Using infrared imaging technology can help law enforcement professionals stop crime before it happens. A thermal imager measures very small temperature differences that can’t be seen by the naked eye, allowing you to see in no- or low-light situations.
It takes those images and creates an infrared picture — a picture that law enforcement can use to catch criminal behavior. That’s a powerful ability, and one that the Law Enforcement Thermographers Association (LETA) recognizes. LETA is a non-profit law enforcement association founded as an infrared training organization for law enforcement (www.leta.org). The association has sanctioned 11 infrared imaging uses for law enforcement and is reviewing more each day. Before an application can be added to the LETA list, a federal or state court must have accepted the infrared images as evidence in a case. Once it becomes part of case law, the LETA board meets to accept it as an application. The applications below are among the LETA-approved uses for infrared imaging.
Infrared imagers can be useful in detecting hidden vehicle compartments used for transporting illegal drugs, contraband or even people. Due to the change in thermal characteristics of a surface caused by an adjoining wall or bulkhead, thermal imagers highlight structural details unseen by the naked eye. New applications are emerging every day in the use of thermal imaging, both in and out of the field of law enforcement. Watch for upcoming articles in future issues of Eye on Infrared to address these applications.
In a crisis situation, one of the first operational actions is to set up a perimeter. Thermal imagers can make this perimeter more effective in containing and apprehending the suspect, or detecting and preventing unwanted intruders from invading a restricted area. Similarly, highly restricted facilities, such as correctional institutions or industrial plants, can monitor perimeters night or day with the aid of an infrared imager.
Marine and ground surveillance
Infrared imagers can be used for nighttime navigation on bodies of water to locate and track a variety of vessels. The ability of an infrared imager to see in total darkness allows investigators to conduct surveillance undetected and without violating citizens’ fourth amendment rights of privacy.
One of the earliest uses of infrared imaging in law enforcement involved structure profiles during indoor marijuana cultivation investigations. Indoor growing operations require the use of high intensity growing lamps which produce large amounts of heat. This heat must be exhausted through the building’s structure to maintain an acceptable air temperature for the marijuana plants to grow. The exhausted heat will manifest itself in several ways: through exhaust vents, attic vents and exterior walls. Infrared imagers see this abnormal excess heat and provide an additional element of probable cause.
During ground operations (particularly at night), infrared imagers can be used to locate threats such as hidden suspects, guard dogs and dangerous obstacles. Not only can an officer locate these dangers, he/she can see without being seen. In addition, infrared imagers can see through visible obscurants such as dust and dense smoke. When approaching a burning building or vehicle, an officer can quickly scan through the smoke to see the extent of the fire or to look for victims.
Disturbed surface scenarios
When a surface is disturbed or altered, the infrared characteristics of that surface are also altered, even though it may look the same to the naked eye. This principle can be applied as a nondestructive method to survey walls and floors for hidden compartments that may contain contraband. Turned earth also radiates differently than compacted soil, which allows infrared imagers to locate buried items because of the change in radiance of looser soil versus packed soil.
Pollutants such as oils, chemicals, and waste matter emit or radiate heat differently than the soil or water around them. Infrared imagers can track these pollutants back to their source. Airborne emissions from illegal night-time burning operations can be monitored; water pollutants can be traced upstream; and dump sights can be covertly monitored in total darkness, resulting in the arrest and conviction of the violators.
Aircraft-mounted infrared imagers are effective tools to enhance the safety of nighttime flight. Hazards like power lines and unlit landing sights can be easily identified with an infrared imager.
Fugitive searches and Rescue missions
Animate objects, such as human beings, are excellent radiators of heat. As a result, infrared imaging can be used in search and rescue operations to cover large areas quickly and accurately with less manpower. Searching for a person can be conducted efficiently during darkness or full sun light using an infrared imager. Infrared imagers are excellent at finding people and animals hiding in foliage because imagers see the heat radiated from the subject, not just the light reflected off of the foliage or person. By locating a fugitive with an infrared imager, officers can apprehend a subject without giving away their own location or without blind sweeps involving many officers.
A vehicle radiates a lot of heat; both during and after its use. The heat shows up not only from the engine, but also from the tires, brakes and exhaust. Using an infrared imager, a police aircraft can track a suspect’s vehicle easily from the air, even if its headlights are turned off. Likewise, a patrol car, using a vehicle mounted imager, can track a suspect’s vehicle in a crowded parking lot or remote area by detecting the heat of the recently driven vehicle.