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What LEOs wish the public knew about ALPR technology and data usage

Automatic license plate readers (ALPRs) have proven valuable to law enforcement for many reasons, including its role in intelligence-led policing and officer safety.


ALPR data can play a pivotal role in solving crimes


By Police1 Staff

Regardless of the numerous benefits automatic license plate recognition has brought to law enforcement, the debate over ALPR and privacy concerns has been a heated one for many years. The true use and scope of ALPR technology are rarely discussed with the public.

What LEOs wish the public knew about ALPR technology

Most people don’t understand what data ALPR actually collects and what laws exist to protect the public. Here are three important things to know about ALPR:

  • Historical ALPR data can aid law enforcement in criminal investigations
  • ALPR data does not contain personal information unless combined with other data sources
  • It is well-established that there are no 4th Amendment implications in the use of ALPR

In addition, ALPR technology can only snap images of a license plate. This means the technology does not know who is driving or who is in the car. More importantly, without accessing the Department of Motor Vehicles database, there is no way to determine who owns the vehicle.

ALPR technology is not used to track individuals. ALPR technology can note location, time, and date if a plate happens to be within view of a camera, but it does not continuously follow a vehicle.

Keep these points in mind as we continue the discussion.

The Driver’s Privacy Protection Act

There is legislation to govern data use and protect the public. One of the laws that currently govern ALPR data is the Driver’s Privacy Protection Act of 1994.

The Driver’s Privacy Protection Act is a federal law that limits the occasions when state departments of motor vehicles and authorized recipients may disclose personal information contained in a person’s motor vehicle record. This includes:

  • A motor vehicle operator’s permit
  • The motor vehicle title and registration
  • An identification card issued by a department of motor vehicles

As mentioned above, the only way to link personally identifiable information — like a name, address or face — to ALPR data is to obtain access to a state’s Department of Motor Vehicle database. This is an important counter to the general fear that ALPR data makes it easy to track individuals regardless of their criminal background. Without permissible purpose, a law enforcement agency cannot access this information rendering most ALPR data anonymous.

Why LEOs should discuss ALPR with the public

Court cases and complaints about ALPR have been filed a number of times over the last few years, in several jurisdictions. In each instance, the pushback has revolved around a few central points:

  • Data can target innocent citizens
  • Data should not be stored
  • There is little or no oversight for privacy protections
  • Data is used to track individuals

The resolution of court cases, if not dismissed, has been similar. The rulings tend to cover similar bases about data preservation and investigation of secret records:

Limiting the amount of time an agency can preserve ALPR data

For instance, in Maine, there is a law that requires a purge of ALPR data more than 21 days old, and local governments have enacted similar ordinances prohibiting long-term retention of the information.

Data cannot be kept secret

In 2017, The Electronic Frontier Foundation (EFF) and the ACLU won a California Supreme Court decision that the license plate data of millions of law-abiding drivers, collected indiscriminately by police across the state, are not “investigative records” that law enforcement can keep secret.

Of course, each of these arguments or laws has consequences. This is why the community must understand the counterpoints.

The real benefits of ALPR in law enforcement

ALPR data is a technological advancement that allows officers to protect their communities more effectively.

Take for instance the Sheriff’s Department of Sacramento County. Within 30 days of having access to a national ALPR data network, they located 495 stolen vehicles, 5 carjacked vehicles, and 19 other felony vehicles. Forty-five people were arrested.

In Maricopa County, Arizona, the murderer of a sheriff’s deputy and two others were arrested after ALPR technology was used to locate the home of the suspect.

Success stories and applications are important to share with your community so they can understand its benefits and scope. Other uses include:

Predictive policing

In conjunction with other data, ALPR information can reveal patterns of activity associated with criminal events. Analysts can use data to establish probabilities of crimes and their locations. Preventive measures, community policing efforts and investigative resources can target areas most likely to be affected.

Hotlists and intelligence-led policing

ALPR system uses optical character recognition (OCR) to check the plate number against a list of “hot plate numbers” associated with crimes, child abduction AMBER Alerts, Blue Alerts, or outstanding warrants. When a match occurs, the system alerts the police and an arrest can be made.

Criminal investigations

Let’s say a rash of burglaries occurred in a city, ALPR data could be used to discover all of the license plates captured within a one-mile radius and within 30 minutes of each of these burglaries. If a single license plate is found, with permissible purpose, an office can start to combine other personal identifying factors to piece together the crime and its suspects. For instances like this, historical data is important to draw conclusions for the case.

The benefits of ALPR for the community are clear. For further reading, learn more about ALPRs and how they can help reduce crime.

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