Supreme Court rules that police generally need a warrant to access cell phone data

The Supreme Court ruled that police generally need a search warrant to review cell phone records that include data like a user's location, which will impose a higher bar for law enforcement to access data collected on the millions of people who use smartphones on a daily basis.

The plaintiff in the case, Timothy Carpenter, was convicted of multiple robbery and gun offenses in 2010 but challenged the conviction saying that officers investigating the case didn't get a warrant for his cell phone records. The government argued that law enforcement doesn't need a warrant to get cell phone records from the service provider since it's a third party.

The Court ruled that the government's search, in this case, did not meet the bar for probable cause for a warrant because investigators only had to show that argue the cell phone data might be related to an ongoing investigation in order to get access to it from the cell phone provider.

Chief Justice John Roberts wrote in the majority decision that the government is obligated to get a warrant before compelling a wireless provider to provide cell phone records in an investigation.

"We decline to grant the state unrestricted access to a wireless carrier's database of physical location information," Roberts said. "In light of the deeply revealing nature of (cell site location information), its depth, breadth, and comprehensive reach, and the inescapable and automatic nature of its collection, the fact that such information is gathered by a third party does not make it any less deserving of Fourth Amendment protection."

ABC News Supreme Court contributor and Cardozo law professor Kate Shaw said that the ruling is in line with some of the Court's other efforts to update the Fourth Amendment protection from unreasonable search and seizure to keep up with new technology.

"Here, the Court explains that shifts in technology require revisiting what’s known as the "third party doctrine," the idea that if you’ve knowingly shared information with a third party, you have a reduced expectation of privacy in that information," Shaw said. "The government argued that by "sharing" information about his location with his cell phone company, the defendant had lost any expectation of privacy, but the Court rejects that argument, finding that the defendant had a reasonable expectation of privacy and that a warrant was required to access information about his location derived from cell towers."

The Court also specified that the ruling does not apply to searches from cell phone data not directly related to this case, including national security or foreign affairs cases, real-time information, or information on all devices connected to a specific cell phone town during a particular time frame.

Justices Anthony Kennedy, Clarence Thomas, Samuel Alito, and Neil Gorsuch all dissented to the decision to strike down the lower court's ruling in favor of the government.

Kennedy said in a dissent, also signed by Thomas and Alito, that the Court's decision was a "stark departure" from previous Fourth Amendment cases where the Court has ruled that individuals don't have protection from unreasonable search and seizure when it relates to business records owned and controlled by a third party. He called the majority decision "incorrect" and said it "unhinges" the previous doctrine in Fourth Amendment cases and "draws an unprincipled and unworkable line" between cell phone location data and other records used in investigations such as financial or other phone records.

"The new rule the Court seems to formulate puts needed, reasonable, accepted, lawful, and congressionally authorized criminal investigations at serious risk in serious cases, often when law enforcement seeks to prevent the threat of violent crimes," Kennedy said. "And it places undue restrictions on the lawful and necessary enforcement powers exercised not only by the Federal Government, but also by law enforcement in every State and locality throughout the Nation."

The American Civil Liberties Union, which argued for Carpenter in the case, called the decision a "groundbreaking victory for Americans' privacy rights" and will help protect other kinds of digital information.