Police freely collect, store, and use ALPR data, with few formal privacy policies and no federal laws for guidance. ALPRs scan every car, regardless of whether the individual driver is suspected of criminal activity. Similar to cell site location information (CSLI) or GPS tracking, historical ALPR records can paint an intimate picture of where a vehicle and its occupants have traveled—including sensitive and private places like our homes, doctors’ offices, and places of worship. Commercial vendors operate vast databases of ALPR records, and sell database access not just to law enforcement agencies, but to private businesses like repossession services and insurance companies. Government employees are frequently able to access records generated by cameras mounted on both private and law enforcement vehicles, giving them access to a vast array of location data. That’s why we think government use of ALPRs could lead to invasive tracking, and necessitates safeguards, such as a warrant requirement.

Vigilant Solutions’ System User Guide and Agency Manager Guide provide invaluable information about how law enforcement uses ALPR technology and the types of data that may be extracted from the system. You can also review the IACP ALPR training slideshow on Cincinnati Police Department’s regional deployment of ALPR technology. Through the California Public Records Act, EFF has obtained training slideshows for the following police departments. 

California passed a law (S.B. 34) that came into effect on January 1, 2016, requiring California counties to develop and publish privacy and usage policies for how their law enforcement agencies deploy ALPR technology. We have posted links to many law enforcement agencies’ ALPR usage and privacy policies. As an example of these policies, you can review the ALPR policy for the Chula Vista Police Department.

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Common ALPR Terminology

Private or Commercial Data – Often public records indicate that an agency has purchased access to “LEARN” or “NVLS,” which is sometimes spelled out as National Vehicle Locator Service or National Vehicle Location System, or some other permutation. These systems allow law enforcement to access data collected by certain other agencies that is hosted by Vigilant Solutions and commercial data collected by Vigilant Solutions’ sister company, Digital Recognition Network.  Vigilant Solutions’ software hosts approximately 10 billion data points, 2/3 of which were collected by private contractors.

“Locate Analysis” – A predictive function offered by Vigilant Solutions’ LEARN System. Police can use this feature to generate a “probabilistic report of when and where to look for a vehicle of interest.” 

“Hot list” – A hot list is a watch list of license plates that can be run against real-time ALPR captures. When a plate is uploaded to a hot list, police can receive real-time alerts on the vehicle’s whereabouts. There are few rules in place for limiting how license plates are added to hot lists.

“Stakeout” – A feature offered by Vigilant Solutions’ LEARN system that allows police to identify license plates that have been captured by ALPR cameras at one or multiple locations.

“Detection Browsing” – In Vigilant Solutions’ LEARN system, this is the function an agency uses to query a license plate, a partial license plate, or the make-model-color of a vehicle. If the police officer uses Vigilant Solutions’ mobile app to query a plate, this function will appear as “License Plate Query Mobile.” This may also be documented as simply “Plate Search.”

“Mobile Hit Hunter” – This is a Vigilant Solutions feature that alerts police within a 3-mile radius in real time when a vehicle on a hot list is seen by a private ALPR vehicle. 

"Possible Associates" - Vigilant Solutions system also allows an officer to search for license plates seen in proximity of another license plate in order to identify potential associates.

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ALPR Search Stats

Law enforcement agencies have data that shows how many license plates were collected and how many matched a "hot list" over a given period of time. EFF has obtained these records from law enforcement via state public records laws; our index of data from these requests are available online through our report: "Data Driven: Explore How Cops Are Collecting and Sharing Our Travel Patterns Using Automated License Plate Readers." If the agency uses Vigilant Solutions' LEARN or PlateSearch system, you can ask for the "Hit Ratio Report," which can be exported easily from the software as a PDF file. 

Our research found that 173 agencies across the United States, collected 2.5 billion license plate scans in 2016-2017, but only .5% of those plates were matched to a hotlist at the time of capture. Obtaining this information may help to show the large scale of and lack of justification for the agency's mass surveillance ALPR program. 

Some states have enacted laws requiring this data to be proactively released. For example, Nebraska state law requires agencies to report annually to the Nebraska Commission on Law Enforcement and Criminal Justice on its ALPR practices and usage. The report, which must be published on the government entities' website, must include: 

  • The names of each list against which plate data was checked;
  • The number of license plates manually searched in the ALPR system;
  • The number of confirmed matches; and
  • The number of matches that were in error.

Maryland state law has even more robust disclosure requirements. By March 1 of each year, agencies that operate ALPR databases in Maryland are required to publicly disclose to the state legislature: 

  • The total number of ALPR units in operation;
  • The total number of ALPR scans;
  • The total number ALPR scans maintained in the database;
  • The total number of requests made for ALPR data, including the number of out-of-state requests, the number of federal requests, and how many of each resulted in the release of information;
  • Any data breaches or unauthorized use of the ALPR database; and
  • A list of audits of the ALPR system.

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The Public's Right to Know

In recent years, EFF, the ACLU, and others have called attention to ALPR’s invasive tracking capabilities and its proliferation across the country. We won a major victory when the California Supreme Court agreed with us that the public has a right to know how police use this technology. Starting with U.S. v. Yang, 2018 WL 576827 (D. Nev. 2018), we will be arguing that government use of ALPRs is a search that implicates the Fourth Amendment, and it should require a warrant in routine investigations.

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