Key Words: Ground Penetrating Radar, Clandestine Burials, Geophysical Applications in Anthropology, Historic Cemeteries introduction and purpose

homicide victims. For forensic archaeologists this assistance may take the form of participating in the location and recovery of the victim. Schultz (2012) suggests a multidisciplinary approach and that for certain locations GPR maybe the most useful tool to apply to these searches. Noninvasive forms of search should be attempted first and certain questions should be considered before a GPR survey is instituted (Table 6). Much of the success of a GPR survey in a forensic setting can be attributed to the nature of the soil matrix in which the body was buried along with the time elapsed since burial. Factors that will limit the utility of a GPR survey are soils that may attenuate the radar energy, along time period between burial and survey, and excessive vegetation growth. Current research seeks to refine the ability of GPR to detect burials in soils that generally attenuate radar energy and to note the change though time of anomaly detection of a given burial.
Table 6. Questions to ask prior to performing a GPR survey fora forensic investigation (Schultz
2012). When did event occur How deep is body buried Was body wrapped in anything Was anything placed in grave, especially anything metallic Was anything placed over body to aid in concealment What are characteristics of site topography, vegetation, soil, etc How has area changed since burial of body Three studies from Florida display the current research conducted to better apply GPR to the detection of buried homicide victims. These studies utilized pig cadavers in a variety of burial scenarios to test the varying degree of GPR to detect anomalies in these situations through time, at differing depths, and with different antenna frequencies. This information may serve as a proxy for various types of burials associated with forensic investigations. The first study discussed hereby Schultz et al. (2006), sought to test the applicability of using GPR in a controlled setting to monitor the ability to assess anomalies in a proxy burial

situation over a length of time. The study also attempted to note to what extent depth or time of burial affected the ability of GPR detection. A total of 12 graves were monitored, each containing a fully grown pig as a proxy for the relative weight of a fully grown human. The surveys were conducted with a 500 MHz antenna throughout the process and blank control graves were included in the survey to account fora distinction between radar energy detecting soil homogenization or an actual buried body. This study found that soil had the greatest effect on GPR’s ability to detect burials overtime. For the full period of the study those cadavers buried in sandy, well-drained soils were able to be detected even at the point of complete skeletonization. This could be detected in the field and did not require significant post-processing. Alternatively, those bodies buried in clayey soils became increasingly difficult to detect overtime. Adding to previous research, Schultz (2008) attempted a similar investigation as previously discussed. 12 small pig carcasses were buried in sandy soil, six at a shallow depth and six deeper. This study examined the burials over a 21 month period using a 500 MHz antenna. As in the previous investigation, control units were dug to determine whether the GPR detected an actual burial or simply the disruption of soil from burial. At the shallow depth, all carcasses were detected at the end of the first year but became more difficult to detect towards the last two months. Moreover, these burials were largely visible with minimal post-processing. Smaller carcasses buried at a shallow depth were harder to detect due to skeletonization after a period of time and the inability of the GPR to detect an anomaly in the soil matrix. Carcasses buried deeper, however, tended to preserve longer and were thus able to be detected by GPR survey. These also required minimal post-processing (Schultz, 2008).

A third example of research into the applicability of GPR in a forensic setting is found in Schultz and Martin’s (2010) comparison of antenna frequencies in a mock burial survey situation. A large pig carcass was recorded after six months of interment using both the 500 MHz and 250 MHz antennas. It was found that the 500 MHz provided more detail of the burial, including soil disturbance than that of the 250 MHz antenna, but that both proved capable of detecting the burial anomaly (Schultz and Martin, 2010). These studies allow for the refinement of techniques used by forensic archaeologists when conducting a GPR survey in support of law enforcement agencies. Any survey undertaken has a number of conditions that may disallow the use of GPR and a sound knowledge of these limitations is necessary in order to provide proper assistance. In Florida, the use of GPR maybe hindered by excessive soil saturation, soils high in clay content, and especially vegetation. Future research may work to better offset these limitations by refining the capabilities of GPR surveys.

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