Cell-Site Location Information: Warrants, Simulators, and Suppression

Cell-site location information is the record your wireless carrier keeps of which towers your phone connected to and when, and since 2018 law enforcement generally needs a search warrant supported by probable cause to obtain it. The Supreme Court set that rule in Carpenter v. United States, but the edges of the doctrine keep moving as courts confront real-time tracking, cell-site simulators, tower dumps, and geofence warrants. What follows is a plain guide to how these records are made, what they actually show, who can access them, and how the evidence can be challenged.

How the Records Are Created

Every cell phone constantly scans for the strongest radio signal from nearby towers. When your phone finds one, it connects through a handshake, and your carrier logs that connection. This happens hundreds of times a day in the background while the phone sits idle, not just when you make a call or send a text. Each entry records the tower ID, the antenna sector that handled the signal, and a timestamp.

Carriers originally kept these logs for billing and network troubleshooting. Over weeks and months, though, the logs build into a detailed timeline of where a device has been. A single day of records might show where you slept, where you work, which doctor’s office you visited, and what route you drove home. That timeline is why the data matters to investigators and why courts have grown wary of easy access to it.

The Warrant Rule for Historical Records

Before 2018, law enforcement could get historical CSLI through a court order under the Stored Communications Act. The standard was low: investigators only had to show “specific and articulable facts” that the records were relevant to an ongoing criminal investigation.¹ No judge had to find probable cause that a crime had occurred.

Carpenter v. United States changed that. The Supreme Court held that people have a reasonable expectation of privacy in the record of their physical movements captured through CSLI, and that the government must generally obtain a warrant supported by probable cause before compelling a carrier to hand over those records.² A Stored Communications Act order is no longer enough.

Carpenter left a gap. The Court said that “accessing seven days of CSLI constitutes a Fourth Amendment search” but declined to decide whether shorter periods could be obtained without a warrant.³ Lower courts have been inconsistent on this point, so in practice most prosecutors get a warrant regardless of the time span to avoid suppression issues later. Records obtained in good-faith reliance on the older statute before Carpenter came down have been allowed at trial in some circuits, but the going-forward rule requires a warrant or a recognized exception.

Real-Time Tracking Is a Separate Question

Real-time tracking means locating a phone as it moves through the network right now, rather than reviewing where it went last month. Law enforcement does this by sending a command to the carrier that triggers an immediate location update, sometimes called pinging the phone.

Carpenter explicitly did not address real-time CSLI.³ The Pen Register and Trap and Trace Statute requires a court order to install tracking devices, but the application standard is low: the government only needs to certify that the information sought is relevant to an ongoing criminal investigation.⁴ That falls well below the probable-cause standard Carpenter set for historical records.

Most federal prosecutors and many state courts now treat real-time CSLI tracking as requiring a full warrant. The reasoning is that if reviewing where someone was last week is a Fourth Amendment search, tracking where they are right now is at least as intrusive. Until the Supreme Court or Congress speaks directly, though, the standard varies by jurisdiction.

Cell-Site Simulators Are Not the Same Thing

A cell-site simulator, often called a Stingray after a popular brand, is a device that mimics a cell tower. Nearby phones connect to it as if it were part of the carrier’s network, revealing their location and identifying information to whoever is operating the device. Unlike a request to a carrier for stored records, this puts the surveillance hardware in law enforcement’s own hands.

Since September 2015, the Department of Justice has required federal agents to obtain a search warrant supported by probable cause before using a cell-site simulator. Under the policy, agents may only use the device to collect a phone’s location and identifying number. Capturing the content of calls, texts, or data is prohibited. Exigent circumstances like an imminent threat to life can justify deployment without a warrant, but agents must still comply with the pen register statute and obtain judicial authorization after the fact.⁵ State and local agencies have their own policies, and not all of them match the federal standard.

Tower Dumps and Geofence Warrants

Ordinary CSLI requests work forward: investigators have a suspect and want that person’s location history. Tower dumps and geofence warrants work backward. Investigators know when and where a crime happened and want to identify every phone that was nearby.

A tower dump pulls records of all devices that connected to a particular cell tower during a specific time window. These sweeps can return data on thousands of phones, most belonging to people with no connection to any crime. Carpenter explicitly declined to address whether tower dumps trigger Fourth Amendment protection, and lower courts have reached mixed results.³

Geofence warrants are a newer version of the same idea, typically directed at Google or another tech company rather than a carrier. Law enforcement defines a geographic boundary and time frame, and the company identifies every device with location data in that zone. In 2024, the Fifth Circuit held that geofence warrants are “general warrants categorically prohibited by the Fourth Amendment,” calling them “the exact sort of general, exploratory rummaging that the Fourth Amendment was designed to prevent.”⁶

The Supreme Court granted certiorari in Chatrie v. United States in January 2026 to consider the constitutionality of geofence warrants. Oral arguments took place in April 2026. A ruling could either validate the Fifth Circuit’s blanket prohibition or set out a framework under which these warrants can survive constitutional scrutiny with sufficient safeguards.

The Emergency Exception

Federal law allows carriers to bypass the normal warrant process when someone’s life is at stake. Under 18 U.S.C. § 2702, a provider may voluntarily disclose location records or communications to a government entity if the provider believes in good faith that an emergency involving danger of death or serious physical injury requires disclosure without delay.⁷ This covers active kidnappings, missing persons cases, and imminent threats of violence.

