NCJ Number
236607
Journal
Forensic Magazine Volume: 8 Issue: 5 Dated: October/November 2011 Pages: 25-28
Date Published
November 2011
Length
4 pages
Annotation
This article presents applications of ground-penetrating radar (GPR), terrain conductivity (EM), thermal infrared (IR) imagery, as well as magnetometers and metal detectors as non-invasive methods to be used in an integrated approach for obtaining maximum information on what lies below ground before any excavation is contemplated.
Abstract
GPR was developed to allow individuals to see behind, below, or through otherwise solid, impenetrable objects or surfaces. This technique is particularly useful when excavation is either impossible, as in frozen ground, or when excavation would be inappropriate or destructive. EM operates by generating a pulsating, three-dimensional magnetic field from a transmitter, which penetrates the ground. Once the ground is magnetized, it generates an electrical field that in turn induces a magnetic field. The new magnetic field is then picked up by the receiver and can be recorded on a data logger. Later processing can locate and map anomalies that are consistent with burials. Magnetics and metal detectors measure deviations from the earth's magnetic field at points along the survey. Standard off-the-shelf metal detectors are useful in finding shallow non-ferrous and steel metal targets such as shell casings, slugs, or even weapons. These tools would be brought in early in a clandestine grave investigation. Limitations are their shallow range and their location of other metallic debris unrelated to the burial. They should be used in conjunction with magnetometers or EM units as the need arises. IR thermal imagery is useful for scanning large areas that could not reasonably be surveyed with other geophysical methods. Once thermal anomalies are detected, they can be scanned with GPR. Geophysical investigations involve a science of differences (anomalies) in the data collected. A skilled operator of the aforementioned technologies can identify anomalies in subsoil that are not perceptible to the untrained eye. 6 figures and 2 references