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Q&A: How to fight crime using a virtual fence of LPR cameras

Use license plate readers to monitor key points of ingress and egress to identify suspicious vehicles and develop investigative leads

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A network of LPR cameras can be used to build a virtual fence to monitor and protect a community or geographic area. Many cities are adopting this strategy to identify stolen and suspicious vehicles and develop investigative leads.


Sponsored by Vigilant Solutions

By Rachel Zoch, Police1 BrandFocus Staff

License plate readers are nothing new, but many police agencies are not using these tools to their full potential. Major cities like London and New York have used license plate reader technology to monitor vehicles entering and exiting their jurisdictions for years. Now, smaller cities are adopting this “virtual fence” concept to identify stolen and suspicious vehicles and develop investigative leads.

This conversation with former NYPD detective Tom Joyce, now vice president of client relations for Vigilant Solutions, explores how a network of fixed LPR cameras and data can be used to build a virtual fence to protect a community or geographic area of responsibility.

What is a ‘virtual fence’?

The concept of a virtual fence is when you have a geographical boundary that you want to place a “virtual fence” around using fixed license plate reader cameras. Basically what you’re doing is saying I want to know every vehicle that enters and exits our jurisdiction. With fixed camera deployments, you will be identifying all cars entering and exiting.

How does a virtual fence help law enforcement investigate crimes?

The easiest win after deploying a virtual fence is when any car that enters into that jurisdiction is read by a license plate camera and then matched to a hot list. The FBI puts out the NCIC hot list of about 350,000 wanted vehicles twice a day. A large number of those vehicles on that NCIC hot list are high-threat vehicles such as a stolen car, fugitives, Amber Alerts, etc.

When a hot-listed license plate passes one of the LPR cameras, an alert is immediately dispatched to the police department, and they allocate resources to try and locate that vehicle. Once that vehicle is located, the officer can then take the appropriate action commensurate with the type of crime. The hot list information also enhances situational awareness – knowing the threat level supports officer safety, which is of the utmost importance.

How does a virtual fence help investigators develop and pursue leads?

Let’s say a previously unknown vehicle that is neither on the NCIC hot list nor a custom hot list enters a jurisdiction, and the occupants commit a crime and then leave. Detectives will conduct an investigation, and through canvassing, interviews and interrogations and follow-up, they will develop leads. Through one of those leads, they may get a description of a vehicle or even a partial or full license plate number.

The investigator would consider the time of the offense as reported by the complaining victim and conduct queries in the LPR platform to extract a few leads that point toward the vehicle described. They would then pursue the lead by running the license plates for registered owners, running background checks on those registered owners and associated family members – anyone who might have access to that vehicle – and start developing an investigative lead plan to identify the suspect.

When you have the virtual fence set up, you know when the vehicle entered the area – but you also want to know the time that it exited, because if there’s only one detection, that would tell you that the car is still within your jurisdiction. That information is critically important in the interview and interrogation process of the suspects and witnesses, because elements of the crime have to make sense. If the suspect’s statements are inconsistent with what the technology recorded, that gives the detective the ability to break down their story and drill into the facts.

How does a virtual fence help prevent crimes?

People use stolen cars to commit other crimes. If you can catch them “at the gate” in the stolen car, my experience tells me that there’s probably a decent percentage of occupants in those stolen vehicles that have high rates of recidivism.

You will see a percentage of those cars will have occupants that have warrants. That means they’ve been arrested and haven’t even finished answering out the offense that they’ve been charged with. Those people are very high-risk for crime. If you interrupt them before they commit those burglaries and robberies, that’s where you get your biggest impact on crime reductions.

That analogy of stopping them at the gate actually goes back to the New York City Transit Police Department in the early ’90s. None of the people who were going into the New York City subway system to commit robberies and other crimes were paying their fares. You don’t have to wait and see the robbery and catch them in the act – stop ’em at the gate.

I was part of that strategy, and a high percentage of people who jumped the turnstile either possessed firearms illegally or had warrants or were career criminals with intent to commit more crimes. The philosophy is the same with a virtual fence, only with stolen vehicles.

The ultimate goal in law enforcement is to prevent crime before it even happens, but unfortunately there are cracks in the system. Crimes will still be committed. There’s nothing more frustrating than a detective trying to solve a case and the leads aren’t there and the technology wasn’t in place and you’re working with nothing.

What are some of the impacts that a community and its law enforcement can expect as a result of using LPR virtual fence technology?

Higher crime has a trickle-down effect in so many ways: the stress and health of families in higher-crime areas, property values plummet, fewer businesses opening and thriving, the increased cost of services to respond to crimes and arrest and prosecute offenders.

There are a lot of studies that talk about the economic impact of crime, so if you can take an investment and set your city up to help mitigate those crimes and keep those crime levels down, the effect is deep and wide. It’s not just a statistical reduction of, say, robberies or burglaries year over year. There’s an economic and an emotional, quality-of-life impact on the community that’s really a lot more valuable than just that statistical reporting of the decrease in crime.

Tom Joyce retired as the commander of the NYPD cold case squad.