Carpenter v. United States
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Summary
Facts
Timothy Carpenter was convicted of a series of armed robberies after the FBI obtained his historical cell-site location information (CSLI) without a warrant using a court order under the Stored Communications Act. CSLI is generated whenever a cell phone connects to a tower, creating a time-stamped record of a person’s movements. The government obtained over 12,000 CSLI data points showing Carpenter’s movements and proximity to the crime scenes. Carpenter challenged the collection of this data without a warrant, arguing that obtaining it without a warrant violated his Fourth Amendment rights.
Legal Question
Did the warrantless acquisition of historical CSLI by the government constitute a search under the Fourth Amendment?
Decision
The Supreme Court held (5–4) that accessing historical CSLI is a Fourth Amendment search and generally requires a warrant supported by probable cause. The Court reasoned that individuals have a reasonable expectation of privacy in their physical movements, even if data is held by third parties like phone companies. The decision declined to extend the traditional third-party doctrine to CSLI, emphasizing that people do not truly share location data voluntarily as it is collected automatically.
The decision marked a significant moment in digital privacy law, limiting government access to sensitive digital data and reaffirming constitutional protections in the age of pervasive technology.