John J. Schultz, 1 Ph.D.; Mary E. Collins, 2 Ph.D.; and Anthony B. Falsetti, 3 Ph.D. Sequential Monitoring of Burials Containing Large Pig Cadavers Using Ground-Penetrating Radar ABSTRACT: Ground-penetrating radar (GPR) was used to monitor 12 pig burials in Florida, each of which contained a large pig cadaver. Six of the cadavers were buried in sand at a depth of 0.50–0.60 m, and the other six were buried at a depth of 1.00–1.10 m and were in contact with the upper surface of a clay horizon. Control excavations with no pig internment were also constructed as blank graves and monitored with GPR. The burials were monitored with GPR for durations of either 12–13 or 21–21.5 months when they were then excavated to correlate the decomposition state of the cadaver with the GPR imagery. Overall, cadavers in sand were easily detected for the duration of this study at 21.5 months, even when completely skeletonized. Conversely, in clay it became increasingly difficult to image the pig cadavers over the first year of burial, even when they still retained extensive soft tissue structures. KEYWORDS: forensic science, ground-penetrating radar, forensic anthropology, forensic archaeology, pig cadavers The continued emphasis toward using proper forensic archae- ological techniques and methods for conducting body searches and recoveries has led to an ever-growing trend of incorporating multiple search methods (1–4). In particular, ground-penetrating radar (GPR) has proven to be a valuable search tool for forensic investigators. This equipment is now routinely used to search for buried bodies and forensic evidence, and to clear suspected areas where a body is thought to have been buried so investigations can be directed elsewhere. The increasing use of GPR with other methods for body searches is due to a number of reasons. GPR is a noninvasive search method that allows preservation of any poten- tial crime scene and buried evidence during a search. Surveying with GPR before excavating can provide forensic investigators with an undisturbed view of subsurface features so target areas can be highlighted for further testing with other search methods. Con- versely, this technology can be used as a follow-up method after using other noninvasive methods, such as visual or cadaver dog searches, to highlight the specific location of target areas for in- vasive testing. This technology has the best resolution of all the available geophysical methods used on land and depth of subsur- face features can be estimated. The data is presented in real time and results are available immediately in the field. Furthermore, a major advantage of this technology is it can be used to search for bodies or evidence buried under cement or asphalt. The application of using GPR for grave detection was first suc- cessfully demonstrated with historic and/or cemetery graves from various regions and time periods (5–8). GPR is routinely used to locate and confirm the location of hidden burials and human re- mains of homicide victims and mass graves (9–14). The success of using GPR for forensic contexts was first demonstrated with con- trolled research. These studies buried a large mammal, most often a pig cadaver that has been used as a proxy for a human body, and then detected and monitored the buried bodies with GPR for some length of time. This research has been vital in demonstrating the utility of using different geophysical instruments for locating bur- ied bodies, and to provide experience to operators searching for buried bodies. The most important and initial research was con- ducted by personnel associated with NecroSearch, a Colorado- based forensic organization (1,2,15). Geoscientists and law en- forcement personnel buried pig cadavers (an average of 70 kg or 154 lbs) to concentrate on multidisciplinary methods, including a variety of noninvasive technologies, used to detect buried re- mains. Overall, it was concluded that GPR was the most important geophysical tool used to delineate graves (1,2). However, al- though GPR was preferred for speed and accuracy over other geophysical methods, dogs, probes, intelligence, and landscape changes also contribute greatly to locating clandestine graves. Since the initial studies by NecroSearch, there have been a variety of other forensic GPR studies that have focused on regional ap- proaches in other areas of North America such as British Colum- bia (16), Tennessee (17,18), and Florida (19,20). Proxy forensic GPR studies have been very important for GPR operators because they provide them with experience in a known setting that is invaluable when they perform GPR searches in fo- rensic contexts. The presence of soil features such as clay and high fluid electrical conductivity are the major limiting factors using GPR. Therefore, since local soil features will have a significant effect on GPR performance, it is important to have controlled fo- rensic GPR studies in various areas of the county where studies test the efficacy of GPR for local conditions and environments. In addition, GPR research is important because operator experience can be a limiting factor using GPR for forensic contexts. Con- ducting a GPR survey for small and shallow subsurface objects or features that are routinely encountered in forensic and archaeo- logical surveys requires training to learn how to use the equipment and to interpret the results. A GPR survey performed in a forensic context must be a controlled survey conducted in the same manner as an archaeological investigation where GPR transects 1 Department of Anthropology, University of Central Florida, Orlando, FL 32816-1360. 2 Soil and Water Science Department, University of Florida, Gainesville, FL 32611. 3 C. A. Pound Human Identification Laboratory, Department of Anthropol- ogy, University of Florida, Gainesville, FL 32611. Received 27 Aug. 2005; and in revised form 3 Dec. 2005; accepted 10 Dec. 2005; published 21 April 2006. 607 Copyright r 2006 by American Academy of Forensic Sciences J Forensic Sci, May 2006, Vol. 51, No. 3 doi:10.1111/j.1556-4029.2006.00129.x Available online at: www.blackwell-synergy.com