After years of contradictory appeals court decisions, the US Supreme Court will finally hear a case about how private your cell phone location should be.

At the heart of the case is a simple question: should the cops be required to get a warrant to obtain your location record from your mobile phone company?

That question has resulted in a number of different decisions and convictions. In 2015, the Fourth Circuit Court of Appeals in Virginia decided that the whereabouts of you and your phone are protected under the Fourth Amendment – meaning protected from unreasonable searches by the cops and Feds.

That decision reflected a similar ruling by the Fifth Circuit in 2013. And similar arguments are being heard in the Ninth Circuit as we speak. However, the Eleventh Circuit came to the opposite conclusion in 2015. And the Sixth Circuit also decided in 2016 that the fourth amendment did not apply.

This has resulted in a patchwork of contradictory laws across the country – making it a seemingly obvious case for the Supreme Court to take on.

It is the last case – over armed robber Timothy Carpenter – that will now progress to the court where the issue should be decided once and for all. (The court previously refused to hear an appeal over the Eleventh Circuit's decision.)

Evidence

Timothy Carpenter was arrested in 2011 as part of an investigation into armed robberies at Radio Shack and T‑Mobile USA stores in and around Detroit. The police went to mobile phone operators and retrieved four months' worth of location data that showed Carpenter was near each of the locations when they were robbed (or, more accurately, his phone was).

Carpenter's phone was recorded in over 200 separate cell tower sectors, so a detailed view of his movements was possible. More importantly for prosecutors, they showed a pattern of behavior, such as where he made calls in the evening – presumed to be where he was living. On the night of one of the robberies, his calls came from a different location.

Carpenter's lawyers tried to fight the introduction of that evidence, arguing that it broke his Fourth Amendment rights – which protect US citizens from unreasonable searches and seizures. But that effort failed, the cell phone location evidence was introduced, and Carpenter was convicted on six counts of robbery.

His lawyers appealed – focusing in on this issue of unreasonable searches – but lost the appeal with the Sixth Circuit arguing that no warrant was required to access Carpenter's location data.

Every year, the four main cell phone companies in the US – AT&T, Sprint, T‑Mobile and Verizon – receive tens of thousands of requests from law enforcement for location data (known as CSLI or cell site location information).

The dispute is over what legal standard needs to apply for that data to be handed over: is it "probable cause" – which requires the police to prove to a judge that they have more than just a hunch that the person in question was involved and get a warrant for the data? Or is it "reasonable suspicion" – which basically means the cops can grab the data of anyone they think might be involved.

Opposite views

As you might expect, civil liberties groups are appalled at the idea that a cop's hunch gives them the right to access highly personal data. And, as you also might expect, law enforcement wants to retain the ability to grab that data quickly and easily without having to build evidence and go through a judge.

The civil liberties' argument is that the approach breaks the Fourth Amendment; law enforcement's is that under the Stored Communications Act it only needs to show there are "reasonable grounds" to get hold of the "relevant and material" information for its case.

The counter-argument to that is that the act – which was passed in 1986 – did not imagine that modern smartphones would contain as much or as highly personal data as they do.

And in many respects that is the key issue at the heart of this case – a lack of legislation to deal with the modern, digital world (thanks in large part to a deadlocked partisan Congress). Without updated laws, law enforcement is falling back on interpretations of older laws to do what it thinks is necessary, and that is in turn leading to countless legal challenges from groups claiming that those interpretations are faulty and we should rely instead on the constitution.

The American Civil Liberties Union (ACLU) had been one of the main groups pushing back, and it will lead the Supreme Court argument on behalf of Carpenter.

"Because cell phone location records can reveal countless private details of our lives, police should only be able to access them by getting a warrant based on probable cause," said ACLU attorney Nathan Freed Wessler. "The time has come for the Supreme Court to make clear that the longstanding protections of the Fourth Amendment apply with undiminished force to these kinds of sensitive digital records."

Previous

If recent history is anything to go by, the Supreme Court is likely to find in favor of Carpenter and agree that the Fourth Amendment should stand, absent more specific legislation. There have been a number of major cases on the intersection between law enforcement and modern digital technology and the court has fallen down on the side of the individual each time.

Most significant was in 2014, when the Supreme Court decided that the cops need a warrant to search a seized cell phone. Their logic? The laws being relied on were written before smartphones existed.

Chief Justice John Roberts wrote the decision in that case and argued that the huge amount of data stored on phones means police cannot routinely inspect phones as they would the contents of arrested people's pockets and wallets.

"Modern cell phones are not just another technological convenience. With all they contain and all they may reveal, they hold for many Americans 'the privacies of life'," he said.

That same logic is likely to apply in this new case about location data, setting up another landmark decision over digital data and privacy. ®