Infrared Thermography Unearths Hidden Graves
Ruth A. Mendonsa
Rarely is a suspect tried for murder in a case where no corpse has been found -- a frustrating predicament when law officials believe they know the crime has been committed and who the murderer is. Homicide investigators and search specialists often need high-tech methods to find missing murder victims, and infrared thermography is proving to be a valuable tool in that effort.
EnTech Engineering's Gary J. Weil operates the Inframetrics SC1000 IR camera from a cherry picker to detect hidden graves.
The FBI, in conjunction with the Morristown Fire Fighters and Police Training Academy in New Jersey, used infrared thermography in a three-day course designed to teach crime scene investigators how to locate both recent and old hidden grave sites. It demonstrated the value and use of this technique with the Inframetrics ThermaCAM Model SC1000 infrared camera under the direction of Gary Weil, president and director of technical services for EnTech Engineering Inc. The camera allowed the investigators to examine both small and large areas with 100 percent coverage.
The group found IR thermography to be faster than any of the other techniques used in the course, including ground-penetrating radar, magnetometers and metal detectors, and it even turned up a surprise during an on-site field demonstration in an old "paupers field" cemetery. Although none of the graves was supposed to be less than 30 or 40 years old, one of them showed evidence of a recently buried body.
Grave sites contain dead air spaces caused by the body cavities or because the soil around the caskets has not collapsed as they deteriorate. The spaces act as insulation, changing the surface temperatures above the voids, because the solar energy warming the ground surface cannot enter the soil heat sink.
Undaunted by weather
During the demonstration, the weather conditions were less than favorable. The heavy cloud cover and light misting normally would have hampered the demonstration, because the infrared thermography technique usually requires about four hours of solar loading on the ground surfaces. But when the sun broke through, it took only 45 minutes of solar heating of the ground for the SC1000 to detect the grave images as they emerged from the background noise.
Just to be sure the camera was accurate, all the graves detected were confirmed by the other techniques, such as ground-penetrating radar. However, it was apparent that the camera could reduce significantly the time and money required for such an investigation.
Regarding the surprise that was encountered during the demonstration, the SC1000's Delta temperature function found one area that was much warmer than the other graves detected, indicating a more recent burial. Because the FBI is investigating this site, no more information is available at this time. We'll keep you posted.
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