Supreme Court will decide the fate of your digital privacy

The big picture: The Supreme Court has ruled in the past that you don't have a "reasonable expectation of privacy" for data you voluntarily turn over to a third party.

• In the '70s, it said police could use a pen register — a device that records all numbers called from a particular telephone line — to log the numbers a suspect dialed from his landline phone, because he knew he was routing those calls through the phone company. A similar case allowed warrantless searches of bank records.
• But here in 2017, almost everything we do involves transmitting data to a third party. As the ACLU put it in a brief to the high court, every day, millions of Americans disclose "their search queries to Google, their GPS coordinates and location history to Apple, Google, and Waze, their intimate photos to Apple or Flickr, and their medical queries to WebMD."

The details: The ACLU is representing Timothy Carpenter, who was convicted of participating in a string of robberies in 2010 and 2011 — a conviction based partly on data from Carpenter's cell phone providers, which showed that his phone pinged cell towers near the sites of the robberies at the times they occurred.

• Police obtained nearly 13,000 individual records about the location of his cell phone, spanning four months.
• The ACLU says obtaining all those cell-tower records without a warrant violated Carpenter's Fourth Amendment rights against unreasonable search and seizure.

The Justice Department's case is simple: Cell-tower records are just like the bank records and pen registers of the '70s.

• Users don't own their cell-tower records; cell-phone companies do.
• And everyone who uses a cell phone knows about cell towers.
• So, cell-tower location records are a clean example of data turned over to a third party, and therefore aren't entitled to any expectation of privacy.

But the tech industry disagrees. More than a dozen big tech companies — including Apple, Microsoft, Facebook, Google, Twitter and Snap, as well as Verizon — filed a brief that doesn't take a side in the dispute over these particular phone records, but argues that the court's "analog" precedents shouldn't govern modern technology.

The implications the companies lay out are staggering:

• "Users may not expect or intend that, by relying on service providers to administer everything from their email content and address book to their health and fitness data, they assume the risk that the government could amass and monitor their data without a warrant," the companies wrote.
• "When an Internet user opens a news story, views a photograph, or sends a message to a friend, the user's smartphone often makes a record of that action, and those records are often transmitted to third parties," they say. Similarly, "smart" appliances know when we're home.
• All told, there's almost nothing these companies, together, don't know about us.

Several of the justices, both liberal and conservative, seem to share those concerns. The court ruled in 2014 that police need a warrant to physically search a suspect's cell phone, largely because of the sheer amount of information our phones store. And in 2011, the court said police needed a warrant to attach a GPS tracker to a suspect's car.

That's different from retracing their steps through cell-tower locations, but the justices were clearly thinking about some of the same issues they'll grapple with today.

• Justice Sonia Sotomayor said the court should reevaluate its so-called third-party doctrine, because it's "ill suited to the digital age, in which people reveal a great deal of information about themselves to third parties in the course of carrying out mundane tasks."
• Long-term GPS tracking required a warrant because "society's expectation has been that law enforcement agents and others would not and … simply could not secretly monitor and catalogue every single movement of an individual's car for a very long period," Justice Samuel Alito said in the same case.

A ruling is expected by June.