In most situations, police cannot track your phone without a warrant. The Supreme Court’s 2018 ruling in Carpenter v. United States held that pulling your cell-site location records from a carrier is a Fourth Amendment search, which means officers generally need a warrant backed by probable cause.1Supreme Court of the United States. Carpenter v. United States, 585 U.S. 296 (2018) But the rule has real exceptions, and the answer to whether police can track your phone without a warrant depends on what they are tracking, how they are getting it, and the circumstances at the moment.
The Default Rule: A Warrant Is Required
In Carpenter, the government obtained 127 days of Timothy Carpenter’s cell-site location information from his wireless carrier without a warrant. The Supreme Court said that was a search. Cell-site records provide a detailed chronicle of where a person goes, when they arrive, and how long they stay, and that level of surveillance is exactly the kind of privacy invasion the Fourth Amendment was designed to check.1Supreme Court of the United States. Carpenter v. United States, 585 U.S. 296 (2018)
The Court’s 2014 decision in Riley v. California set a matching rule for the phone itself. When police arrest someone, they can search items on that person without a separate warrant. Phones are the exception. A cell phone contains far more personal information than a wallet or a bag, so officers generally need a warrant before they unlock and search the digital contents of a phone seized during an arrest.2Justia Law. Riley v. California, 573 U.S. 373 (2014) Police can still seize the phone to prevent evidence destruction. They just cannot go through it.
Between Carpenter and Riley, the baseline is clear: your location data and the contents of your phone are protected. A warrant is the norm.
When Police Can Track Without a Warrant
The warrant rule has case-specific exceptions. The Carpenter Court expressly said its ruling does not disturb them.
Exigent Circumstances
When the situation is urgent enough that waiting for a warrant would be unreasonable, officers can act without one. The Court gave concrete examples: bomb threats, active shootings, and child abductions. In those situations, warrantless access to cell-site location information is still permitted.1Supreme Court of the United States. Carpenter v. United States, 585 U.S. 296 (2018)
Consent
If you agree to let police search your phone or access your location, no warrant is needed. Officers do not have to tell you that you can refuse. You can say no, and in most situations that refusal is not evidence of anything. Once you say yes, though, the Fourth Amendment protection is gone.
Voluntary Disclosure by Your Carrier in an Emergency
Federal law lets carriers hand over your data on their own during emergencies, with no court involvement at all. Under 18 U.S.C. ยง 2702, a provider may disclose both the content of communications and customer records to law enforcement if it believes in good faith that an emergency involving danger of death or serious physical injury requires immediate disclosure.3Office of the Law Revision Counsel. 18 U.S. Code 2702 – Voluntary Disclosure of Customer Communications or Records This is the mechanism that lets police get near-instant location data for a missing person or a kidnapping victim.
Metadata Follows a Lower Standard
Not every piece of phone data is treated the same way. The law draws a hard line between the content of your communications and the information about them.
The content of your calls, messages, emails, and voicemails receives the strongest protection. Under the Stored Communications Act, the government generally needs a warrant to compel a provider to disclose the contents of electronic communications in storage for 180 days or less. Older stored content historically allowed lesser process, though many courts and providers now treat all stored content as warrant-protected regardless of age.4Office of the Law Revision Counsel. 18 U.S. Code 2703 – Required Disclosure of Customer Communications or Records
Metadata is different. Numbers you called, numbers that called you, timestamps, and call duration can be captured under the Pen Register and Trap and Trace Statute. To install a pen register or trap and trace device, a government attorney only has to certify that the information is likely to be relevant to an ongoing criminal investigation. That is a much easier bar than probable cause, which is one reason metadata collection is far more common than content wiretaps.5Office of the Law Revision Counsel. 18 U.S. Code 3123 – Issuance of an Order for a Pen Register or Trap and Trace Device The statute also restricts these tools to dialing, routing, addressing, and signaling information. They cannot capture the content of any communication.6Office of the Law Revision Counsel. 18 U.S. Code 3121 – General Prohibition on Pen Register and Trap and Trace Device Use
Real-Time Tracking and Tower Dumps
Whether police want to know where you are right now or where you were last month changes the legal picture. Federal law authorizes courts to issue orders for mobile tracking devices that follow a person’s movements in real time.7Office of the Law Revision Counsel. 18 U.S. Code 3117 – Mobile Tracking Devices Because live surveillance is more intrusive, courts typically require a full probable cause warrant for it.
