Carpenter v. United States

A Supreme Court case challenging warrantless access to cellphone location data

On August 15, 2017, the Knight Institute filed an amicus brief in Carpenter v. United States, the case in which the Supreme Court considered whether the government must obtain a warrant before acquiring data that cellphone providers collect about their users’ movements. 

Cellphone providers routinely record detailed information about their users’ locations — technology that rivals the precision of GPS systems. Law enforcement agencies are increasingly requesting cellphone location information from cellular service providers, with AT&T receiving close to 60,000 requests in 2015 alone. Officials had been obtaining this data without securing warrants, and without broad public awareness that cellphone providers even possessed it.

The Knight Institute represented leading technology experts who filed an amicus brief with the Supreme Court, arguing that the Fourth Amendment prohibits the government from obtaining cellphone location data without a warrant.

Status: Decided on June 22, 2018. In a 5–4 decision, the Supreme Court held that the government must get a warrant in order to obtain seven or more days of cell-site location information.

Case Information: Carpenter v. United States, No. 16-402 (Supreme Court).


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