Gpr In Forensic And Archeological Work: Hits And Misses

Ground-penetrating radar has been used successfully in the location of human<br>remains, both at archeological sites and in forensic work involving the discovery of I<br>clandestine graves. Forensic searches have occurred in subsoil burials, as well as burials<br>under concrete floor slabs. Not all investigations yield buried remains, however, and we<br>must separate out cases where bodies are not found because none is buried there, and<br>cases where the radar fails to detect the buried remains.<br>Witnesses can give faulty or misleading testimony leading to wild gooses chases in<br>otherwise credible cases. Investigators not familiar with the availability of noninvasive<br>geophysical search methods may try massive excavations that seriously disturb the<br>ground surface, and then call in someone to do GPR.<br>Physico-chemical characteristics of the subsoil can dramatically influence the length<br>of time skeletal remains persist in the ground, acid, well drained soils will cause loss of<br>identifiable remains over decades to centuries. At other sites, circulating mineral-rich<br>groundwater can impregnate the bony remains, yielding a more solid GPR target. Most<br>New England burials were made in deposits of stratified drift, which is a resistive and<br>almost ideal GPR medium; on the other hand it is an acid, well drained environment.<br>Burials using stone crypts (e.g., some 18th and 19th century US burials) will be<br>easily detected because the stone cover and an underlying air space will provide<br>dielectric contrasts recognizable on a GPR scan. Articles of clothing may also provide a<br>good GPR target when a body search is being conducted.<br>Recent clandestine burials yield near surface conductive anomalies that prevent radar<br>depth penetration below the body and appear as a signal loss whiteout. Once conductive<br>body fluids begin diffusing away, the skeleton and clothing articles provide point targets<br>that can be detected with radar.<br>Key words: ground-penetrating radar, human remains,<br>archaeology, forensics.