Flock Safety and Automated License Plate Readers: Balancing Public Safety, Privacy, and the Fourth Amendment: Part Five – Best Practices for the Constitutional Use of ALPR and Flock Technology
The previous four articles in this series examined automated license plate reader (ALPR) and Flock Safety technology from a constitutional perspective. Article I introduced the technology and discussed its capabilities, benefits, and the concerns it has generated. Article II examined the Supreme Court decisions that form the constitutional framework governing modern surveillance technology. Article III analyzed how lower courts have applied those principles to ALPR and Flock systems when determining whether accessing historical ALPR data constitutes a Fourth Amendment search. Finally, Article IV addressed one of the most common operational questions facing patrol officers—whether an ALPR or Flock alert provides reasonable suspicion to justify stopping a vehicle.
This final article moves from constitutional analysis to practical application. It discusses best practices for officers and investigators using ALPR and Flock technology in the field and then translates those practices into the framework of a model departmental policy. The recommendations that follow are drawn from the constitutional principles discussed throughout this series, the emerging case law, established CJIS security principles, and recognized law enforcement best practices. They are intended to help agencies maximize the investigative value of ALPR technology while minimizing constitutional risk and protecting the privacy and civil liberties of the communities they serve.
I. Best Practices for Officers and Investigators
The cases discussed throughout this article offer several practical lessons for officers using ALPR or Flock technology in the field. Although every investigation is different, following these principles will place officers in the strongest constitutional position should their actions later be challenged in court.
First, verify the license plate. While this may seem obvious, officers should ensure that the license plate displayed on the vehicle matches the information contained in the alert. Optical character recognition (OCR) technology is remarkably accurate, but no automated system is immune from occasional errors. If possible, check the tag number on your state’s database or NCIC to verify that system matches the information provided on the ALPR alert.
Second, read the entire alert rather than simply reacting to the audible notification. Many ALPR systems provide considerably more information than simply indicating that a “hit” has occurred. The alert may identify the underlying reason for the notification, identify the originating agency, indicate whether the alert is based upon an active warrant or a stolen vehicle report, provide vehicle descriptors, or include officer safety information. The legal significance of the alert often depends upon these additional details.
Third, determine why the vehicle generated the alert. An active arrest warrant, a stolen vehicle report, or a suspended driver’s license, as previously discussed, generally presents much different legal authority than an informational “locate vehicle” entry. Officers should understand the nature of the alert before initiating a stop.
Fourth, consider whether anything you observe negates reasonable suspicion. Does the driver plainly differ from the registered owner when the inference that the owner is driving forms the basis for the stop? Does the vehicle match the make, model, color, and other descriptors contained in the alert? Has anything occurred that calls the accuracy of the database information into question? These observations should be considered when deciding if there is reasonable suspicion to stop the vehicle.
Fifth, remember that informational alerts are not the same as criminal alerts. Agencies frequently enter vehicles into ALPR systems simply to locate them during an investigation. Unless the underlying circumstances themselves establish reasonable suspicion or probable cause, the mere existence of a “locate” alert does not necessarily authorize a traffic stop. Officers should determine the purpose of the entry whenever practical before taking enforcement action.
Finally, document exactly what the ALPR system displayed before initiating the stop. Officers should record the nature of the alert, the originating agency, the reason for the alert, the time of the notification, and any corroborating observations made before activating emergency equipment. These details often become critical during suppression hearings months or even years after the event. A well-documented report demonstrates that the officer relied upon objective facts—not simply an unexplained electronic notification.
Ultimately, ALPR technology should be viewed as an investigative aid rather than a substitute for sound police work. The cases consistently reward officers who use the technology as one component of a thoughtful constitutional analysis rather than as an automatic basis for enforcement action. This approach not only produces stronger constitutional cases, but it also reinforces public confidence that technology is being used responsibly, lawfully, and in a manner that respects both public safety and individual liberty.
II. Best Practices for Police Executives
The cases discussed throughout this series demonstrate that the constitutionality of ALPR and Flock technology depends on far more than the actions of the individual officer making a traffic stop. Increasingly, courts examine the reliability of the underlying system, the manner in which information is collected and retained, the safeguards implemented by the agency, and whether the technology is used in a manner consistent with constitutional principles. Consequently, agency leadership plays a critical role in ensuring that ALPR technology remains both an effective investigative tool and a constitutionally sound law enforcement practice.
A thoughtfully designed ALPR program should begin with a comprehensive written policy. The policy should clearly define the purpose of the technology, identify authorized uses, prohibit unauthorized uses, establish supervisory responsibilities, and provide guidance for officers who rely upon ALPR information during criminal investigations and traffic stops. Written policies not only promote consistency among agency personnel, but also demonstrate that the agency has taken reasonable steps to ensure that the technology is used lawfully and responsibly.
Equally important is the designation of a program administrator. Every agency should identify a supervisor responsible for the day-to-day administration of the ALPR program. Among other responsibilities, the program administrator should oversee user permissions, maintain audit logs, coordinate with prosecutors regarding evidentiary issues, review requests for data sharing, and ensure compliance with applicable state law, CJIS Security Policy requirements, and agency policy. Concentrating these responsibilities in a single position promotes accountability while ensuring consistent program management.