One detail catches people off guard: the statute places the good-faith judgment on the carrier, not on law enforcement. The law says the provider “may divulge” if “the provider, in good faith, believes” the emergency exists.⁷ In practice, officers submit a written request explaining the emergency and the carrier’s legal team makes the call, but the statute itself does not require a formal certification from law enforcement as a precondition for disclosure.

The exception is narrow. It covers the immediate emergency, not a general license to browse someone’s location history for an ongoing investigation. If the government later relies on records obtained through an emergency disclosure, defense counsel can challenge whether the emergency was genuine. Evidence gathered through a misrepresented or fabricated emergency is subject to suppression.

What CSLI Can and Cannot Show

CSLI is not GPS. That distinction matters in court and is the most misunderstood aspect of this evidence. A GPS fix can place a phone within a few meters. CSLI tells you which cell tower sector a phone connected to, and that sector typically covers a 120-degree arc radiating outward from the tower. The resulting coverage area can span a few hundred meters in a dense city or several miles in a rural area.

Tower density drives precision. In urban environments, carriers pack towers close together to handle traffic, so each tower’s effective coverage area is smaller. A connection to a downtown tower might place a phone within a few city blocks. In rural areas where towers are miles apart, the same type of record might narrow location only to a wide swath of countryside. Large buildings, weather, and network congestion can cause a phone to connect to a tower that isn’t the closest one, producing data points that mislead if taken at face value.

The bottom line is that CSLI can show someone was in a general area but cannot prove they were at a specific address, inside a particular building, or on a certain street corner. Anyone who tells a jury otherwise is overstating what the data supports.

How 5G Is Changing the Picture

The rollout of 5G is steadily increasing the precision of cell-site data. Traditional 4G macro towers cover large areas, but 5G relies heavily on small cells mounted on streetlights, utility poles, and building facades. These small cells have much shorter range, so each one covers a tighter geographic area, and a connection narrows a phone’s likely location far more than a 4G tower ever could.

Industry projections suggest 5G networks can achieve sub-meter positioning accuracy in some configurations, compared to the roughly 50-to-500 meter range typical of 4G cell-site data. As the data gets more precise, the privacy interests grow stronger, and courts that built their analysis on the assumption that CSLI provides only a rough approximation may need to revisit that reasoning.

How Long Carriers Keep the Records

Retention periods determine whether historical CSLI even exists by the time someone wants it. There is no federal law requiring carriers to retain location data for a specific period, so policies vary. Based on publicly available disclosures in recent years, AT&T retains call detail records that include cell-site information for up to five years, with more granular individual location data kept for roughly 13 months. Verizon retains CSLI for about one year. T-Mobile holds location data for up to 24 months.

These windows matter for prosecution and defense alike. If you need CSLI to build an alibi or challenge the government’s timeline, waiting too long to request preservation can mean the records no longer exist. Defense counsel handling cases where location evidence could be exculpatory should send a preservation letter to the carrier as early as possible. Once the retention window closes, the data is gone, and no court order can bring it back.

Challenging Cell-Site Evidence in Court

CSLI gets attacked on two fronts: whether it was lawfully obtained, and whether it actually proves what the prosecution claims.

Suppression Based on How It Was Obtained

The most direct challenge is a motion to suppress. If law enforcement acquired historical CSLI without a warrant and no recognized exception applies, Carpenter requires exclusion.² Common arguments include that the warrant application lacked probable cause, that the warrant was overbroad in the time period or number of devices covered, or that the emergency exception was invoked without a genuine emergency. Tower dumps and geofence warrants face additional scrutiny as potential general warrants lacking Fourth Amendment particularity.⁶

Challenging the Reliability of the Analysis

Even lawfully obtained CSLI can be attacked through the expert testimony interpreting it, typically under Rule 702 of the Federal Rules of Evidence. Effective challenges focus on several vulnerabilities:

Cell-site analysis techniques used by law enforcement have generally not been validated through independent scientific testing, and no published error rates exist for placing a phone at a location based on tower connections.
An analyst who testifies that a phone was at a particular address based on a tower connection covering a multi-block area is going beyond what the data supports; the evidence shows the phone was somewhere within the tower’s sector, not at a specific point.
Phones do not always connect to the nearest tower. Network load, signal obstructions, and carrier routing can send a connection to a more distant tower, so an analysis assuming closest-tower behavior will produce unreliable conclusions.
Rule 403 arguments can seek exclusion when the risk of jurors treating CSLI as pinpoint evidence substantially outweighs its actual probative value. The expectation that forensic evidence should be definitive is a real concern with this type of data.

Defense teams can also challenge authentication of the carrier’s records, arguing that records maintained for billing purposes are not necessarily reliable for proving a phone’s physical location in a criminal case. The carrier’s systems were built to route calls efficiently, not to produce evidence. That distinction matters when the stakes involve someone’s freedom.

1
Office of the Law Revision Counsel. 18 USC 2703 – Required Disclosure of Customer Communications or Records
2
Cornell Law School Legal Information Institute. Carpenter v United States
3
Supreme Court of the United States. Carpenter v United States
4
Office of the Law Revision Counsel. 18 USC 3122 – Application for an Order for a Pen Register or a Trap and Trace Device
5
U.S. Department of Justice. Use of Cell-Site Simulator Technology
6
Fifth Circuit Court of Appeals. United States v Smith
7
Office of the Law Revision Counsel. 18 USC 2702 – Voluntary Disclosure of Customer Communications or Records