What can you get from a license plate number?
At first glance, a person’s license plate number may not be considered that valuable a piece of information. When tied to a formal Motor Vehicle Administration (MVA) request it can yield the owner’s name, address, type of vehicle, vehicle identification number, and any lienholders associated with the vehicle. While this does reveal some sensitive information, such as a likely home address, there are generally easier ways to go about gathering that information. Furthermore, states have made efforts to protect such data, revealing owner information only to law enforcement officials or certified private investigators. The increasing use of Automated License Plate Readers (ALPRs), however, is proving to reveal a treasure trove of historical location information that is being used by law enforcement and private companies alike. Also, unlike historical MVA data, policies and regulations surrounding ALPRs are in their infancy and provide much lesser safeguards for protecting personal information.
ALPR – what is it?
Consisting of either a stationary or mobile-mounted camera, ALPRs use pattern recognition software to scan up to 1,800 license plates per minute, recording the time, date and location a particular car was encountered. This information is stored in a database and made available for a period of time. ALPR deployment helps law enforcement officers scan plate numbers and run them against a “hot list” of cars that are wanted or stolen. The hit rate is statistically low – one department cited a hit rate of 0.2% – with the majority of data collected by ALPRs dealing with individuals who are not under suspicion of any crime, but whose information is being collected as plates are scanned in the aggregate.
A popular tool in law enforcement, ALPRs have resulted in an ever-growing dataset of historical location information. In one example, during an August 2014 court proceeding, the Los Angeles Police Department revealed that it collects data on nearly 3 million cars per week, equating to nearly half of all vehicles registered in Los Angeles. How this information is accessed and for how long it may be accessed varies on a state-by-state basis. Some states retain the information for a few weeks, while others do so indefinitely.
The legality of these practices and the resulting implications are of obvious concern to proponents of privacy in the digital age. A 2012 email exchange within Federal Bureau of Investigation’s General Counsel halted a purchase order for ALPR equipment as the Bureau considered its effects on individual privacy and sought to establish clear guidelines and procedures for its use.
Details emerge over time
Cyrus Farivar from Ars Technica scratched the surface as to just how much information can be gleaned from ALPR-collected historical location data when he obtained the entire ALPR dataset of the Oakland, California Police Department. The dataset included more than 4.6 million scans of over 1.1 million unique plates between December 2010 and May 2014. After pairing up the data with a simple mapping tool, Farivar was able to quickly assess the general home and work locations of several individuals based on the information.
Not just for law enforcement
ALPR data is of high value to interest groups outside of law enforcement, as well. Lenders, debt collectors, and repo companies have deployed the technology and sought to influence policies around potential restrictions of its use. Many of these companies, whose clients include banks or insurers, already have the information tying the individual to the license plate number, and the use of ALPRs allows them to track down stolen vehicles, or vehicles in default more efficiently.
These same ALPR users claim that they are not invading privacy when gathering license plate information since the plates they scan are available for all to see, and they do not disclose the owner of the plates. Unlike law enforcement agencies, however, these companies have even fewer requirements and existing policies on how long the information is kept and what can be done with it. There is nothing to stop the information from being packaged and sold to anyone, including law enforcement who may use these data brokers as a workaround to their own data-purging requirements.
Outcome is unclear
The legal framework around the treatment of ALPR is still contentious. A 1983 United States Supreme Court decision in United States v. Knotts held that “a person traveling in an automobile on a public thoroughfare has no reasonable expectation of privacy in his movements.” However, Knotts came down before the advent of widespread automated scanning and data collection. This is important because the practice of tracking a car’s movements in the past required one or more individuals to physically follow the vehicle. With today’s technology, on the other hand, this information can be gleaned over time by a patchwork of stationary cameras and city-wide auto-mounted cameras. Moreover, the data can be pieced together retroactively as data points and may be stored indefinitely for later retrieval. As alluded to by Justice Samuel Alito in the 2012 decision in United States v. Jones, regarding warrantless GPS tracking, the Knotts decision may not apply in instances of long-term monitoring and cataloguing of the movement of an individual’s car for a long period of time because it was not within the realm of possibility at that time.
While states grapple to establish laws around the use of ALPRs, its widespread use continues to capture millions of plates and the associated metadata every single day, painting a richer and more detailed picture of the public’s daily travels and routines.