Training is another essential component of a successful ALPR program. Initial instruction should extend well beyond the mechanics of operating the software. Officers should understand the constitutional principles governing ALPR technology, the distinction between historical database searches and vehicle stops, the significance of different types of alerts, and the importance of verifying information before taking enforcement action. Refresher training should be conducted annually and whenever significant changes occur in the law or in the technology itself. Supervisors should receive additional instruction addressing policy compliance, auditing responsibilities, and legal developments affecting the agency’s use of the system.
Access to ALPR data should likewise be carefully controlled. Agencies should limit access to personnel who have successfully completed department-approved training and who require the information to perform official law enforcement duties. Each user should receive unique login credentials protected by multi-factor authentication, and every search conducted within the system should be recorded in a permanent audit log. Agencies should require users to sign an acceptable-use agreement acknowledging that ALPR information may be accessed only for legitimate law enforcement purposes and that unauthorized use may result in discipline, termination, criminal prosecution, or civil liability.
Routine auditing is equally important. Audit logs should be reviewed periodically to ensure that personnel are accessing the system for legitimate investigative purposes. Audits should identify the case number or justification supporting each search, detect unusual search patterns, and identify potential misuse of the system. Many agencies conduct quarterly reviews of user activity in addition to a comprehensive annual audit by command staff. These reviews not only deter misuse but also demonstrate organizational accountability should the agency’s ALPR program later be challenged.
Executive leadership should also establish clear standards governing data retention and information sharing. Data should be retained only as long as permitted by applicable law and agency policy, with records associated with criminal investigations preserved in accordance with established evidence retention schedules. Likewise, information sharing should be limited to legitimate law enforcement and prosecutorial purposes, with documented approval procedures and appropriate records of all disclosures. Agencies should remember that simply because information can be shared does not necessarily mean it should be shared. Data will also be retained in accordance with the applicable state’s record retention schedule.
As artificial intelligence becomes increasingly integrated into ALPR technology, agencies should adopt policies recognizing that AI is intended to assist decision-making rather than replace it. AI-generated recommendations, vehicle recognition, predictive analytics, or investigative suggestions should never substitute for independent police judgment. Officers remain responsible for evaluating the accuracy of the information, determining whether reasonable suspicion or probable cause exists, and ensuring that all enforcement actions comply with constitutional requirements.
Perhaps most importantly, agencies should recognize that, as legal compliance is a top priority, public confidence is also of high importance. Citizens generally support the use of technology to reduce crime, recover stolen vehicles, locate missing persons, and apprehend violent offenders. That support can quickly erode, however, if the public believes the technology is being used for indiscriminate surveillance or to monitor individuals engaged in constitutionally protected activity. Agency policy should therefore expressly prohibit the use of ALPR technology to monitor individuals based solely upon race, ethnicity, religion, political affiliation, participation in lawful demonstrations, or other activity protected by the First Amendment. Likewise, policies should prohibit curiosity searches, personal use of the system, or prolonged surveillance of individuals absent lawful justification.
Finally, ALPR policies should never be viewed as static documents. Both the technology and the law continue to evolve at a rapid pace. Agencies should conduct an annual review of their policies to ensure compliance with changes in state law, recent federal and state appellate decisions, emerging best practices, CJIS Security Policy updates, and advances in ALPR technology. A policy that was legally sufficient only a few years ago may no longer reflect current constitutional standards or operational realities.
Ultimately, effective ALPR programs are not built solely upon sophisticated technology. They are built upon thoughtful leadership, clear policies, meaningful training, consistent supervision, and a commitment to constitutional policing. Agencies that invest in those fundamentals will not only place themselves in the strongest legal position should their use of ALPR technology later be challenged, but they will also strengthen public trust in one of the most valuable investigative tools available to modern law enforcement.
III. Bringing It All Together
Throughout this five-part series, one theme has remained remarkably consistent. Courts have not viewed ALPR or Flock Safety technology as constitutionally suspect simply because it automates the collection and retrieval of information. Instead, they have consistently evaluated these systems through longstanding Fourth Amendment principles governing reasonable expectations of privacy, reasonable suspicion, and objective police conduct.
Just as importantly, the cases demonstrate that sound policies, meaningful training, and thoughtful supervision are every bit as important as the technology itself. Agencies that clearly define authorized uses, prohibit misuse, require officer verification, conduct regular audits, and emphasize constitutional decision-making place themselves in the strongest legal position should their use of ALPR technology later be challenged. More importantly, they reinforce public confidence that this powerful technology is being used responsibly and for legitimate law enforcement purposes.
There is little doubt that ALPR technology, and the artificial intelligence increasingly integrated into it, will continue to evolve. The law will evolve as well. As new capabilities emerge, courts will undoubtedly continue to examine how these technologies intersect with the Fourth Amendment and individual privacy rights. Until then, the constitutional principles discussed throughout this series remain the best guide for agencies seeking to balance effective policing with the protection of civil liberties.
Used properly, ALPR and Flock technology do not replace professional police judgment, rather, they enhance it. When combined with well-trained officers, sound leadership, and carefully crafted policies, these systems provide law enforcement with an extraordinarily effective investigative tool while remaining fully consistent with the constitutional principles that have long governed American policing.
