This post was co-authored by EFF legal intern Olivia Miller.

For most Americans—driving is a part of everyday life. Practically speaking, many of us drive to work, school, play, and anywhere in between. Not only do we visit places that give insights into our personal lives, but we sometimes use vehicles as a mode of displaying information about our political beliefs, socioeconomic status, and other intimate details.

All of this personal activity can be tracked and identified through Automatic License Plate Reader (ALPR) data—a popular surveillance tool used by law enforcement agencies across the country. That’s why, in an amicus brief filed with the Virginia Court of Appeals, EFF, the ACLU of Virginia, and NACDL urged the court to require police to seek a warrant before searching ALPR data.

In Commonwealth v. Church, a police officer in Norfolk, Virginia searched license plate data without a warrant—not to prove that defendant Ronnie Church was at the scene of the crime, but merely to try to show he had a “guilty mind.” The lower court, in a one-page ruling relying on Commonwealth v. Bell, held this warrantless search violated the Fourth Amendment and suppressed the ALPR evidence. We argued the appellate court should uphold this decision.

Like the cellphone location data the Supreme Court protected in Carpenter v. United States, ALPR data threatens peoples’ privacy because it is collected indiscriminately over time and can provide police with a detailed picture of a person’s movements. ALPR data includes photos of license plates, vehicle make and model, any distinctive features of the vehicle, and precise time and location information. Once an ALPR logs a car’s data, the information is uploaded to the cloud and made accessible to law enforcement agencies at the local, state, and federal level—creating a near real-time tracking tool that can follow individuals across vast distances.

Think police only use ALPRs to track suspected criminals? Think again. ALPRs are ubiquitous; every car traveling into the camera’s view generates a detailed dataset, regardless of any suspected criminal activity. In fact, a survey of 173 law enforcement agencies employing ALPRs nationwide revealed that 99.5% of scans belonged to people who had no association to crime.

Norfolk County, Virginia, is home to over 170 ALPR cameras operated by Flock, a surveillance company that maintains over 83,000 ALPRs nationwide. The resulting surveillance network is so large that Norfolk county’s police chief suggested “it would be difficult to drive any distance and not be recorded by one.”

Recent and near-horizon advancements in Flock’s products will continue to threaten our privacy and further the surveillance state. For example, Flock’s ALPR data has been used for immigration raids, to track individuals seeking abortion-related care, to conduct fishing expeditions, and to identify relationships between people who may be traveling together but in different cars. With the help of artificial intelligence, ALPR databases could be aggregated with other information from data breaches and data brokers, to create “people lookup tools.” Even public safety advocates and law enforcement, like the International Association of Chiefs of Police, have warned that ALPR tech creates a risk “that individuals will become more cautious in their exercise of their protected rights of expression, protest, association, political participation because they consider themselves under constant surveillance.”  

This is why a warrant requirement for ALPR data is so important. As the Virginia trial court previously found in Bell, prolonged tracking of public movements with surveillance invades peoples’ reasonable expectation of privacy in the entirety of their movements. Recent Fourth Amendment jurisprudence, including Carpenter and Leaders of a Beautiful Struggle from the federal Fourth Circuit Court of Appeals favors a warrant requirement as well. Like the technologies at issue in those cases, ALPRs give police the ability to chronicle movements in a “detailed, encyclopedic” record, akin to “attaching an ankle monitor to every person in the city.”  

The Virginia Court of Appeals has a chance to draw a clear line on warrantless ALPR surveillance, and to tell Norfolk PD what the Fourth Amendment already says: come back with a warrant.

EFF legal intern Noam Shemtov was the principal author of this post.

When police have a warrant to search a phone, should they be able to see everything on the phone—from family photos to communications with your doctor to everywhere you’ve been since you first started using the phone—in other words, data that is in no way connected to the crime they’re investigating? The Michigan Supreme Court just ruled no. 

In People v. Carson, the court held that to satisfy the Fourth Amendment, warrants authorizing searches of cell phones and other digital devices must contain express limitations on the data police can review, restricting searches to data that they can establish is clearly connected to the crime.

The realities of modern cell phones call for a strict application of rules governing the scope of warrants.

EFF, along with ACLU National and the ACLU of Michigan, filed an amicus brief in Carson, expressly calling on the court to limit the scope of cell phone search warrants. We explained that the realities of modern cell phones call for a strict application of rules governing the scope of warrants. Without clear limits, warrants would  become de facto licenses to look at everything on the device, a great universe of information that amounts to “the sum of an individual’s private life.” 

The Carson case shows just how broad many cell phone search warrants can be. Defendant Michael Carson was suspected of stealing money from a neighbor’s safe. The warrant to search his phone allowed the police to access:

Any and all data including, text messages, text/picture messages, pictures and videos, address book, any data on the SIM card if applicable, and all records or documents which were created, modified, or stored in electronic or magnetic form and, any data, image, or information.

There were no temporal or subject matter limitations. Consequently, investigators obtained over 1,000 pages of information from Mr. Carson’s phone, the vast majority of which did not have anything to do with the crime under investigation.

The Michigan Supreme Court held that this extremely broad search warrant was “constitutionally intolerable” and violated the particularity requirement of the Fourth Amendment. 

The Fourth Amendment requires that warrants “particularly describ[e] the place to be searched, and the persons or things to be seized.” This is intended to limit authorization to search to the specific areas and things for which there is probable cause to search and to prevent police from conducting “wide-ranging exploratory searches.” 

Cell phones hold vast and varied information, including our most intimate data.

Across two opinions, a four-Justice majority joined a growing national consensus of courts recognizing that, given the immense and ever-growing storage capacity of cell phones, warrants must spell out up-front limitations on the information the government may review, including the dates and data categories that constrain investigators’ authority to search. And magistrates reviewing warrants must ensure the information provided by police in the warrant affidavit properly supports a tailored search.

This ruling is good news for digital privacy. Cell phones hold vast and varied information, including our most intimate data—“privacies of life” like our personal messages, location histories, and medical and financial information. The U.S. Supreme Court has recognized as much, saying that application of Fourth Amendment principles to searches of cell phones must respond to cell phones’ unique characteristics, including the weighty privacy interests in our digital data. 

We applaud the Michigan Supreme Court’s recognition that unfettered cell phone searches pose serious risks to privacy. We hope that courts around the country will follow its lead in concluding that the particularity rule applies with special force to such searches and requires clear limitations on the data the government may access.