GPS Trackers & Electronic Location Tracking in Law Enforcement
How police use GPS and other electronic tracking devices, when attaching or monitoring a tracker becomes a Fourth Amendment search, how United States v. Jones changed the legal framework, and why modern location surveillance increasingly extends beyond a device physically attached to a vehicle.
What this explainer does
Electronic tracking allows investigators to determine where a person, vehicle, package, or other movable object travels without maintaining continuous physical surveillance. The classic police application is a small GPS device covertly attached to a vehicle. But modern tracking can also involve radio-frequency beacons, cellular transmitters, stolen-device location services, factory-installed systems, and location information generated by phones or connected vehicles.
The constitutional analysis depends heavily on how the location information is obtained. A government-installed tracker creates a different Fourth Amendment issue from location information supplied with an owner's consent, and both differ from records compelled from a technology company.
The practical rule is straightforward: when investigators intend to covertly install and use a tracking device on property in which a target has a protected possessory interest, a properly supported warrant should ordinarily be the starting point—not an after-the-fact argument over whether warrantless tracking might have been reasonable.
The law of location surveillance now extends well beyond the physical GPS tracker at issue in Jones. Carpenter v. United States recognized Fourth Amendment protection for historical cell-site location information, and in June 2026 the Supreme Court held in Chatrie v. United States that police acquisition of Google Location History is also a Fourth Amendment search.
The result is a location-privacy framework built from property rights, reasonable expectations of privacy, the sensitivity of aggregated movement data, consent, third-party records, and the particular method used to obtain the information.
1. Overview
GPS tracking converts movement into time-stamped location data that can be viewed, stored, mapped, compared with other evidence, and analyzed over time.
A traditional covert GPS tracker typically contains a location receiver and a method for transmitting or later retrieving recorded coordinates. Depending on the model, investigators may receive near-real-time location updates or download historical movement data after recovering the device.
The operational attraction is obvious. A tracker can help officers maintain surveillance when visual contact is lost, identify recurring destinations, establish travel patterns, corroborate informant information, locate a vehicle during an enforcement operation, and direct physical surveillance more efficiently.
The constitutional problem is equally obvious. Electronic tracking can create a durable, searchable record of movements that would have required extensive personnel and resources to reproduce through conventional surveillance.
2. How Electronic Tracking Works
GPS determines location
A GPS receiver calculates location using timing information transmitted by navigation satellites. A law-enforcement tracker can pair that location capability with cellular, radio, satellite, or other communications technology so the location can be transmitted to investigators.
The tracker does not necessarily need to transmit continuously
Some devices report location in near real time. Others store coordinates internally for later retrieval. Reporting intervals, power-management settings, signal availability, environmental conditions, and device configuration can affect the completeness and precision of the resulting record.
Location is evidence—not infallible ground truth
A coordinate ordinarily shows where the tracker was located, not necessarily who was driving the vehicle, who possessed the tracked object, or what occurred at the location. Investigators should preserve the distinction between device location and conclusions about a particular person's presence or conduct.
3. Different Forms of Electronic Location Tracking
Officers physically attach a device to a vehicle or other property and use it to monitor movement. This is the paradigm addressed in United States v. Jones.
Earlier tracking systems emitted a signal that officers followed with receiving equipment. Knotts and Karo established important pre-GPS principles.
A victim or owner may use a phone, vehicle, tag, or account-based service to locate stolen property and share that information with police.
Connected vehicles may generate location or telematics information without police physically installing a tracker. Access raises separate provider, privacy, process, and scope questions.
CSLI and app-based location histories can reveal movements without physical attachment of a police device. Carpenter and Chatrie are central here.
Consumer finding devices can reveal the location of property through a network of nearby devices. Police involvement can range from receiving victim-generated data to obtaining provider records or deploying the technology themselves.
4. A Typical GPS-Tracking Investigation
5. Before GPS: United States v. Knotts and United States v. Karo
The Supreme Court's electronic-tracking doctrine began with radio beepers decades before modern GPS made continuous tracking cheap and precise.
United States v. Knotts — tracking movements exposed to public view
In United States v. Knotts, 460 U.S. 276 (1983), officers used a beeper placed in a container to help follow a vehicle over public roads. The Court held that the monitoring at issue did not violate a legitimate expectation of privacy because the beeper principally augmented visual surveillance of movements exposed on public thoroughfares.
But Knotts expressly recognized that a different constitutional issue could arise from more pervasive surveillance. That reservation became increasingly important as tracking technology moved from intermittent radio signals to continuous digital location records.
