Cell-Site Simulators (Stingrays): Do Police Need a Warrant?

In the federal courts of the Fourth Circuit, yes: a published majority opinion from September 24, 2026 says the Fourth Amendment requires a valid warrant before police use a cell-site simulator, often called a Stingray, to find a phone. Justice Department agents are also supposed to get a warrant under a 2015 department policy, and Maryland requires one by statute. Elsewhere the answer depends on state law, and the U.S. Supreme Court has not ruled on simulators specifically.

What is a cell-site simulator and how do police use it?

A cell-site simulator is a device that imitates a real cell tower so that phones nearby connect to it. The Fourth Circuit's opinion describes how this works: simulators "prompt all nearby cellphones to automatically send an electronic signal to the simulator, thereby revealing the location of each cellphone and, in most instances, the location of the cellphone's owner."

Officers can carry a handheld unit and walk an area while watching the strength and direction of the signal until they home in on one phone. The court noted that this location data is available instantly and is generally more precise than the location records a phone company keeps. Because the police get the signal themselves, they can find the phone without asking the carrier for its location.

The opinion also describes a side effect. When the Hailstorm model used in this case connects to a phone, the owner cannot receive calls (other than a 911 call) or text messages. It connects to, and temporarily makes unusable, every phone in the area that uses the same cellular carrier.

Do police need a warrant to use a Stingray?

It depends on where you are and which police are involved. In the Fourth Circuit (federal courts in Maryland, Virginia, West Virginia, North Carolina, and South Carolina), the majority opinion in Andrews v. Baltimore City Police Department says a warrant is required. A 2015 Justice Department policy tells that department's agents to get a warrant first. Maryland has a statute requiring one, Md. Code Ann., Crim. Proc. § 1-203.1.

Outside those places there is no single national answer. State courts and courts in other circuits are not bound by the Fourth Circuit, although they may find its reasoning persuasive. The Supreme Court's cellphone location decisions, Carpenter v. United States (2018) and Chatrie v. United States (2026), apply everywhere, but neither involved a cell-site simulator. Your state may have its own statute or court decision, and that is worth checking.

Exigent circumstances, such as an emergency where officers cannot wait, are a general exception to the Fourth Amendment's warrant requirement. The Andrews opinion did not address how that exception would apply to simulators, so no one should assume it either always applies or never applies.

Who is Kerron Andrews and what happened to him?

In 2014, Baltimore detectives were investigating a shooting that injured three people. They suspected Kerron Andrews, who had previously worked with police as an informant, and they got an arrest warrant charging him with attempted murder. They did not know where he lived, so a detective asked a Baltimore court for a pen register order, a type of court order that does not require the showing a warrant does.

The order brought records from Andrews's phone company. Those records narrowed his phone's location to the 5000 blocks of Clifton Avenue, which hold about thirty-five townhomes. Detectives then walked up and down those blocks with a Hailstorm simulator until it connected to his phone and pinpointed a specific townhome. A woman who answered the door consented to the officers coming in. They found Andrews on the living room couch with his phone in his pocket.

Prosecutors charged him. Police had signed a nondisclosure agreement with the FBI as a condition of getting the Hailstorm, and the use of the simulator was not revealed to Andrews's lawyer until a year into the criminal case. Once it came out, a Maryland trial court suppressed the evidence and Maryland's intermediate appellate court agreed that using the simulator without a warrant violated the Fourth Amendment. The charges were dismissed. By then Andrews had spent nearly two years in pretrial detention.

What did the Fourth Circuit decide about warrants?

Andrews then sued for damages. In the opinion, Judge Berner, joined by Judge Heytens, wrote: "We hold that the use of the cell-site simulator constituted a search within the meaning of the Fourth Amendment." Elsewhere the majority put it this way: "the Fourth Amendment requires a valid warrant for the use of a cell-site simulator."

The majority gave several reasons. It relied on Carpenter and Chatrie, which held that police conduct a search when they acquire stored records of a phone's movements from a phone company (Carpenter) or a tech company (Chatrie). It pointed to Chatrie's statement that where the Fourth Amendment applies, it applies regardless of the quality or quantity of information the government obtains, so it did not matter that a simulator gives a snapshot of one moment instead of a long history. It noted that the simulator was more precise than the carrier data, and that it was used to find a person inside a home. Citing Kyllo and Karo, earlier Supreme Court cases about technology that reveals what is inside a home, the court said the simulator "crack[ed] open the front door" of the townhome.

The court also stressed a difference from Carpenter and Chatrie. In those cases police got data that people share with companies. Here police collected the location information directly, by briefly taking control of the phone. The court observed that "no federal court of appeals has squarely addressed" this question, and then answered it for its own circuit.

Why did Andrews lose his lawsuit anyway?

A ruling that the simulator use was a search did not get Andrews any money. The court affirmed judgment for the defendants on three separate grounds.

The first is qualified immunity. This doctrine protects individual officers from paying damages unless they violated a right that was "clearly established" when they acted. In plain terms, a court asks whether earlier decisions made the law clear enough that every reasonable officer would have understood the conduct was unlawful. The Fourth Circuit concluded that in 2014 it was not. The Supreme Court had never addressed simulators, and the court found a lack of clear guidance from other circuits as well. Andrews's own criminal case was the first time a Maryland appellate court had considered whether using one is a search.

The second is a Maryland state-law immunity for public officials, which applies unless an official acted with malice or gross negligence. The court found that the unclear law, together with the detectives' reliance on the pen register order, ruled that out.

