In the real world, we can count on crime scenes as being one thing for sure: a mess. As cops we are sent to crime scenes to sort through the pieces. Then, we are expected to put these clues together and find the perpetrator. Television and movies like to portray this as an exciting and glamorous act. In reality there is nothing glamorous behind the crime scene tape. In this article, we will take a look at the ways thermal imaging can assist in crime scene investigations.
During initial scene survey, thermal imaging can obviously help locate suspects, victims and dangers within a scene. Thermal imaging is especially helpful for this application when used in outdoor scenes where darkness or inclement weather may obscure the search. What you may not know that thermal imaging can also help you search for clues and evidence.
Once inside a crime scene, thermal imaging technology can reveal previously unnoticed details. For instance, discarded shell casings will have a different heat signature then the ground where they lie. When scanning an area, shell casings or even discarded weapons will appear white against its cooler surroundings. In the image shown, you can see that even darkness doesn't obscure this evidence when observed through a thermal imager. However, when viewed with a flashlight or just the human eye, these mud-spattered casings would likely be overlooked. Likewise, blood spatter and blood trails can show up in a similar fashion.
Using thermal imaging, we can also help determine where (or if) other people have been on a scene. Scanning furniture and seating with a thermal imager can reveal latent heat signatures, transferred from the heat of a human body to the furniture surface. Common examples of this use include a heat signature - which shows up as a white smudge or unusual white spot - on the seats of chairs or cars; a handprint on tables or glass; drag or skid marks on most any surface.
Keep in mind that you may not see a perfect handprint. Use your investigative skills and deductive reasoning to interpret what you see through a thermal imager. For example, a contacted item may appear to have a white smudge on it or it may look like white paint has been smeared or spilled on an item. This visual should act as a flag for you to take a closer look.
Another advantage of thermal imaging inside the crime scene is its ability to see things that have been altered from there original state. If a wall or floor has been changed to house a hidden compartment or ground has been disturbed, the heat signature will appear different. Once we break or saw an object, its molecular structure has changed, as well as its density and temperature. Remember to look for these things while in your scene. These items will appear slightly different than the surrounding air or ground.
As an investigator, you currently use all the tools at your disposal to collect as much information as possible about a scene. Don't forget that thermal imagers can, and should, be an important part of your evidence collection kit.
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