United States v. Karo — tracking into a private residence
In United States v. Karo, 468 U.S. 705 (1984), the Court held that monitoring a beeper while it was inside a private residence invaded a protected privacy interest when the monitoring revealed information that could not have been obtained through observation from outside the protected area.
6. United States v. Jones: Physical Installation Is a Fourth Amendment Search
United States v. Jones, 565 U.S. 400 (2012), changed the legal landscape for government-installed GPS tracking devices.
Investigators obtained a warrant authorizing installation of a GPS device on a Jeep within the District of Columbia and within ten days. Agents installed the device on the eleventh day while the vehicle was in Maryland, outside the warrant's authorization, and then tracked the vehicle for 28 days.
The Supreme Court held that the government's attachment of the GPS device to the vehicle and use of that device to obtain information constituted a Fourth Amendment search. The majority relied on a property-based rationale: officers physically occupied an "effect" protected by the Fourth Amendment for the purpose of obtaining information.
The concurrences matter
Justice Sotomayor agreed with the property-based holding but emphasized that GPS can create a precise and comprehensive record of public movements and can reveal sensitive associations. Justice Alito, joined by three other Justices, would have analyzed the case under reasonable expectations of privacy and concluded that long-term GPS monitoring of the vehicle crossed the constitutional line.
Those concurrences helped frame the later development of digital-location privacy in Carpenter and, most recently, Chatrie.
7. Does Police GPS Tracking Require a Warrant?
For routine investigative planning, agencies should distinguish the narrow holding of Jones from the safer operational rule.
Government attachment and use of a GPS device on protected property for the purpose of obtaining information is a Fourth Amendment search.
The Court did not decide whether every warrantless GPS search is necessarily unreasonable or whether a recognized exception could justify a particular warrantless use.
When feasible, obtain a probable-cause warrant that expressly authorizes installation, monitoring, duration, entry or access needed for installation, and removal.
A warrant also gives investigators a defined legal record addressing the target property, probable cause, duration, geographic or jurisdictional issues, method of installation, monitoring, return, and notice. That structure becomes especially important when the tracker remains deployed for days or weeks.
8. Duration, Aggregation, and the Mosaic Problem
Location surveillance becomes more revealing as individual points accumulate into a pattern.
A single observation may reveal little. A month of movement data may reveal a home, workplace, associates, medical visits, religious attendance, political activity, intimate relationships, travel routines, and recurring locations. This aggregation concern is often described as the mosaic theory: the whole can reveal substantially more than the individual observations considered separately.
The Jones majority did not adopt a duration threshold for non-trespassory tracking. The concurring opinions, however, focused heavily on prolonged monitoring. Later, Carpenter relied on the privacy interest in the whole of a person's physical movements when addressing historical CSLI.
9. From Jones to Carpenter and Chatrie
Modern location surveillance often requires no physical device installed by police. That development makes the reasonable-expectation-of-privacy line of cases increasingly important.
Carpenter v. United States — historical cell-site location information
In Carpenter v. United States, 585 U.S. 296 (2018), the Supreme Court held that government acquisition of the historical cell-site location records at issue was a Fourth Amendment search and that the government generally must obtain a warrant supported by probable cause before obtaining such records. The Court emphasized the detailed, retrospective, and efficiently compiled record of physical movements.
Chatrie v. United States — Google Location History
On June 29, 2026, the Supreme Court decided Chatrie v. United States, No. 25-112. Police investigating a bank robbery used a geofence warrant directed to Google Location History. The Court held that police conducted a Fourth Amendment search when they acquired the petitioner's location information from Google.
The Court rejected the argument that only lengthy tracking triggers Fourth Amendment protection for this form of location data. It emphasized that even short-term location information can reveal sensitive details and held that the fact the data was held by a third-party technology company did not eliminate the user's reasonable expectation of privacy.
The Court did not decide whether the particular multi-step geofence warrant was constitutionally reasonable. It remanded that probable-cause and particularity question for further consideration.
10. Consent, Stolen Property, and Owner-Generated Tracking
Not every police use of electronic location information involves covert government installation of a tracking device.
A theft victim may activate a phone-finding service, vehicle-recovery system, or consumer tracker and provide the resulting location to officers. In that setting, the government's role, the consenting person's authority over the tracked property or account, and the suspect's asserted privacy or possessory interest may differ substantially from Jones.
In People v. Barnes, 216 Cal. App. 4th 1508 (2013), California officers used location information from a stolen smartphone with the owner's consent as part of the circumstances leading to a detention. The Court of Appeal rejected the defendant's Fourth Amendment challenge on the facts presented.
