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Automatic License Plate Recognition

November 25, 2014


There has been no shortage of debate, frustration, and outright paranoia over government use of surveillance equipment in recent times, and Americans’ reasons for suspicion seem to be constantly growing in number. A tool in the U.S. government’s arsenal that recently has become more commonly used is the automatic license plate reader (ALPR). This device, usually mounted in pairs on the back of police cruisers or on traffic lights at major intersections, is capable of capturing images of license plates automatically. The images captured can then be immediately saved and cross-referenced with a variety of databases that might contain the average citizen’s information. Even from a basic description, one can see how technology like this might be prone to abuse. In examining the variety of potential and confirmed uses of this technology, it is clear that public concern is warranted.

ALPRs have been around for some time, however recently their deployment has become far more widespread. According to a report done by the Police Executive Research Forum (PERF) about 71% of all police departments in the United States utilize ALPRs as of 2012. As mentioned they tend to be found on the back of police cruisers and at major intersections, however they are not limited to those locations. The devices can be mounted anywhere on any road and are constantly photographing license plates. The cameras themselves are highly advanced; recent models are able to capture license plates of any style under any lighting condition and they can capture a lot of them. In 2012, the town of Grapevine, Texas reported that its police department on average captured the images of 14, 547 unique plates a day and had over 2 million plates stored in their database. Some individual ALPRs mounted on highway overpasses are capable of capturing the license plates of every vehicle that passes underneath them.

Since these ALPRs are deployed widely and take thousands of images every day, it is very difficult for any car to avoid detection. On the positive side of things this technology can help police officers track down missing persons, suspected or known felons and terrorists, sex offenders, or those in violation of their parole. The negative side is that the ALPRs send images of all the license plates they capture to police databases where they are saved regardless of whether or not the plate belongs to a person the police are looking for. Given the widespread deployment of these cameras it is likely that images of most people’s (at least those in urban areas) license plates are stored in a police database. Saved with the license plate number are the location, date, and time of image taken, which allows for officers to track the movement of any car. In some towns and cities officers can also input known license plates into their cruiser’s computer and receive alerts when the plate gets captured by a camera. This plethora of information that is available to the officers certainly makes it hard for wanted or suspected criminals in previously identified vehicles to escape detection, however it could have a variety of other less ideal uses.

Given the fact that the ALPRs store the information of every plate they capture, a list of troubling possibilities has been developing as the use of this technology has become more universal. Since these databases hold so many license plate numbers for indefinite amounts of time, were that data be leaked accidentally the effect could be enormous. As for police use of the data, officers could establish patterns of travel and driving habits for any given person. From there they could obviously deduce things like where one goes to church, where they get medical care, or whom they associate with. In other words, all of the things we tend to keep to ourselves and those we are acquainted with. When it comes to the alert feature, any officer could potentially use the alerts to track down anyone they want provided they know the person’s plate number. An officer could also use the alert system to deal with personal affairs that have no bearing on police matters whatsoever.

These concerns are not just speculation, some of them have already occurred in practice. Recently the Boston Police Department suspended its ALPR program after the license plate numbers of 68,000 individuals were accidentally leaked to the Boston Globe. Fortunately there were no negative consequences since the Globe was the only institution that received the leak, however the occurrence of such incident suggests that the information might not be perfectly secure and that future leaks could occur. In New York it was reported that some officers used ALPRs in unmarked vehicles and drove around local mosques in order to catalog the license plates of those in attendance. This shows clearly that not only are these devices a threat to privacy, but that they also serve as a potential tool to enable improper police work. Given these incidents and those that could potentially occur it is clear that police use of ALPRs needs to be reevaluated and put under stricter scrutiny.

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