This article contains additional content from when it appreared in the October/November issue of Forensic Magazine.

Geophysics involves the use of a variety of electromagnetic techniques that can be used to outline, discover, and plan an exhumation. This article will include applications of ground-penetrating radar (GPR), terrain conductivity (EM), thermal infrared (IR) imagery, as well as magnetometers and metal detectors. All these non-invasive¹ methods should be part of an integrated approach to getting maximum information on what lies belowground before any excavation is contemplated.

Introduction
When confronted with missing persons or apparent homicide cases, it is imperative to get an early start on their resolution. The longer an investigation is delayed, the less likely it is to be solved. Wit nesses disappear, their memories fade, as does evidence associated with a potential clandestine burial, such as odors of decomposition that would assist cadaver dogs in making a find. Small, local jurisdictions frequently do not have the manpower or expertise to pursue leads, and even less expertise on deciding how a case will move forward.

Frequently, when the potential location of a clandestine grave is determined, the first impulse by investigators is to start digging, often with a backhoe. The result of this haste is that much of the peripheral, ancillary, but supportive evidence associated with the actual burial is destroyed, either by the excavators, or the first responders on the scene. Post-mortem damage to remains during disinterment can benefit the defense in a criminal case, jeopardizing a clear conviction. You locate the body, but end up losing the case. Figure 1 shows how not to find a body—with a “forensic backhoe.”

The Technologies
One of the great achievements of modern physics was the unification of what were once disparate branches of the field.We now realize that electricity,magnetism, and radiation are all aspects of similar phenomena; interact with each other; and can be described by similar mathematical equations.That is all the technical background you need to understand what follows.²