11. Federal Tracking-Device Procedure
Federal law provides a specific procedural structure for mobile tracking devices.
18 U.S.C. § 3117
Section 3117 defines a tracking device as an electronic or mechanical device that permits tracking the movement of a person or object. When a court is empowered to issue an order for installation of a mobile tracking device, the order may authorize use inside and outside the court's jurisdiction if the device is installed within that jurisdiction.
Federal Rule of Criminal Procedure 41
Rule 41 expressly addresses tracking-device warrants. A federal tracking-device warrant must identify the person or property to be tracked and specify a reasonable period of use. The initial period may not exceed 45 days, with additional extensions of up to 45 days each for good cause.
Rule 41 also generally requires installation authorized by the warrant to occur within 10 days, requires the officer to record the installation time and period of use, and requires return of the warrant within 10 days after tracking ends. The rule contains notice provisions and permits delayed notice when legally authorized.
| Federal Rule 41 Issue | General Tracking-Device Requirement | Why It Matters |
|---|---|---|
| Probable cause | Judge issues the warrant when probable cause supports installation and use | Connects the tracking to a defined investigative and evidentiary basis. |
| Installation period | Specified period not longer than 10 days | Prevents stale authorization for installation. |
| Use period | Reasonable period, initially no longer than 45 days | Prevents open-ended monitoring. |
| Extensions | Reasonable extensions of up to 45 days each for good cause | Requires renewed judicial oversight for continued tracking. |
| Return | Generally within 10 days after use ends | Creates a record of execution and duration. |
| Notice | Copy generally served after tracking; delayed notice may be authorized | Balances covert investigation with post-use judicial process. |
12. California: Penal Code § 637.7
California Penal Code § 637.7 generally prohibits use of an electronic tracking device to determine the location or movement of a person. The statute defines an electronic tracking device as a device attached to a vehicle or other movable thing that reveals its location or movement through transmitted electronic signals.
The statute contains exceptions, including consent by the registered owner, lessor, or lessee of a vehicle and the lawful use of an electronic tracking device by a law-enforcement agency.
California agencies should also distinguish § 637.7's definition—focused on a device attached to a vehicle or other movable thing—from location information obtained through providers, phones, connected vehicles, ALPR systems, or other sources governed by different legal rules.
13. Operational Issues Beyond the Warrant
A warrant authorizing tracking does not excuse an unauthorized entry onto protected property. Plan where and how installation and removal will occur.
Confirm identifiers before installation. A tracker placed on the wrong vehicle creates investigative, privacy, evidence, and potential liability problems.
Maintenance or battery replacement may require additional physical access and should remain within the authorization granted.
The target may travel across counties, states, tribal lands, international borders, or other jurisdictions. Resolve legal and coordination issues before deployment.
Exigent circumstances may raise a different warrant analysis, but the emergency and its duration should be specifically documented rather than treated as a generic exception.
Agencies need a procedure to stop monitoring, recover or disable the device, preserve the data, complete returns, and obtain extensions before authorization expires.
14. Tracking Data as Digital Evidence
A tracker creates both investigative intelligence and potentially discoverable evidence.
| Record | Potential Evidentiary Significance | Agency Control |
|---|---|---|
| Raw coordinate data | Underlying time-stamped location points | Preserve the original export or native data when feasible. |
| Map visualization | Human-readable presentation of movement patterns | Do not treat a derivative map as a substitute for raw data. |
| Device identifier | Links the dataset to the physical tracker deployed | Document serial number, model, assignment, and configuration. |
| Installation / removal record | Establishes when and where the device was physically deployed | Document personnel, dates, times, target identifiers, and significant access. |
| System audit log | May show user access, queries, exports, configuration, or changes | Retain according to evidence, discovery, and records rules. |
| Surveillance corroboration | Can connect a coordinate to a particular driver, event, meeting, or location | Preserve reports, photographs, BWC, video, and related records. |
15. Governance Framework for Agency Tracking Programs
Identify which investigations, threats, stolen-property events, or other circumstances justify agency use of tracking technology.
Establish when a warrant is required, who reviews applications, what exceptions may be used, and how emergency deployments are documented.
Specify who may install, maintain, remove, or recover devices and what documentation is required for each event.
Tie monitoring to the judicial authorization and require documented extensions before tracking continues beyond the approved period.
Limit live and historical location data to personnel with a legitimate investigative, supervisory, legal, evidence, or auditing purpose.
Maintain records showing who accessed a tracking platform, what data was viewed or exported, and whether configurations were changed.
Address cloud storage, encryption, retention, cybersecurity, account termination, subcontractors, support access, and data portability.
