Carpenter v. United States

Between 2010 and 2011, a crew robs a series of RadioShack and T-Mobile stores across Michigan and Ohio at gunpoint. After arrests, an accomplice gives the FBI phone numbers. Instead of seeking a warrant, agents use a court order under the Stored Communications Act, which requires only "reasonable grounds," to pull months of cell-site location records for Timothy Carpenter's phone: 12,898 location points tracking his movements over 127 days. The records place his phone near four robberies. He is convicted and sentenced to more than 100 years. His appeal asks a question the Constitution's authors could not have imagined: is your phone's location history yours?

The government argues settled doctrine: records you voluntarily share with a third party, like the numbers you dial or the bank deposits you make, carry no expectation of privacy, and location pings are just business records the carrier happens to keep. Carpenter argues that a phone is not optional in modern life and logs its owner's location around the clock without any voluntary act, so months of retrospective tracking gives the government a perfect surveillance record of a person's whole life, the kind of monitoring the Fourth Amendment exists to prevent.

If the government wins, the third-party doctrine swallows the digital age: everything your devices report to any company is available to law enforcement without a warrant. If Carpenter wins, the Fourth Amendment starts adapting to technology, and courts must draw new lines around data that did not exist when the doctrine was built. Either way, the robberies were real and the convictions stood. The question is what everyone else's phone records cost.