conviction anyway under the good-faith exception; the rule protects everyone after him
Questions People Ask About Carpenter v. United States
What exactly is cell-site location information?
The automatic log of which towers your phone talks to. Every call, text, and background app refresh connects you to nearby towers, and carriers time-stamp those connections — historically for years. Tower data used to place you only within a wide wedge of a city; as towers multiplied and small cells arrived, the map has grown sharper and sharper, which only strengthens Carpenter’s logic over time.
Did Timothy Carpenter get out of prison?
No — and it’s the classic Supreme Court ending, the same one Ernesto Miranda got. On remand, courts applied the good-faith exceptionGood-faith exception: evidence isn’t suppressed when officers reasonably relied on the law as it stood at the time. The FBI followed the Stored Communications Act as written in 2011 — so the records stayed in.: agents had followed the statute as it existed, so the evidence stood and his conviction held. He lost his case and won the rule — every location request after June 2018 lives under the warrant requirement he created.
Can police track my phone in real time?
Carpenter deliberately left that open — it covered historical records only. In practice, most agencies now seek warrants for real-time tracking too, many states require them by statute, and courts extending Carpenter’s logic keep pushing that direction. True emergencies are different: carriers can and do provide live location to find a kidnapping victim or a suicidal person, under the standard emergency exception no one disputes.
What about Google location history and geofence warrants?
The sequel litigation. A geofence warrantGeofence warrant: a request compelling a company to identify every device present in a drawn area during a time window — searching an area’s people rather than a named suspect. flips normal investigation: instead of “where was this suspect,” it asks “who was near this crime.” In June 2026 the Supreme Court held in Chatrie v. United States that getting this data is a search. Google has changed how it stores location data, and whether a geofence warrant can ever be valid is the most active Carpenter-descended battlefield right now. The other one: governments buying location data from brokers instead of demanding it — a loophole Congress keeps debating.
Is there a “less than seven days” loophole?
The opinion drew its line at accessing seven days or more, and pointedly declined to say whether a shorter period escapes the warrant rule — so yes, that gray zone exists on paper. In practice, prosecutors mostly just get warrants rather than gamble a conviction on it, and some states have closed the gap by statute. In 2026 the Court narrowed that gap in Chatrie v. United States, which treated a short window of Google location data as a search; how the seven-day line applies to carrier records is still not fully settled.
How does Carpenter fit with Riley?
They’re the two pillars of digital privacy, both written by Roberts. Riley (2014) protects the data inside your phone — police need a warrant to search it, even after arrest. Carpenter protects the data your phone sheds — the location trail held by companies. Read together, their message is the one courts now apply everywhere: the scale of digital data changes the constitutional math, and pre-smartphone rules don’t transfer automatically.
Key Terms in Carpenter v. United States, Explained
Cell-site location information (CSLI) — the tower-connection log that maps your phone’s movements over time.
Third-party doctrine — the old rule that data shared with companies loses protection; Carpenter refused to extend it to location history.
Stored Communications Act order — the lower-standard court order the FBI used; no longer enough for a week-plus of location data.
Probable cause / warrant — the full standard the government must now generally meet for historical CSLI.
Exigent circumstances — genuine emergencies where police may act without a warrant; Carpenter left this untouched.
Good-faith exception — why Carpenter’s own conviction survived: agents reasonably followed the law as it stood.
Geofence warrant — the post-Carpenter frontier: demanding every device present near a crime scene. Ruled a search by the Supreme Court in Chatrie (2026).
Cases Connected to Carpenter v. United States
Riley v. California (2014)The other pillar: a warrant to search your phone’s contents. Riley guards what’s on the phone; Carpenter guards where the phone has been.Read the full case → New Jersey v. T.L.O. (1985)The other place your privacy meets an institution’s power: the school search standard — and the case courts weigh against Riley and Carpenter when schools reach for student phones.Read the full case → Katz v. United States (1967)The foundation Carpenter builds on: the Fourth Amendment protects people, not places — privacy follows reasonable expectations, not property lines.Read the full case → United States v. Jones (2012)The warm-up: a GPS tracker on a car was a search, and five justices signaled that long-term location monitoring troubled them. Carpenter finished the thought.Read the full case →What’s Still Undecided After Carpenter v. United States
Carpenter opened more questions than it closed — deliberately. As of October 2026:
- Geofence and reverse warrants — in Chatrie v. United States (June 2026) the Supreme Court held that getting a person’s location data from Google through a geofence warrant is a Fourth Amendment search. Still open: whether a geofence warrant can ever be specific enough to be valid, and how the ruling applies to keyword-search warrants.
- The data-broker loophole — agencies buying commercially available location data instead of compelling it sits outside Carpenter’s holding; Congress keeps debating bills to close it.
- Real-time tracking and short periods — the questions the Court explicitly reserved are still being answered one circuit and one state statute at a time.
- Everything else your life sheds — smart homes, cars, wearables, and AI assistants all generate Carpenter-shaped records; each is a future case.
Why this page exists: Carpenter is the case standing between your location history and a records request — and it’s barely eight years old, still being fought over, and almost never explained outside law reviews. This page is written for the person carrying the phone. Every fact above comes from the Court’s own opinion — linked below so you can check us.
The Bottom Line on Carpenter v. United States
A phone-store robbery crew, a 127-day map, and a 5–4 Court produced the modern rule of digital privacy: the government can’t rewind your life just because a company kept the tape. Your movements as a whole are yours, a warrant is the price of the map, and the old “you shared it, you lost it” doctrine finally met a technology it couldn’t swallow. The fights Carpenter started — geofences, data brokers, everything your devices remember — will define the next decade of privacy law. Now you know.Your practical guideCan police track your phone? → The other pillarRiley v. California → More casesBrowse all court case files →
Sources
Primary sources:- Carpenter v. United States, 585 U.S. 296 (2018) — full opinion — supreme.justia.com
- Chatrie v. United States, No. 25-112 (2026) — supreme.justia.com
- Carpenter v. United States — argument audio and case summary — oyez.org
- Slip opinion (PDF) — supremecourt.gov
LawJustic is for educational purposes only and does not provide legal advice. Digital privacy law is actively developing and varies by state. If you need help with a specific legal issue, contact a licensed attorney.