The United States Supreme Court decided Carpenter vs. United States on June 22, 2018. This is a major Fourth Amendment decision which requires law enforcement to obtain a warrant to get cell phone service provider records that can show a user’s movements.
The broad facts of the case are not complicated. The police arrested four men in connection with a series of armed robberies in April, 2011. One of the men confessed and gave his cell phone number and the numbers of the other actors to law enforcement. This information was used to apply for court orders to obtain “transactional records” for each phone number. The applications were granted under the Stored Communications Act, which provides that the government may require the disclosure of certain telecommunications records when “specific and articulable facts show that there are reasonable grounds to believe that the contents of a wire or electronic communication, or the records or other information sought, are relevant and material to an ongoing criminal investigation.” The transactional records included the dates and times of calls, and the approximate location where calls were made based on the user’s relative location to cell towers. Such material is referred to as “cell site location information” or “CSLI”.
Based on the CSLI, the government charged Carpenter with, among other offenses, Hobbs Act robberies (e.g., robberies that affect interstate commerce). Carpenter moved to suppress the CSLI evidence on Fourth Amendment grounds, asserting that a warrant was required to obtain the records. The district court denied Carpenter’s motion, and the Sixth Circuit affirmed.