ACLU warns of mass tracking through license plate scanners

Updated 4:59 p.m. Eastern Time

The American Civil Liberties Union is warning that law enforcement officials are using license plate scanners to amass massive and unregulated databases that can be used to track law-abiding citizens as their go about their daily lives.

In a new report, "You Are Being Tracked: How License Plate Readers Are Being Used to Record Americans' Movements," the ACLU discusses the data culled from license plate scanners - cameras mounted on patrol cars, overpasses and elsewhere to record your license plate number and location at a given time. There are tens of thousands such cameras now in operation, according to the group, with the data in some cases being stored indefinitely. 

The cameras, which are often installed thanks to federal funding, are designed to catch car thieves and other criminals. The ACLU's Catherine Crump writes that the organization does not object to "when they're used to identify people who are driving stolen cars or are subject to an arrest warrant." But, she continues, "they should not become tools for tracking where each of us has driven." 

Law enforcement says the scanners are valuable tools. The Los Angeles Police Protective League said the technology has helped in thousands of cases, including to locate a suspect in a violent rape and sodomy case. In a blog post, the group called for responsible policies to monitor use but maintained that "law enforcement agencies must have the freedom to use tools that can aid their efforts to keep their communities safe." 

The ACLU report is the result of an analysis of 26,000 pages of documents from police departments around the country, obtained through nearly 600 freedom of information requests. It finds that while some jurisdictions keep the information gleaned from the scanners for a short time - 48 hours in the case of the Minnesota State Patrol - many hold onto the data for years. That includes the Delaware Department of Homeland Security and the state of New Jersey, which keep the data for five years, and towns in Texas and New York, which are presumed to keep the data indefinitely. 

The organization complains that there are "virtually no rules in place" to keep officials from tracking "everybody all the time." The town of Grapevine, Texas reported scanning an average of 14,547 plates each day in September 2012 and said it had nearly 2 million plates stored in its database. Milipitas, California has 4.7 million plates in its database. Neither town has a policy in place to regulate that data. The ACLU also warns that the data is being fed into larger databases, with the private National Vehicle Location Service now holding more than 800 million license plate records. The group's database is used by more than 2,200 law enforcement customers.

"Trips to places of worship, political protests, or gun ranges can be powerful indicators of people's beliefs," writes Crump. "Is it really the government's business how often you go to the drug store or liquor store, what doctors you visit, and the identities of your friends?" The report warns that the data can be used in an official capacity to spy on protesters or target communities based on their religious beliefs, or unofficially by a police officer who wants to keep an eye on a romantic rival.

The ACLU is calling for regulations to be put in place to prevent broad-based tracking using the scanners. It said the scanners should be used in a limited capacity, that the data be stored for less than a month unless it has been specifically flagged, that the public should be able to find out if a plate is contained in a database, that the data not be shared with third parties, and that scanner usage be reported publicly on an annual basis.