Carpenter v. United States
What's at Stake
The Supreme Court ruled that the government needs a warrant to access a person’s cellphone location history. The court found in a 5 to 4 decision that obtaining such information is a search under the Fourth Amendment and that a warrant from a judge based on probable cause is required.
In 2011, without getting a probable cause warrant, the government obtained several months’ worth of cell phone location records for suspects in a criminal investigation in Detroit. For one suspect, Timothy Carpenter, the records revealed 12,898 separate points of location data—an average of 101 each day over the course of four months. The Supreme Court heard the case on November 29, 2017.
After Carpenter was convicted at trial, based in part on the cell phone location evidence, he appealed to the Sixth Circuit Court of Appeals. The ACLU, along with the ACLU of Michigan, Brennan Center, Center for Democracy & Technology, Electronic Frontier Foundation, and National Association of Criminal Defense Lawyers, filed an amicus brief arguing that the government violated the Fourth Amendment when it obtained the location records from Carpenter’s wireless carrier without a warrant.
After a divided panel of the Sixth Circuit held that no warrant is required under the Fourth Amendment, the ACLU became co-counsel with Carpenter’s defense attorney to file a petition for review by the Supreme Court. In June 2017, the Supreme Court agreed to hear the case.
Sixth Circuit Opinion
Gov't Response to Supplemental Authority Letter
Supplemental Authority Letter re Graham
Sanders's Reply Brief
Carpenter's Reply Brief
Supreme Court Decision
Reply Brief for Petitioner
Amicus Briefs In Support of Respondent United States
Brief for the United States
- Center for Competitive Politics, Center for Media Justice, Color of Change, Americans for Prosperity Foundation, and Tea Party Patriots
- Center for Democracy and Technology
- Competitive Enterprise Institute, Cato Institute, Reason Foundation, and Committee for Justice
- Data & Society Research Institute and Fifteen Scholars of Technology and Society
- Empirical Fourth Amendment Scholars
- Electronic Frontier Foundation, Brennan Center for Justice, The Constitution Project, National Association of Criminal Defense Lawyers, and National Association of Federal Defenders
- Electronic Privacy Information Center (EPIC) and Thirty-Six Technical Experts and Legal Scholars
- Institute for Justice, Carole Hinders, Randy and Karen Sowers, and DKT Liberty Project
- The Reporters Committee for Freedom of the Press and 19 Media Organizations
- Restore the Fourth, Inc.
- Rutherford Institute
- Scholars of Criminal Procedure and Privacy
- Scholars of the History and Original Meaning of the Fourth Amendment
- Technology Companies (In Support of Neither Party)
- Technology Experts (represented by the Knight First Amendment Institute at Columbia University)
- United States Justice Foundation, Gun Owners Foundation, Gun Owners of America, Inc., et al.
Brief for Petitioner
Reply to Brief in Opposition
Brief for the United States in Opposition
Cato Institute Amicus Brief
Electronic Frontier Foundation, et al, Amicus Brief
Supreme Court Cert Petition