The third concerns the city. A police department can be held liable only when its own policy or custom caused the violation. Andrews pointed to the FBI nondisclosure agreement, but after three years of discovery he had no other evidence, and the court said he had not shown the agreement was carried out unconstitutionally. The court added a warning that police "may not rely on a private nondisclosure agreement as an excuse to conceal or obfuscate important information when seeking a search warrant or information it is required to disclose in court proceedings."

This outcome matters going forward. A published ruling now exists in the Fourth Circuit, which may make it harder for officers there to argue that the law was unclear, although officers may point to the concurrence and argue that part of the opinion is not binding. That is not a guarantee that a future plaintiff will win, since the other defenses and the facts of each case still count. For more on how this doctrine works, see the qualified immunity test.

Did all three judges agree that a warrant is required?

No, and the difference affects how much weight the ruling carries. Judge Quattlebaum agreed that the detectives had qualified immunity and joined the rest of the judgment, but he disagreed with the majority's decision to address whether there was a search at all.

The defendants had conceded in the district court that using the simulator was a search, and neither side appealed that point. He wrote that the privacy question was "far from clear," because there are significant differences between this case and Carpenter and Chatrie. He also questioned "the precedential value" of analyzing only part of the first step of the qualified immunity test when the outcome rested entirely on the second step. He also believed the pen register order, which asked for permission to use a cellular tracking device, satisfied the warrant requirement.

The majority disagreed and said lower courts have discretion over the order in which they take up the two questions. It also said it did not need to decide whether the pen register order met the warrant requirement. So the opinion states a warrant requirement in two votes out of three, and a defendant or officer in a later case may argue that this part is not binding. How a later court treats it is not something this article can predict.

The opinion also notes a contrast from the Seventh Circuit. Before Chatrie, in United States v. Hammond (2021), that court held that police use of live location information obtained from a phone company was not a search. It stressed that the case did not involve tracking inside a home. The Fourth Circuit pointed out that in Andrews's case, tracking inside a home is exactly what happened.

What do the Justice Department policy and Maryland law require?

The opinion says that in 2015, after a congressional investigation, the Justice Department adopted a policy requiring federal law enforcement officials to seek a warrant before using this technology in a criminal investigation. The department's September 3, 2015 press release says agents "must now obtain a search warrant supported by probable cause before using a cell-site simulator."

The same release lists exceptions. It describes "limited exceptions in the policy for exigent circumstances or exceptional circumstances where the law does not require a search warrant and circumstances make obtaining a search warrant impracticable," and says components must track and report the number of times the technology is used under those exceptions. It also says the policy bars using simulators to collect the contents of any communication in criminal investigations, which it says includes data on the phone itself, such as emails, texts, contact lists, and images. When the equipment is used to locate a known device, the release says all data must be deleted as soon as the device is located, and no less than once daily.

Two limits are important. This is a department policy, not a statute, and it covers Justice Department components. It does not bind a city police department like the one in Baltimore.

On the state side, the opinion says Maryland's legislature passed a law in 2014, several months after Andrews's arrest, requiring a warrant before a cell-site simulator is used. The opinion also cites a 2024 Fourth Circuit case, United States v. Briscoe, which found that a court order issued under one subsection of that statute counts as a valid search warrant for this purpose. This article does not describe other states' laws, because they were not part of this ruling.

What can you do if you think police tracked your phone?

You usually cannot tell whether a simulator is being used on your phone. Apps that claim to detect them can be unreliable, so be cautious about trusting one.

1. If you are charged with a crime, tell your defense lawyer exactly how officers found you. Ask whether the police reports mention how your phone or location was identified.
2. Ask your lawyer to request discovery about how police located you, including any warrant, court order, or application that mentions a tracking device. In Andrews's case, the use of the simulator surfaced only a year into the case.
3. If the records show a simulator or other real-time tracking was used, talk with your lawyer about a motion to suppress. Our explainer on motions to suppress covers how that works. Whether the evidence is excluded can depend on details such as whether a court order existed and what exceptions apply.
4. If you were never charged but believe you were tracked unlawfully, a civil suit for damages exists, but the Andrews case shows the hurdle: immunity doctrines, plus the need to prove a city policy or custom to hold the city itself liable. Legal aid groups and court self-help centers can tell you what deadlines apply in your state.
5. To learn more about the general rules, read about real-time phone tracking and how to tell if police are tracking your phone. For a related question, see police use of location data you did not know was on.

Could this ruling still change?

Yes. The opinion was issued on September 24, 2026. Further review, such as a request for rehearing or a petition to the Supreme Court, is possible, and this article does not predict whether either will happen or how it would turn out. Check the current status before relying on the ruling. You can read the full opinion on the court's published PDF.

The decision also leaves several questions open, including whether the pen register order used against Andrews satisfied the warrant requirement, and how the emergency exception applies. Courts outside the Fourth Circuit are free to reach their own conclusions.

This is general legal information, not legal advice for your situation. If police may have used a tracking device on you, talk to a criminal defense lawyer or a legal aid office.

The law behind your rights

The Fourth Amendment protects the data on your phone and the digital location records it generates, so police generally need a warrant to search your device or track you through it, and that protection applies to state and local police through the Fourteenth Amendment.

Constitutional basis: Fourth Amendment, Fourteenth Amendment. Your state constitution may add further protections.

Key court cases:

• Riley v. California, 573 U.S. 373 (2014) — police must get a warrant before searching the digital contents of a cell phone seized from an arrestee.
• Carpenter v. United States, 585 U.S. 296 (2018) — accessing historical cell-site location records that track a phone's movements is a Fourth Amendment search requiring a warrant.

These are landmark federal cases that establish the rights described above. How they apply can depend on your state, the federal circuit you are in, and the specific facts of an encounter. This is general legal information, not legal advice.