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How to deploy automatic license plate recognition ethically and safely

Vehicles driving down a freeway from the perspective of a police car with ALPR technology

Key takeaways and best practices from MCCA guidance

Automatic license plate recognition (ALPR) technology first made land in the US in 1998, but its adoption ramped up significantly in the 25 years that followed. ALPR allows law enforcement agencies to take photos or footage of license plates, pull license plate text from the image and search it against relevant databases. This aids in generating leads and closing cases, but it also raises significant questions about privacy and civil liberties. How can agencies deploy this technology responsibly within the communities they serve?

To answer those questions, the Major Cities Chiefs Association (MCCA) published a comprehensive report of best practices in February 2023. The report gives a detailed overview of the state of ALPR, and was compiled with department administrators, program managers and command staff in mind. Here, we’ll summarize some of the key takeaways and supplement them with information from our own experts to clue you in on how to approach ALPR from buy-in through deployment and beyond.

ALPR challenges

Implementing ALPR has its challenges. Before using this tech in the field, administrators and managers need to consider the privacy concerns raised by ALPR. Only once those issues have been addressed can agency and community leadership be approached for support.

Privacy concerns

The MCCA’s document notes that although some individual states and jurisdictions have passed laws regarding the use of ALPR, no federal legislation has yet been passed specifically targeting ALPR privacy concerns. The MCCA includes many of the state laws in an appendix at the end of its document, but it also, provides a detailed summary of the relevant case law. Precedent dictates that police photographing a plainly visible license plate on a public roadway or from a plainly visible authorized location does not constitute seizure under the Fourth Amendment. Lower courts across the nation have ruled that police can also, without a specific reason, check the status of a plate against a law enforcement database because it does not constitute a search under the Fourth Amendment. A hit on a hot license plate made using ALPR meets the standard for reasonable suspicion to effect a traffic stop.

Where things get messier is in tangential information stored in an ALPR database. That info may includes vehicle location, direction of travel and associated criminal justice information, but the specific data collected varies according to the ALPR system. The more data points tied to personal identity law enforcement uses, the closer it edges toward privacy violations. The Supreme Court has not yet ruled on to what extent ALPR coverage or its corresponding database may infringe upon the Fourth Amendment, but MCCA recommends that agencies take particular care not to provoke unfavorable legislation or judicial decisions that might adversely affect the availability of ALPR tech.

Leadership and community support

Once you’ve determined ALPR to be the right solution, Axon Senior Product Manager Trey Mills recommends you develop policies and a training program even if you haven’t yet made the ALPR tech purchase. Training’s focus should lie more on ensuring policies are understood and adhered to than on the specifics of operating the technology.

Most of the training is in best practices and in driving home enforcement of policies and procedures, regardless of the buttons you have to push to make the technology work,

Mills said in an interview.

Although every community is different, transparency is generally the best policy around ALPR. That means publishing as much information about technology, costs and department policies as you can (without jeopardizing operational security) on public-facing websites, community boards and other forums. Solicit feedback on policies and deployment from the community to ensure they understand how you plan to protect their privacy.

"Across the board, you’re going to do yourself big favors if you are as transparent as you can be, said Mills."

The last thing you want to do is put yourself in a position where you’ve already purchased the tech, and then you run into community resistance or policy requirements enforced by the community that you’re not prepared for, and find out that the equipment you bought that you intended to deploy, you can’t because you didn’t do your homework.

The MCCA recommends bringing in community leaders to see the technology in use according to policy, both at the station house and on ride-alongs. The earlier you begin this phase of the process, the more likely the community will be to support your use of ALPR. That’s why Axon Fleet 3 offers a trial period, giving you, leadership and the community a chance to test the tech before you commit to a purchase. Our rugged, 4K-enabled in-car cameras bring ALPR to its full potential and maintain accountability. Read more about Axon Fleet 3 here.

