The 5-4 ruling creates a higher legal burden for police than that which previously existed under federal law. Digital privacy advocates hailed it as a major victory.
The June 22 decision relates to the case of Timothy Carpenter. Police convicted Carpenter in several armed robberies in Ohio and Michigan with the help of past cellphone location data that linked him to crime scenes.
Writing for the majority, conservative Chief Justice John Roberts said that obtaining the sort of data from wireless carriers used in the Carpenter conviction — but without a warrant — amounted to an unreasonable search and seizure under the U.S. Constitution’s Fourth Amendment. The court’s four liberal justices joined Roberts in the majority; the court’s four other conservatives dissented.
The ruling, however, does not resolve other important digital privacy questions — such as whether police also must obtain warrants to access real-time cellphone data to track suspects.