Supreme Court Carpenter v. U.S.: Warrant Required to Access Cell Site Location Information

In a recent 5-4 decision, the Supreme Court held that police generally need a search warrant to gain access to your cellphone’s location information. Specifically, in Carpenter v. United States, the Court noted allowing the police to access minute-to-minute location information is the type of surveillance the Constitution’s framers sought to protect against without a search warrant. The Court went on to say that giving police this tracking information without a warrant would be akin to making someone wear an ankle-monitor without a judge’s order.

The Fourth Amendment & Cell Site Location Information

The Fourth Amendment protects your property interests and provides for some privacy protections. The text of this amendment states that you are protected from unreasonable searches and seizures, and that you, your home, your papers, and your things are secure and protected from warrantless search. Furthermore, warrants are to be issued only when probable cause is found, supported either by oath or other affirmation, which includes detail on what is to be searched, where it will be searched, and the person or items that need to be seized.

Probable cause is present for a crime when your actions (facts and circumstances) lead to a reasonable suspicion and need for further information. As the Court reiterated, warrants need “some quantum of individualized suspicion.” U.S. v. Martinez-Fuerte, 428 U.S. 543, 560–561 (1976).

The point of the Fourth Amendment is to keep the government from unreasonably intruding into your life and your freedom. This being said, there are exceptions (consent to the search, imminent danger, exigent circumstances, a search incident to arrest, items in plain view, etc. to name a few) to Fourth Amendment protections, so long as the government is doing the searching and so long as the search is reasonable.

Cell Phone Location Data

Cell phones communicate with cell sites, which can be found at cellphone towers, some light-posts, tops of buildings, and many other areas. When you move with your cell phone, the phone connects to these cell sites and when you place a call or send a text, the phone time stamps the activity which can be stored. This time-stamped information is called cell-site location information or CSLI. Cell site location information is often stored by service providers for years.

There are over 300,000 cell sites in the United States. Your cellphone provider takes the information relayed to cell sites and stores the information to improve their service and coverage. Today, CSLI includes location information that is fairly accurate.


cell site data

Carpenter v. United States (2018)

After a string of robberies in 2010 and 2011, police caught several suspects. Ironically, the robberies were for cell phones being taken from stores like Radio Shack and T-Mobile.  One of them confessed to a series of nine robberies and provided details about their leader, Timothy Carpenter. The police then requested an order for 127 days of tracking information from Carpenter’s cellphone provider. Using all the data received, there were 12,898 data points regarding locations that followed Carpenter’s movements. The location on Carpenter’s phone closely matched the places where robberies occurred and this location information was used as evidence in his conviction. Carpenter was convicted of multiple robbery counts and multiple counts of carrying a firearm during a federal, violent crime.

Carpenter appealed arguing that he was protected from a warrantless search of his cell phone records. Instead of getting a warrant, the police had obtained a court order using the Stored Communications Act (18 U. S. C. §2703(d)). This law allows phone companies to give your records to police if there were reasonable grounds to believe that the records needed would move a criminal investigation along. The standard was lower using this law than the requirements for a warrant, since police just needed specific and articulable facts that led to a reasonable belief that information requested would be related and important (relevant and material) to the investigation. The Stored Communications Act requires “specific and articulable facts showing there are reasonable grounds to believe” that electronic data being sought is relevant to an ongoing criminal investigation. The Stored Communications Act, however, did not require a showing of probable cause.

Carpenter argued obtaining his Cell Site Location Information amounted to a Fourth Amendment search. The Supreme Court focused on whether the third-party doctrine applied to cell site location information. The third-party doctrine provides that the Fourth Amendment is not implicated when the police obtain information revealed to third parties (like bank records and call records.)

Expect to see litigation involving cell site simulators to reach the Supreme Court.

What Changed with Carpenter v. United States?

Before, police did not need a warrant for a lot of cellphone information because if you were sharing your information with a third party, like your cellphone provider, getting access, for example, to the numbers you called was not protected. However, the justices recognized in this decision how tied we are to our phones, and that being able to track a phone’s location when it is practically always in our pockets, would be a gross violation of our expectation of privacy without first obtaining a search warrant.

The Court found that the facts of this case put it between two areas of law: your expectation of privacy when it comes to your location and your movements versus your expectation of privacy when you voluntarily give your information over to third parties (i.e. your cellphone provider). This ruling distinguished previous case law, such as giving over records of numbers dialed or business records from location-related records. In previous cases, information sought was more limited. Here, location information is a “comprehensive record” that provides accurate details of where you have been. Additionally, the court analyzed the fact that cell phones can log your location without you actually using the phone other than turning it on. Because of these two important facts, the Court held that unless an exception to the warrant requirement applies, police generally need a warrant supported by probable cause to be able to access location records.

What Does Carpenter v. United States Cover?

Specifically, the decision covered location information (CSLI). Police need a search warrant to access this location information from your phone.

What Does Carpenter v. United States Exclude?

Case precedent involving financial, banking, and office-related records still holds. Furthermore, warrantless searches may be performed in cases of emergencies or in cases of threats to national security. The Court specifically stated that the decision was very narrow, and that the decision did not cover real time CSLI or “tower dumps,” which is the process of downloading information about all the devices connected to a specific cell site during a specific time frame.

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Was your cell site location information obtained without a warrant in a criminal case? Give us a call at 817-203-2220 or contact us online.


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About the Author Board Certified Lawyer Benson Varghese

About the Author

Benson Varghese is the managing partner of Varghese Summersett. He is a seasoned attorney, highly esteemed for his comprehensive knowledge and expertise in the field. He has successfully handled thousands of state and federal cases, ranging from misdemeanor driving while intoxicated cases to capital offenses, showcasing his commitment to preserving justice and upholding the rights of his clients. His firm covers criminal defense, personal injury, and family law matters. Benson is also a legal tech entrepreneur. Benson is a go-to authority in the legal community, known for his ability to explain complex legal concepts with clarity and precision. His writings offer a wealth of in-depth legal insights, reflecting his extensive experience and his passion for the law. Not only is Benson an accomplished litigator, but he is also a dedicated advocate for his clients, consistently striving to achieve the best possible outcomes for them. His authorship provides readers with valuable legal advice and an understanding of the complexities of the criminal justice system. CriminalPersonal InjuryFamily Law Contact
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