ALPR best practices

Holistic department policy

Law enforcement agencies aiming to incorporate ALPR must design policies that prevent misuse. Such policies should begin with a statement of purpose and a community-facing statement on why the agency has decided to use ALPR technology. It should go on to describe general use guidelines of the technology and, in detail, describe all the roles and responsibilities of those law enforcement professionals who use it. Only workers trained for ALPR and whose jobs require it should have access to ALPR data, and systems such as user permissions must be put in place to prevent unauthorized access. This helps to prevent the misuse of (or tampering with) data, as do clear outlines for data auditing, retention, and purging.

Written policy should also outline investigative procedures with regard to ALPR, guidance on how to remain transparent on the use and reporting of the technology in court documents, a description of training completed by ALPR-using personnel as well as information about the ALPR vendor including system name and type.

Rigorous training

Written policy and standards are crucial, but training is where the rubber meets the road. “It doesn’t do any good to focus your attention on having a policy if it’s not taught and enforced,” said Mills. With proper training, you can rest assured officers stay within the bounds of legal, constitutional and departmental limitations. MCCA recommends the following components for ALPR training covering:

  • Departmental ALPR policy and safeguards

  • ALPR operation, data sources, vendor and system type

  • The importance of transparency with arresting documentation and auditing responsibilities

  • How ALPR data is kept secure, and for how long

  • Any applicable laws and policies specific to the jurisdiction of deployment

  • Occasional refresher courses with relevant updates to case law

ALPR has proven significantly more effective when cameras are placed according to crime data and patterns. Community leaders or other stakeholders, such as oversight committees, should be consulted before placement in order to prevent First Amendment chilling effects or privacy or defendant rights violations, and permits should be obtained with the appropriate local public works or government entity once those considerations have been satisfied.

MCCA recommends agencies restrict ALPR system and data access to specialized personnel, with a program manager responsible for granting new user access after adequate training. This prevents bad faith ALPR checks and thus maintains respect for privacy, civil rights and civil liberties. ALPR technology should only be used as part of a criminal investigation or to address an articulable public safety concern; unfocused use could lead to significant legal trouble.

Secure data storage, auditing and retention

Just as evidence must display a clear chain of custody, ALPR database records must maintain a clear account of who accesses them and when. Regular auditing of ALPR data usage will help ensure personnel respect written policies.

MCCA recommends agencies collect and report the following ALPR data:

  • Number of detections

  • Number of hotplate hits

  • Number of queries conducted by users

  • Number of arrests directly related to ALPR

  • Number of user-generated hotplates

  • Breakdown of hotplate hit types

  • Year-over-year analysis and trends

ALPR data should be kept no longer than necessary, as determined either by specific legal requirements or agency policy (which should, in turn, be determined with the community and other stakeholders).

I don’t think any agency wants to be on the forefront of litigation because of accusations of abuse or misuse

said Mills.

Data sharing and the future of ALPR

ALPR tech grows more sophisticated each year. “It’s advanced as fast as cell phone camera technology,” said Mills. Soon it will be able to integrate object and vehicle recognition to determine vehicle make and model, color, roof racks, bumper stickers and other identifying features. It’s not technology holding ALPR back — it’s the lack of cooperation among law enforcement agencies.

Sharing ALPR data among agencies benefits all the agencies involved, but the practice has not been standardized nationwide. Anything beyond the sharing of general ALPR detection data should be outlined in a formalized agreement. That way it’s clear to stakeholders what’s being shared, how, which parties are responsible for which parts of the process, and the procedures in place for proper data handling. These relationships should be as transparent as possible without affecting operational integrity.

Transparency should be a core value in ALPR deployment. That’s why Axon worked with an AI & Policing Technology Ethics Board to design Fleet 3’s approach to ALPR ethics and privacy. Fleet 3 implements many of the MCCA’s ALPR best practices, from selectively publishing ALPR policy and usage information to a publicly available web page, to strict, configurable user permissions that prevent unwanted access to data. To learn more about how Axon can benefit your law enforcement practice, get in touch with us today.