Determine how raw data, maps, audit logs, applications, returns, reports, and related communications are preserved and produced when legally required.
Reassess policy as appellate decisions, state statutes, provider practices, connected vehicles, and consumer tracking systems evolve.
16. Questions Every Agency Should Answer
17. What Comes Next
Police will increasingly encounter location information generated by vehicles themselves, reducing the need to physically attach a separate tracker.
Small Bluetooth finding devices and crowdsourced location networks blur the line between victim-generated information and government surveillance.
Chatrie makes clear that highly revealing digital location information cannot be treated as constitutionally insignificant merely because police seek a short period.
GPS, ALPR, CSLI, vehicle telematics, cameras, transaction records, and app data can be combined into a much richer movement profile than any source provides alone.
Software can identify recurring destinations, co-travel, dwell time, route deviations, and other patterns, raising new questions about inference and automated suspicion.
State constitutions and statutes may impose rules beyond the federal constitutional floor, particularly for location records and surveillance technologies.
18. Key Terms
19. Related ShieldPST.ai Resources
Examine historical and real-time cellular location information, warrants, provider data, and Carpenter.
Open explainer →Review reverse-location searches, probable cause, particularity, and the Supreme Court's 2026 Chatrie decision.
Open explainer →Compare device-based tracking with camera-generated vehicle-location records and networked plate searches.
Open explainer →Explore commercially collected location information and government access to third-party data.
Open explainer →Connect tracking technology to Fourth Amendment doctrine, privacy, evidence, procurement, policy, and oversight.
Open resource →Return to the Shield Technology Reference Library.
Browse explainers →20. Selected Authoritative and Primary Sources
Holding that the government's attachment of a GPS device to a vehicle and use of that device to monitor movement constituted a Fourth Amendment search.
Review Jones
Beeper-tracking decision addressing electronic augmentation of surveillance of vehicle movements exposed on public roads.
Review Knotts
Holding that warrantless monitoring of a beeper inside a private residence can violate the Fourth Amendment when it reveals information unavailable through observation outside the home.
Review Karo
Landmark decision holding that acquisition of the historical CSLI at issue was a Fourth Amendment search and generally required a probable-cause warrant.
Review Carpenter
Holding that police acquisition of Google Location History was a Fourth Amendment search; the Court remanded the reasonableness of the multi-step geofence warrant for further review.
Review Chatrie
Federal procedures for tracking-device warrants, including installation, duration, extensions, returns, and notice.
Review Rule 41
Federal statutory definition of a tracking device and authority concerning use across jurisdictional boundaries after authorized installation.
Review § 3117
California statute addressing use of electronic tracking devices, owner consent, and lawful law-enforcement use.
Review California statute
California decision addressing police use of GPS information from a stolen smartphone with the owner's consent as part of the basis for detention.
Review Barnes
21. Key Takeaways
- GPS and other tracking technologies allow investigators to convert physical movement into time-stamped, searchable location evidence.
- In United States v. Jones, physically attaching a GPS device to a protected vehicle and using it to obtain information constituted a Fourth Amendment search.
- Jones should not be overstated: the Supreme Court did not decide that no recognized exception could ever justify a warrantless GPS search.
- As an operational matter, a probable-cause warrant is ordinarily the sound starting point for planned government installation and monitoring of a covert tracker.
- Knotts and Karo remain important for understanding the difference between following publicly exposed movement and using technology to reveal information from protected spaces.
- Duration and aggregation matter because a movement history can reveal associations and patterns that no isolated observation reveals.
- There is no universal Supreme Court rule making 7 days, 28 days, or another specific duration the dividing line for every form of tracking.
- Carpenter extended location-privacy analysis to historical CSLI even though the records were held by a third party.
- In June 2026, Chatrie held that police acquisition of Google Location History is a Fourth Amendment search and rejected the idea that a short time window automatically eliminates the protected privacy interest.
- Owner-consented tracking of stolen property presents a materially different factual setting from covert government attachment of a tracker.
- Federal Rule 41 contains detailed tracking-device procedures, including installation and monitoring periods, returns, and notice.
- California Penal Code § 637.7 permits lawful law-enforcement use but does not eliminate constitutional or other legal requirements that determine whether the use is lawful.
- Tracking data must be treated as digital evidence: preserve raw data, device identifiers, installation records, audit logs, maps, and corroborating surveillance.
- The next major tracking questions will increasingly involve connected vehicles, provider-held location information, consumer tracking networks, and fusion of multiple location datasets rather than a magnet-mounted GPS box alone.