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Carpenter v. United States

Supreme Court of the United States

November 29, 2017, Argued; June 22, 2018, Decided

No. 16-402.


 [**515]  Chief Justice Roberts delivered the opinion of the Court.

This case presents the question whether the Government conducts a search under the Fourth Amendment when it accesses historical cell phone records that provide a comprehensive chronicle of the user’s past movements.

There are 396 million cell phone service accounts in the United States—for a Nation of 326 million people. Cell phones perform their wide and growing variety of functions by connecting to a set of radio antennas called “cell sites.” Although cell sites are usually mounted on a tower, they can also be found on light posts, flagpoles, church steeples, or the sides of buildings. Cell sites typically have several directional antennas that divide [***8]  the covered area into sectors.

Cell phones continuously scan their environment looking for the best signal, which generally comes from the closest cell site. Most modern devices, such as smartphones, tap into the wireless network several times a minute whenever their signal is on, even if the owner is not using one of the phone’s features. Each time the phone connects to a cell site, it generates a time-stamped record known as cell-site location information (CSLI). The precision of this information depends on the size of the geographic area covered by the cell site. The greater the concentration of cell sites, the smaller the coverage area. As data usage from cell phones has increased,  [*2212]  wireless carriers have installed more cell sites to handle the traffic. That has led to increasingly compact coverage areas, especially in urban areas.

Wireless carriers collect and store CSLI for their own business purposes, including finding weak spots in their network and applying “roaming” charges when another carrier routes data through their cell sites. In addition, wireless carriers often sell aggregated location records to data brokers, without individual identifying information of the sort at [***9]  issue here. While carriers have long retained CSLI for the start and end of incoming calls, in recent years phone companies have also collected location information from the transmission of text messages and routine data connections. Accordingly, modern cell phones generate increasingly vast amounts of increasingly precise CSLI.

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138 S. Ct. 2206 *; 201 L. Ed. 2d 507 **; 2018 U.S. LEXIS 3844 ***; 86 U.S.L.W. 4491; 27 Fla. L. Weekly Fed. S 415; 2018 Comm. Reg. (P & F) 64; 2018 WL 3073916


Notice: The LEXIS pagination of this document is subject to change pending release of the final published version.

Subsequent History: As revised June 29, 2018.


United States v. Carpenter, 819 F.3d 880, 2016 U.S. App. LEXIS 6670 (6th Cir.), 2016 FED App. 89P (6th Cir.) (6th Cir. Mich., Apr. 13, 2016)

Disposition: Reversed and remanded.


privacy, cell-site, subpoena, phone, compulsory, seizures, customers, carriers, tecum, site, duces, third-party, technology, surveillance, telephone, wireless, robberies, Founders, disclosure, common-law, tracking, intrusion, digital, belong, sector, Telecommunications, bailment, ongoing, user, monitoring

Constitutional Law, Fundamental Rights, Search & Seizure, Scope of Protection, Probable Cause, Criminal Law & Procedure, Expectation of Privacy, Warrants, Business & Corporate Compliance, Communications Law, Overview & Legal Concepts, Privacy, Communications Law, Regulated Entities, Telephone Services, Cellular Services, Federal Acts, Stored Communications Act, Preliminary Proceedings, Discovery & Inspection, Discovery by Government, Exigent Circumstances, Warrantless Searches