Read the full story on the UC Berkeley Law School website.

On a late summer night, in July 2012, California resident Paul Macabeo rolled his bicycle through a stop sign. The street was deserted, but, unbeknown to Macabeo, a patrol car with its lights off had been trailing him. As soon as he rode through the sign, the cops pulled him over.

The officers found his cell phone and searched it—without a warrant and without his consent. Scrolling through the phone, they found illegal photos of child pornography. The officers had only intended to cite Macabeo for failure to stop, a minor infraction. But once they discovered the photos, they handcuffed him and locked him up. He was found guilty of a felony and sentenced to five years of probation.

At the time, Macabeo couldn’t have known that his bike ride—and the cell phone search—would lead to a legal battle that could impact millions of Californians.

Although seemingly one man’s battle against the government, People v. Macabeo “raises a significant issue” with far-reaching implications, said Catherine Crump, a privacy law expert at UC Berkeley’s law school.

Simply put, the issue concerns the legality of a warrantless search: when it can take place and why. Police are only allowed to conduct a search without a warrant during—or after—an arrest. But in Macabeo’s case, the facts show that police had no intention of arresting him. They searched his cell phone anyway—and then decided to arrest him after they found the photos.

Putting aside the nature of the photos — the search was illegal, said law professor Charles Weisselberg. Giving the police “sweeping authority” to search anyone suspected of even minor traffic infractions, regardless of whether they are being arrested, “raises the troubling prospect of widespread searches of people going about their daily lives,” he said.

“It means that any officer in California who sees a speeder, or a person who’s parked illegally, or someone who’s riding a bicycle the wrong way on the street, or a pedestrian who steps into the crosswalk when the red light is starting to flash—they could be stopped and their person and their belongings could be searched,” he added.