United States v. Jones
The Court ruled that police conducted a Fourth Amendment "search" when they physically attached a GPS tracking device to a suspect's car and used it to monitor his movements for four weeks without a valid warrant.
Rather than deciding the case solely on whether the suspect had a reasonable expectation of privacy, the Court revived an older property-based test: physically placing a device on someone's belongings to gather information is a search in itself, regardless of privacy expectations. The ruling leaves open how the Fourth Amendment applies to newer surveillance methods that don't involve physically touching a person's property.
“The Government physically occupied private property for the purpose of obtaining information.”
The core reasoning for why attaching the GPS device was a Fourth Amendment search.
How it got here: A federal district court convicted Jones after partially admitting the GPS evidence; the D.C. Circuit reversed, finding the warrantless GPS tracking unconstitutional, and the government sought Supreme Court review.
The Case in Depth
What happened
Antoine Jones owned a nightclub in Washington, D.C. and became the target of a federal-local drug trafficking investigation. Officers obtained a warrant to place a GPS tracker on a Jeep registered to Jones's wife but installed it a day late and in the wrong jurisdiction. They then tracked the vehicle's movements around the clock for 28 days, gathering location data that helped convict Jones of conspiring to distribute cocaine.
The question before the Court
Did police need a warrant before secretly attaching a GPS tracker to a suspected drug dealer's Jeep and using it to record his every move for four weeks?
The Court's answer
No — police needed a warrant. The Court ruled that physically attaching a GPS device to Jones's Jeep and using it to track his movements for four weeks was a Fourth Amendment "search," because the government physically intruded on his property specifically to gather information. That kind of intrusion on a person's belongings has always counted as a search, independent of whether Jones also had a reasonable expectation of privacy in his public movements.
Because the physical trespass alone was enough to answer the question, the Court didn't need to decide the harder issue of whether purely electronic tracking, without touching anyone's property, would also require a warrant. That question — increasingly important given smartphones and built-in vehicle trackers — was left for another day.
Curious how the Court got there? See the step-by-step legal reasoning →
Why it matters
Police nationwide now know that physically installing a tracking device on a car or other personal property, even briefly, generally requires a warrant. The decision doesn't resolve whether tracking someone through their phone or a factory-installed GPS system (without physically placing anything) also counts as a search, so that question remains unsettled for future surveillance technology.
What changes now
This is a final merits ruling, not a temporary order. The judgment affirms the D.C. Circuit's reversal of Jones's conviction, meaning the GPS evidence cannot be used against him without a valid warrant. The decision leaves open how the Fourth Amendment applies to tracking methods that don't involve physically touching a person's property, an issue the concurring justices flagged as increasingly important given smartphones and factory-installed tracking systems.
What this does not decide
The Court expressly did not decide whether tracking someone's movements through means that don't involve a physical intrusion — like GPS-enabled smartphones or built-in vehicle tracking systems — would also count as a search, or whether the GPS search here would have been reasonable if the government had raised that argument below.
Concurrences and dissents
Concurrence — Justice Sotomayor
Justice Sotomayor joined the majority's trespass-based holding but wrote separately to argue that even without a physical intrusion, long-term GPS monitoring likely violates reasonable privacy expectations because it can reveal a detailed record of a person's associations and habits. She also questioned whether information voluntarily given to third parties like phone or internet companies should always lose Fourth Amendment protection.
Concurrence — Justice Alito
Justice Alito agreed the four weeks of GPS tracking was a search but rejected the majority's property-trespass reasoning as artificial and poorly suited to modern surveillance. He would have decided the case entirely under the Katz reasonable-expectation-of-privacy test, concluding that while short-term public monitoring is fine, long-term GPS tracking crosses into a search because society doesn't expect every movement to be catalogued for weeks.
How the Court got there
The legal reasoning, step by step
- The Court asked whether physically placing a device on someone's property to gather information was understood as a 'search' when the Fourth Amendment was adopted, focusing on the Amendment's text protecting 'persons, houses, papers, and effects.'
- The Court traced its own history, noting that Fourth Amendment law was tied to common-law trespass doctrine until the mid-20th century, when Katz v. United States introduced a separate test asking whether the government violated a person's reasonable expectation of privacy.
- The Court held that the Katz privacy test was added on top of the older trespass test, not a replacement for it, so a physical intrusion onto someone's property to gather information remains an independent basis for finding a search.
- Applying that principle, the Court found that installing the GPS device on the Jeep's undercarriage and using it to track the vehicle was a physical intrusion onto the Jeep, an 'effect' protected by the Fourth Amendment, undertaken specifically to gather information.
- Because a physical trespass for information-gathering purposes was enough to establish a search on its own, the Court did not need to decide whether Jones separately had a reasonable expectation of privacy in his public movements under the Katz test.
Doctrinal impact
Cases affected by this decision
Reaffirms Katz v. United States (389 U. S. 347)
The Court reaffirmed Katz's privacy test but held it supplemented, rather than replaced, the older property-trespass test.
Distinguishes United States v. Knotts (460 U. S. 276)
The Court found this earlier beeper-tracking case did not foreclose finding a search here because it never addressed physical trespass.
Distinguishes United States v. Karo (468 U. S. 705)
The Court distinguished this beeper case because the defendant there never possessed the item before the device was installed.