Facial Recognition and Its Use by Law Enforcement

July 7, 2021

By Jill K. Sanders, Esq.

Facial recognition is a way of identifying someone using a picture of their face. Then it is compared to pictures in a database. For example, if you have an iPhone, you may use the technology to unlock your phone. Moreover, such technologies have been developed for use by law enforcement. But are there constitutional implications if police are using such programs?


How Facial Recognition Works

Facial recognition technology has four basic steps.

  1. Detection of a face: First, a camera detects and locates a face. Depending on the technology, it may even be able to detect a face in a crowd. And it can sense if the face is looking straight ahead or is at an angle.
  1. Analysis of a face: Next, the image of the face is captured and analyzed. The software will then “read” the face and identify distinguishing features of the face. For example, this could be the space between the eyes or the width of the mouth.
  1. Conversion of the image to data: After analysis, a set of digital data is prepared. In essence, the face is turned into a mathematical formula. The numerical code for the face is called a faceprint (like a fingerprint).
  1. Finding a match: Finally, the faceprint is compared against a database of other known faces.


Use by Law Enforcement

Police can use this type of technology as an investigative tool. For example, more and more crimes are being caught on camera. So, a police officer can take an image of a suspect in a crime and run it through a database to get leads.

Law enforcement can also use the technology to identify people. For instance, people who are unable to communicate – whether due to injury or conditions such as Alzheimer’s or dementia – may not be able to tell authorities who they are. Or the technology can be used to identify victims of crimes, such as those involved in human trafficking.

Use of the technology varies among police departments. And there is no standard technology used, and the size of databases may vary. For example, an FBI database includes more than 38 million face photos, including mugshots. Indeed, 2016 study found that half of American adults were in a law enforcement facial recognition database. And it’s not just mugshots that cops are using. There may also be driver’s license photos or public images, such as those posted to Facebook and Instagram.

However, there are issues with the technology. Some algorithms used have been found faulty when it comes to recognition of the faces of people of color. And there are cases of mis-identification. Old-fashioned police work of building a case based on a lead generated by facial recognition is still needed.


Laws on Using Facial Recognition Technology

Early in July 2021, Maine passed legislation restricting the use of facial recognition technology. The legislation prohibits use of the technology across all levels of state, county, and municipal government. However, law enforcement can use it where there is “probable cause to believe an unidentified person in an image committed a serious crime.” It can also be used to identify a deceased or missing person.

New York has yet to address the use of the technology by law enforcement. A recent campaign called #BantheScan is urging lawmakers to stop the use of the technology by law enforcement for the time being. The movement seeks a moratorium on its use until there is proper understanding and regulation of its use.