Carpenter settled the question for historical cell-site records. But the Court deliberately left several related techniques unaddressed: real-time cell-site location information, tower dumps (bulk downloads of every device that connected to a specific tower during a window of time), conventional surveillance tools, and national security collection.1Supreme Court of the United States. Carpenter v. United States, 585 U.S. 296 (2018) The federal trend since Carpenter has been toward requiring warrants for real-time phone tracking, but the standards are not fully uniform.
Cell-Site Simulators
Police also deploy portable devices commonly called Stingrays or IMSI catchers. These simulators mimic legitimate cell towers, tricking nearby phones into connecting to them and revealing location and identifying information. Under a 2015 Department of Justice policy, federal agents generally must obtain a search warrant before using a cell-site simulator, with narrow exceptions for emergencies like active threats to life or the pursuit of a fleeing suspect.8U.S. Department of Justice. DOJ Policy Guidance: Use of Cell-Site Simulator Technology State and local practice varies.
The Data Broker Workaround
There is a route around Carpenter that is not yet fully closed. Federal agencies including the FBI, DEA, and Department of Homeland Security have purchased phone location records from commercial data brokers that aggregate data from smartphone apps. Because the agencies argue this is a commercial transaction rather than a government search, they take the position that Carpenter‘s warrant requirement does not apply. Courts have not yet definitively ruled on whether the practice violates the Fourth Amendment. The Fourth Amendment Is Not For Sale Act, which would prohibit agencies from buying this kind of sensitive data, passed the House in 2024 but stalled in the Senate.9Congress.gov. H.R.4639 – Fourth Amendment Is Not For Sale Act
Phones at the Border
The rules change at international borders and airports. Under the border search exception, customs officers can inspect your belongings without a warrant or probable cause. How far that authority reaches into electronic devices is still being contested.
Current federal policy distinguishes a basic or manual search, where an officer scrolls through your phone by hand, from an advanced or forensic search, where officers use specialized tools to copy and analyze the data. The manual search can be conducted without any individualized suspicion. The forensic search requires reasonable suspicion of a legal violation or a national security concern. Reasonable suspicion is a lower bar than probable cause, but it still needs some articulable basis.
Federal circuits have not agreed on a single standard. Some circuits allow manual searches with no suspicion at all and require reasonable suspicion for forensic searches. Others have questioned whether even a forensic border search should require a warrant. Circuits also differ on what officers can look for: some limit border searches to evidence of border-related crimes like smuggling, others allow searches for a broader range of offenses. Where you cross matters.
Geofence Warrants
Geofence warrants reverse the usual order of an investigation. Instead of identifying a suspect and then seeking their location data, police start with a place and a time, then ask a technology company to identify every device that was inside a geographic radius during that window. The process usually runs in stages: an anonymized list of devices, then expanded location histories for a subset, then the unmasking of individual users. The technique sweeps in data from people who have no connection to the crime.
The Supreme Court granted certiorari in Chatrie v. United States in January 2026, agreeing to decide whether the execution of a geofence warrant violates the Fourth Amendment.10Supreme Court of the United States. Chatrie v. United States – Questions Presented A ruling is expected by mid-2026 and could set the first nationwide standard for this technique. In the meantime, the practical landscape shifted in late 2023 when Google announced it would stop storing location data in its centralized Sensorvault database, moving that history onto users’ devices with encrypted cloud backups. Google had been the primary target of geofence requests. Other companies may still respond to them.
If Your Phone Is Off
Once your phone is fully powered down, it stops transmitting to cell towers, GPS satellites, and Wi-Fi networks. Without those signals, there is no live trace. But the trail is not entirely cold. Your carrier keeps the last location your phone registered before it shut down, and police can get that record with the appropriate legal process. Some modern smartphones also include low-power hardware that broadcasts a short-range Bluetooth signal for a limited time after shutdown, letting nearby devices relay location data back to the manufacturer’s network. Pulling the SIM card ends carrier-based tracking but does not disable those offline-finding features.
Turning your phone off stops most real-time tracking. It does not erase the historical location data your carrier already holds, and it may not immediately silence every signal the device sends.