The detection of buried human skeletal remains in the Australian environment

Abstract

Forensic anthropologists and archaeologists have been increasingly engaged, at police request, in investigations to locate and recover buried human remains ( Rodriguez and Bass, 1985 ; France et al., 1992 ; Owsley, 1995 ; Hunter et al., 1996 ). Current search methods are derived from archaeology, geology, botany, geography and taphonomy. However, there is limited testing of search techniques, particularly over graves containing human bodies, and few studies that have examined the appearance of gravesites over several years. In the absence of such studies in Australia, eight shallow burials ( six animal graves, two human graves ) and one calibration pit were established in South Australia to provide information about the physical properties of graves and the effectiveness of burial site location techniques. The findings provide descriptive information about the surface appearance of graves over six years, the chemical elements remaining in the upper levels of grave soil and the practical implications of using geophysical instruments to search for buried human remains in typical forensic cases in South Australian landscapes. Key surface indicators identified included ongoing faunal scavenging, soil surface differences, absence of moss, absence of vegetation in dry periods, the slow return of ground debris, and the formation of depressions. These were not all associated with the presence of a body but could be related to disturbance of the ground surface. There was a relationship between surface indicators and seasonal conditions and the position of the gravesites in relation to surrounding landscape features, in particular, trees. Higher levels of certain soil elements at the upper surface layer at the gravesites were identifiable after several years of burial ; in particular, calcium and magnesium were identifiable at the human body and kangaroo gravesites. Ground penetrating radar, electrical resistivity and electromagnetic induction were used to survey the gravesites. Ground penetrating radar provided the most significant results in terms of anomalies compared to the surrounds. However, use of these instruments highlighted the potential of overlooking gravesites due to lack of definitive survey data, the impact of seasonal conditions and the problems associated with using the instruments in some burial areas. Comparison of these findings is made with other international studies. Electrical resistivity surveying was successfully used to locate a 150 year old burial. A national survey on body location techniques used by police investigators in a seven year period was conducted, demonstrating a limited reported success in and use of search techniques other than ground search, implying a need to develop more reliable techniques for clandestine grave location. The results provide previously unavailable information about the surface appearance of gravesites, detectable elements in grave soil and the use of geophysical survey instruments for this purpose in South Australia.