Law-enforcement technologyAutomatic license plate readers used to collect, store data on millions of Americans

License plate readers mounted to the trunk of a police car // Source: khmer71.net

Automatic license plate readers are the most widespread location tracking technology available to law enforcement. Mounted on patrol cars or stationary objects like bridges, they snap photos of every passing car, recording their plate numbers, times, and locations. At first the captured plate data was used just to check against lists of cars law enforcement hoped to locate for various reasons (to act on arrest warrants, find stolen cars, etc.). An ACLU blog post notes that increasingly, however, all of this data is being fed into massive databases that contain the location information of many millions of innocent Americans stretching back for months or even years.

The civil rights organization says that this is what it has found after analyzing more than 26,000 pages of documents from police departments in cities and towns across the country, obtained through freedom of information requests by ACLU affiliates in thirty-eight states and Washington, D.C.“As it becomes increasingly clear that ours is an era of mass surveillance facilitated by ever cheaper and more powerful computing technology (think about the NSA’s call logging program), it is critical we learn how this technology is being used,” the ACLU says, adding that license plate readers are just one example of a growing trend: the government is increasingly using new technology to collect information about American citizens, all the time, and to storing it forever — providing a complete record of citizens’ lives for the government to access at will.

Yesterday, the ACLU released all of the documents it has received (accessible through this interactive map and this issue page), and published a report, You Are Being Tracked, which explains what these documents say about license plate readers: what they are capable of, how they are being used, and what privacy harms they can cause if protections are not put in place. The ACLU is also offering more than a dozen recommendations it thinks local police departments and state legislatures should follow when they pass laws about this technology.

See this demonstration of the technology:

The ACLU notes that as is often the case with surveillance technology, there are unobjectionable — even beneficial — uses of license plate readers, and that the organization does not object when these technologies are used to identify people who are driving stolen cars or are subject to an arrest warrant. The ACLU stresses, however, that these technologies should not become tools for tracking where each American has driven.

The organization says that there is a reasonable way to regulate this technology. The primary law enforcement use of these systems is to take pictures of plates to make it possible to check them against “hot lists” of cars of interest to law enforcement. This can be done virtually instantaneously. While plates that generate a “hit” may need to be stored for investigative purposes, there is no need to store plates for months or years to achieve this purpose.

The answer to regulating license plate readers is thus to have strict limits on how long plate data can be retained. “While we don’t recommend a specific cutoff date, we think it should be measured in days and weeks, not months and certainly not years,” the ACLU says.

— Read more in You Are Being Tracked: How License Plate Readers Are Being Used to Record Americans’ Movements (ACLU, 17 July 2013)