Thermal Surveillance on Patrol

Have you noticed how your city or beat changes when you are not in uniform and not in a cruiser? Our FOP lodge is downtown, not too far from some of our "problem areas." Driving to a meeting in my POV and street clothes really helps me appreciate how different the world is when I'm not in uniform, driving a marked cruiser. Prostitutes give a wink and a wave as I drive by; drug dealers stand confidently on the corner as I cruise past. People act differently when they feel that the police are not nearby; they expose their true selves. How many of us have watched a car zip recklessly through traffic and thought, "If I was working, he'd be going to jail?" The catch, of course, is that he wouldn't drive like that if he knew you were a cop.

Watching for illicit behavior in criminal hotspots can be challenging, especially at night. We have to position ourselves near lights, or more commonly, drive through the area. The headlights and roar of a police engine are unique...exceeded in their "give-away" factor only by the light bar on top of the car and the reflective word POLICE on the side of the car. It's hard for us to be stealthy when we work patrol, so we miss a lot.

Since a thermal imager sees heat and does not rely on light, it can assist patrol officers with surveillance. Whether you are watching a perimeter or observing nefarious doings, the TI can allow you to see without being seen.

Keeping what's inside in, and what's outside out

TIs can be used to observe a fixed area, such as the fence around a power plant or the U.S. border with Mexico. The imagers can be aimed at key points, set up in interlacing coverage. They can also be set to rotate and cover a wider area. Then, multiple imagers can be monitored in a control room via closed-circuit TV. The advantage is that even a person wearing great camouflage and moving through the shadows is going to give off heat. Locating him with night vision could be nearly impossible; but his heat will give him away. Spotlights, of course, show the person where you are looking, which makes it easier for him to avoid detection.

Rarely do we, as the police, guard fixed perimeters. But we do set up mobile perimeters, such as when we are trying to contain someone who just robbed a store or just bailed from a stolen car. The mobile perimeter can be secured in much the same way as a fixed perimeter. One officer can cover more area, especially at night, when he uses the TI properly. By aiming headlights, spotlights and takedown lights in one direction, he can pretty much assure that the suspect will not go that direction. After all, even the stupid criminals know that running through your lights is a sure-fire way to get arrested.

But, if you aim the TI at a right angle to your headlights, you can now secure two sides of the perimeter; and the suspect will be much more likely to attempt to break through the darkened area than the lit area. Monitoring that area with the TI allows you to check for his heat signature as he bolts to presumed safety. In fact, you could set up a perimeter such that only one area is unlit, driving the suspect that way into the arms (and handcuffs) of waiting officers.

I saw you do it

You can also use a TI in the surveillance of people. Where I work, we have a high density of prostitution and narcotics activity. Since it is a Part I crime, we also are very concerned about larcenies from autos (LFAs). A thermal imager can be used to help combat all three of these activities.

While prostitutes may solicit in brighter areas, they will actually "close the deal" in dark alleys or behind dimly lit buildings. Many drug deals and LFAs occur in poorly lit areas as well. When you know the areas you want to observe, you can set up in a safe area with a thermal imager and just watch.

Again, your average criminal understands how to hide from headlights, street lights and your flashlight. He does not understand, or even contemplate, trying to hide his body heat from a thermal imager. By scanning a high crime area, you may see hookers and johns duck into the shadows of an alley, or watch a hand-to-hand drug deal in the corner of a park. You could even watch the LFA thug get ready to smash another car window to grab a stereo.

Depending on the quality of your TI, the ambient temperatures and your comfort with the device, you may or may not be able to identify key features of a suspect. Eyeglasses, beards, heavy coats and hooded sweatshirts may be discernible on a TI display. However, you and your partner will probably have to plan an approach to get up on the suspects and actually put "hands on." If your manpower and call volume allow, you could even set up an observation team and a contact team.

When the suspects profess their innocence and claim that they didn't do anything wrong, you can confidently inform them, "I saw you do it."


Night time is always a challenge for patrol officers. Poor lighting and higher criminal activity normally means we have to rely on bright lights to catch bad guys who know where we are and where we can see. By creatively deploying thermal imagers on the streets, officers can not only secure perimeters, they can also watch high-crime areas covertly. The ability to be covert with a TI gives us as officers a huge advantage, because we all know, when people think the police aren't around, they act like their natural selves. And sometimes, that's exactly what we want.