Carpenter v. United States, 585 U.S. ___, 138 S.Ct. 2206 (2018), is a landmark United States Supreme Court case concerning the privacy of historical cell site location information (CSLI). The Court held that the government violates the Fourth Amendment to the United States Constitution when it accesses historical CSLI records containing the physical locations of cellphones without a search warrant.
Prior to Carpenter, government entities could obtain cellphone location records by claiming the information was required as part of an investigation. After Carpenter, government entities are required to obtain a search warrant to access that information. Recognizing the influence of new consumer communications devices in the 2010s, the Court expanded its conceptions of constitutional rights toward the privacy of this type of data. However, the Court emphasized that the Carpenter ruling was narrowly restricted to the precise types of information and search procedures that were relevant to Carpenter's complaint.
Background
Cell site location information (CSLI) Cellular telephone service providers are able to find the location of cell phones through either global positioning system (GPS) data or cell site location information (CSLI), in the process of connecting calls and data transmissions. CSLI is captured by nearby cell towers, and this information is used to triangulate the location of phones. Service providers capture and store this data for business purposes, such as troubleshooting, maximizing network efficiencies, and determining whether to charge customers roaming fees for particular calls.
The data can also illustrate the historical movements of a cellphone. Thus, anyone with access to this data has the ability to know where the phone has been and what other cell phones were in the same area at a given time. When users travel with their cellphones, this data can theoretically illustrate every place a person has traveled, and possibly other people encountered via their corresponding data.
The third-party doctrine
Prior to Carpenter, the Supreme Court consistently held that a person had no reasonable expectation of privacy in regard to information voluntarily turned over to third parties such as telephone companies, and therefore a search warrant is not required when government officials seek this information. This legal theory is known as the third-party doctrine, established by the Supreme Court in Smith v. Maryland (1979), in which the Court determined that government can obtain a list of phone numbers dialed from a suspect's phone.
By the 2010s, cellphones and particularly smartphones had become important tools for nearly every person in the United States. Many applications, such as GPS navigation and location tools, require a cellphone to send and receive information constantly, including the exact location of the phone. As technology advanced in the 2010s, the Supreme Court began to modify its precedents on government searches of personal communications devices, given new consumer behaviors that may transcend the third-party doctrine.
Facts of the case
Between December 2010 and March 2011, several individuals in the Detroit, Michigan area conspired and participated in armed robberies at RadioShack and T-Mobile stores across the region. In April 2011, four of the robbers were captured and arrested. The petitioner, Timothy Carpenter, was not among the initial group of arrestees. One of those arrested confessed and turned over his phone so that FBI agents could review the calls made from his phone around the time of the robberies. The agents obtained a search warrant to inspect the information in the phone, in order to find additional contacts of the arrestee and compile more evidence about the crime ring.
From the historical cell-site records, the agents confirmed that Timothy Carpenter was also part of the crime ring, and proceeded to compile information about the location of his phone over 127 days. In turn, this information revealed that Carpenter had been within a two-mile radius of four robberies at the times they were perpetrated. This evidence was used to support Carpenter's arrest. At criminal court, Carpenter was found guilty of several counts of aiding and abetting robberies that affected interstate commerce and another count of using a firearm during a violent crime. He was sentenced to 116 years in prison.