The Issue
In Chatrie v. United States, the Supreme Court will decide a critical question for the digital age: whether law enforcement can use “geofence warrants” to obtain the identities of cell phone users present in a specific location at a specific time without violating the Fourth Amendment. These warrants—which cast a dragnet across an area and identify everyone whose phone pinged cell towers there—represent a novel and troubling erosion of privacy rights. As courts and police agencies increasingly rely on geofence technology, the Supreme Court’s answer will shape criminal defense strategy for years to come.
Background
Geofence warrants work by asking Google, Apple, and other tech companies to identify all cell phone users whose devices were in a defined geographic area during a specified time window. Rather than targeting a specific suspect, these warrants cast a wide net—sometimes capturing hundreds or thousands of individuals—to identify anyone who happened to be near a crime scene. Law enforcement then narrows the suspect pool after learning who was there. The practice has exploded in recent years: federal agencies used geofence warrants fewer than ten times before 2015, but Google alone reported responding to more than 200,000 geofence requests in 2021.
The Fourth Amendment protects against “unreasonable searches and seizures.” Traditionally, courts required law enforcement to establish probable cause and describe the specific person or place to be searched before issuing a warrant. Geofence warrants invert this logic: they identify people based solely on their location, without individualized suspicion. A defendant might be swept up in the geofence net simply for being in the wrong place at the right time. The Ninth Circuit Court of Appeals held such warrants constitutional in a preliminary ruling, concluding they were not so overbroad as to violate the Fourth Amendment. That decision prompted the Supreme Court to grant certiorari in Chatrie.
Strategic Implications
If the Supreme Court upholds geofence warrants, criminal defense practice will face a seismic shift. Defendants will face a new evidentiary obstacle: proximity to the crime scene. The combination of geofence data and cell-site location information (CSLI) could transform investigations, particularly in urban areas where cell towers densely cover wide spaces. Defense counsel will need to develop sophisticated challenges to geofence evidence, including arguments about location accuracy, tower geometry, and the frequent nature of the initial warrant.
Conversely, if the Supreme Court restricts or prohibits geofence warrants, it will represent a significant victory for Fourth Amendment privacy in the technological context. The decision could throw law enforcement to rely on more traditional, investigative methods and return to individualized suspicion as the predicate for surveillance. For defendants, such a ruling would shield them from the systematic identification that geofence warrants enable. Either way, the ruling will redefine the scope of privacy rights in an era when our cell phones track our movements in real time.
How Does This Apply in Louisiana?
Louisiana criminal procedure is governed by La. C.Cr.P. art. 215.1 (post-conviction relief) and the broader Fourth Amendment framework. The Louisiana Constitution Article 1, Section 5 also protects against unreasonable searches. Geofence warrants have not yet become prevalent in Louisiana practice, but this is changing as federal enforcement agencies and state law enforcement adopt the technology.
If the Supreme Court approves geofence warrants, Louisiana defense counsel should expect prosecutors to begin using them in federal cases and, potentially, in state prosecutions involving multi-agency task forces. La. R.S. 15:510 et seq. (discovery) would require the state to disclose geofence data and the underlying warrant to the defense. However, many defense attorneys lack familiarity with the technical aspects of geofence evidence, including the accuracy margins, privacy implications, and limitations of cell-tower location data.
Defense strategy should include: (1) challenging the scope and breadth of the geofence warrant itself under the Fourth Amendment; (2) requesting detailed forensic analysis of the location data, including margin of error; (3) exploring alternative explanations for the defendant’s presence in the geofence zone; and (4) cross-examining law enforcement and tech company representatives on the reliability and limitations of the technology. Given the stakes—a single geofence result can place a defendant at or near a crime scene—defense counsel must develop sophisticated technical and constitutional objections now, before such warrants become routine.
Frequently Asked Questions
What is a geofence warrant?
A geofence warrant is a court order authorizing law enforcement to request from tech companies (like Google and Apple) the identities of all cell phone users whose devices were in a specific geographic area during a specific time window. It is a reverse search that identifies people by their location rather than targeting a specific suspect.
How accurate are geofence results?
Accuracy varies significantly depending on cell tower density, building materials, and device type. In urban areas with dense tower coverage, accuracy can be within 100–200 meters. In rural areas, accuracy can degrade to 500 meters or more. Defense counsel should always demand detailed forensic analysis of accuracy margins.
Is using a geofence warrant a violation of the Fourth Amendment?
The Supreme Court in Chatrie will decide this question. Currently, the Ninth Circuit upheld geofence warrants as constitutional, but other circuits and state courts have raised concerns about their overbreadth and lack of individualized suspicion.
What discovery am I entitled to if the state uses a geofence warrant?
You are entitled to the geofence warrant itself, the affidavit supporting the warrant, all location data identifying you, and documentation of the methodology used to obtain the data. You should also demand technical specifications of cell towers and margin of error analysis.
Can geofence evidence place me at a crime scene even if I was not there?
Yes. Geofence results can be inaccurate due to tower geometry, device type, or signal reflection. Additionally, a cell phone is not always carried by its owner. Defense counsel should investigate whether the defendant actually possessed the phone and whether location data contradicts other evidence.