WASHINGTON -- The Supreme Court says police generally need a search warrant if they want to track criminal suspects' movements by collecting information about where they've used their cellphones.

  • 5-4 decision announced Friday
  • Outcome marks change in how police can obtain phone records

The justices' 5-4 decision Friday is a victory for privacy in the digital age. Police collection of cellphone tower information has become an important tool in criminal investigations.

The outcome marks a big change in how police can obtain phone records. Authorities can go to the phone company and obtain information about the numbers dialed from a home telephone without presenting a warrant.

Chief Justice John Roberts wrote the majority opinion, joined by the court's four liberals.

Roberts said the court's decision is limited to cellphone tracking information and does not affect other business records, including those held by banks.

He also wrote that police still can respond to an emergency and obtain records without a warrant.

Justices Anthony Kennedy, Samuel Alito, Clarence Thomas and Neil Gorsuch dissented. Kennedy wrote that the court's "new and uncharted course will inhibit law enforcement" and "keep defendants and judges guessing for years to come."