Only a couple of weeks before Christmas in 2010, a series of robberies hit Detroit, other parts of Michigan, and neighboring Ohio. They lasted for over a year. In total, six different Radio Shack electronics and T-Mobile stores were robbed at gunpoint. The suspects filled plaid laundry bags with smartphones, and made off with them.

According to the FBI, Timothy Ivory Carpenter and Timothy Sanders, two 29-year-olds from Detroit, orchestrated the robberies. Carpenter planned them, brought the guns, and waited for his accomplices in a stolen car across the street. Both men were eventually convicted. Carpenter was sentenced to 116 years in prison. He later appealed the case, arguing that cellphone location data included as evidence should be thrown out, because it was obtained without a warrant.

Carpenter’s lawyers say that prosecutors obtained 127 days’ worth of cellphone location records from Metro PCS, which placed his phone at over 12,000 different locations. The records contained an enormous amount of personal information. Law enforcement could tell on which Sundays he attended church, and even when Carpenter didn’t spend a night at his own home. Last year, the Sixth US Circuit Court of Appeals upheld the lower court’s ruling. Now, Carpenter’s case is going to the Supreme Court.

On Wednesday, the Supreme Court will hear arguments about whether law enforcement violated the Fourth Amendment in prosecuting the case, which protects against unreasonable search and seizure. Carpenter v. United States could potentially transform electronic privacy protections in the US, either greatly weakening them, or ensuring they are more robust than ever.

The Fourth Amendment was written in the 1700s, and doesn’t yet account for a world in which we carry around devices that constantly monitor our movements and contain all of our communications. Carpenter v. United States will decide whether the government has the right to compel mobile providers and technology companies to hand over that information without a warrant. The court’s decision may affect more than just cell phone location data, as it could also impact whether the government can obtain emails and text messages.

“Because we always have our cell phones with us, their location history reveals a lot about our personal lives. This is exactly the kind of private information the Fourth Amendment was designed to protect,” American Civil Liberties Union attorney Nathan Freed Wessler, who will represent Carpenter before the court, said in a press release. “The government’s argument, based on rulings from the analog era, would free it to get comprehensive records of what websites we view, what Google searches we enter, and even our voice commands to smart devices—without constitutional limit.”

Orin Kerr, a prominent Fourth Amendment scholar at George Washington University, filed a brief in support of the government. He argues that cellphone location data just simulates what happens in the real world. You can’t expect to have privacy when you go outside and walk to the store, so you also aren’t entitled to privacy when it comes to the cellphone location records that show you went there, he argues. A neighbor could have seen you leave your house, in the same way that your cellphone provider has record of it.

The government also argues that you voluntarily consent to sharing your information with third-party providers like mobile carriers and tech companies when you use your phone. If you don’t want the government having access to your information it argues, then don’t use a cellphone, or turn it off frequently.

Tech companies like Apple, Facebook, and Google disagree with the government’s argument. They filed an amicus brief with the Supreme Court, urging it to bring Fourth Amendment protections into the digital age. “All digital technology transmits user information to various service providers. Those transmissions are an unavoidable condition of using digital technology,” the brief reads. “But in this digital era, users may not expect or intend that, by relying on service providers...they assume the risk that the government could amass and monitor their data without a warrant.”

The Stored Communications Act, a federal law, already requires prosecutors to demonstrate “specific and articulable facts showing there are reasonable grounds to believe” that electronically stored data they are seeking is relevant to an ongoing criminal investigation. But the law, passed in 1986, doesn’t require that prosecutors show probable cause, which is required to obtain a warrant.

In some previous cases involving phone records, the court has ruled that no warrant is required. In Smith v. Maryland for example, a case from 1979, the court ruled that there’s no reasonable expectation to privacy when making calls from a landline. One of the lawyers who argued in favor of the court’s ruling in that case, Stephen H. Sachs, said the court should rule differently in Carpenter V. United States in an op-ed for the Washington Post.

“When the Supreme Court decided Smith, in the pre-dawn of the digital age, we didn’t know about the Internet, smartphones, cloud computing, Facebook or Twitter. No one involved in the case could foresee the digital revolution that was to come,” Sachs wrote.

In more recent cases however, the court has favored a person’s right to privacy. In Riley v. California, from 2014, the court ruled that police should generally have a warrant in order to search the cellphone of a person under arrest.

Even if the Supreme Court does rule in favor of Timothy Carpenter, he likely won’t be released from prison, because of another part of the Fourth Amendment. The Good Faith Exception says that if law enforcement obtained evidence believing they were acting according to legal authority, it’s still admissible, even if the laws change.

In other words, because the FBI thought it was acting legally when it obtained Carpenter’s cellphone location data, it will likely still be valid evidence in court. Carpenter’s life likely won’t be altered by his case, but it will impact the level of digital privacy the rest of us can expect from the US government.

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