Comparison of geophysical and botanical results in simulated clandestine graves in rural and tropical environments in Colombia, South America

Abstract

Abstract In most Latin American countries there are significant numbers of both missing people and forced disappearances, c. 84 000 alone in Colombia. Successful detection of buried human remains by forensic search teams can be difficult in varying terrain and climates. This paper reports on the geophysical and botanical monitoring of simulated clandestine graves in two different environments over 24 months to establish optimal detection methods and equipment configurations. Twelve clandestine burials were simulated at three different burial depths (0.5, 0.8 and 1.2 m) commonly encountered in Latin America. The simulated targets were three pig carcasses, three human skeletons, three graves with burnt human beheaded skeletons and finally three empty graves to act as control. Geophysical detection methods included ground-penetrating radar, magnetic susceptibility, bulk ground conductivity and electrical resistivity. Geophysical results showed that apparent electrical resistivity was optimal to detect targets (85% success) in semi-rural areas and ground-penetrating radar was optimal to detect targets (92%) in tropical rainforest areas, followed by magnetic susceptibility and bulk ground conductivity. Botanical results evidenced variations in both study sites, which should be noted by forensic search investigators, with rapid growth of Raphanus in the tropical rainforest graves and Malvaceae and Petiveria in the rural study site. This paper shows the importance of conducting long-term controlled studies to assist forensic search teams with expected results and optimum equipment configuration(s).