License plates are more than numbers and letters you display on your car. When police photograph your license plate, scan it, record the precise times and locations of the scans, and store all that information indefinitely in a database, they can search this information to piece together your movements and travel patterns. It’s highly personal information that reveals where we go, who we visit, and other details of our private lives.

Yesterday we filed an amicus brief asking the Virginia Supreme Court to hold that the state’s law enforcement agencies must purge plate information they collect using Automated License Plate Readers (ALPRs) because it’s personal information. A state law called the Government Data Collection & Dissemination Practices Act, enacted in response to concerns over the increasing use of technologies by governments and companies to compile detailed information about citizens’ private lives, requires agencies to delete personal information. We want the court to protect our privacy and establish that the bar is high for the police to retain personal information.

Mounted on squad cars and at fixed, roadside locations such as street lights, ALPRs are sophisticated camera systems that read license plates and record the time, date, and location a particular car was encountered. ALPRs typically have a continuous connection to a computer server and, in many cases, are never turned off. They can scan up to 1,600 plates per minute, capturing the plate numbers of millions of innocent, law-abiding drivers who aren’t under any kind of investigation and just living their daily lives.

The data can be mingled with other law enforcement database and enable police to learn where we are and when, whether it’s at our house of worship, our doctor’s office, a political meeting, or a gun show. Harrison Neal, a resident of Fairfax County in Virginia, is concerned by these ongoing privacy violations. The Fairfax County Police Department uses ALPRs that read every license plate that goes by, and stores the records for up to a year. Mr. Neal’s plate was collected at least twice. He sued with the help of the ACLU of Virginia, arguing that the Data Act requires the police to purge their ALPR data. (In California, a 2015 law supported by EFF also added data collected by ALPR as “personal information.”)

A judge in Fairfax County threw the case out, ruling that ALPR data isn’t “personal information” under the state’s Data Act, in one of the first such rulings of its kind in the nation. A license plate number can lead police to a vehicle, not a person, the judge reasoned. The decision flouts a finding by the Virginia Attorney General’s office, which determined ALPR data that wasn’t immediately linked to a criminal investigation was “personal information” protected by the law.

The judge’s interpretation belies the reality of modern life and widespread government surveillance, in which our private, personal information is constantly being collected, stored and aggregated—and is a magnet for law enforcement. Police claim ALPR data can help them locate suspects and solve crimes. But the overwhelming majority of the billions of plates and vehicle locations collected by ALPRs belong to innocent people who have committed no crime. A 2009 joint project between the Fairfax Police Department and the Virginia State Police found a high error rate in license plate readers—a scan of 69,000 vehicles produced 12 bogus hits and recovered four stolen vehicles, a success rate of far less than one percent. Yet police query ALPR data for months or even years after it was collected.

Citizens need strong policies and statutes that push back against law enforcement’s attitude that ALPR data isn’t private because licenses are in plain sight, and that collected data should be kept for months or years on the off chance that it might someday be used to investigate a crime. We hope the Virginia Supreme Court leads the way, and recognizes that ALPR data reveals highly detailed pictures of our daily lives and associations and that data collected on non-criminals is personal information and should be promptly purged.

EFF thanks the Brennan Center for Justice for joining our amicus brief, and Matthew Erausquin of Consumer Litigation Associates, P.C., for serving as our local counsel.