L¿INDIVIDUAZIONE E LA CARATTERIZZAZIONE DEI SITI DI OCCULTAMENTO DI RESTI UMANI IN AMBITO FORENSE: APPLICAZIONI GEOPEDOLOGICHE E GEOARCHEOLOGICHE

In a forensic scenario one of the most complex situations is the search for buried human remains, which in Italy is often tied to cases involving organised crime. The burial of a body has an impact on the environment directly above and around the area in which the grave has been excavated. If the environmental alterations can be recognized and interpreted correctly they can supply information regarding the site of burial and location of the body. The study was performed in order to establish the impact that a disturbance, due to the excavation of a grave, and to verify the interaction between a buried, decomposing body and the environment directly above and around the area of the burial due to its presence. The following study was conducted in the Ticino National Park in Lombardy, northern Italy. The chosen area for the study is of alluvial origin and characterized by the presence of a medium gravel to sand sediments covered by a very thin layer of organic topsoil. Two sub areas were singled out for the burial of 11 pigs, deceased for reasons not related to the study, weighing between 48 and 90 kg. The sub areas are adjacent to one another and have been denominated area A and area B. Area A corresponds to a small clearing in the woods with a grassy surface. Area B is a wooded area of which the surface is made up of a layer of decomposed foliage with scarce undergrowth. In each of the two areas, with the help of a small excavator, 6 pits were dug of which 5 were actual burials and 1, for purposes of comparison, was left empty apart from a metal plaque placed in the bottom that served as a target during the georadar survey. All but one of the burials in area A were single, whereas two subjects were placed in one of the pits to simulate a double victim clandestine grave. All of the burials in area B were single. The burial of all subjects in both areas was carried out in the spring of 2009: in area A all 6 individuals were buried at a depth of approximately 100 cm (pigs 1, 2, 3, 4 and 5 which were punt in the same grave, and 6), in area B 5 individuals were buried at a depth of approximately 80 cm (pigs 7, 8, 9, 10 and 11). The subjects were buried at two different depths in order to create a realistic scenario in the wooded area B. The presence of tree roots obstructed the digging of a grave beyond a depth of 80 cm, and therefore this level was not exceeded. The depth of burial in area A amounted to 110 cm. The exhumation of the carcasses in both areas was programmed at fixed intervals: the first after a period of 7 weeks in both Areas , the second after a period of 29 weeks in Area A and 35 in Area B, the third after a period of 56 weeks in Area A and 54 in Area B, the fourth after a period of 102 weeks in Area A and 103 in Area B and the fifth after a period of 130 weeks in Area A and 128 weeks in Area B. The surface above and around the burial was periodically monitored with a view to verifying alterations, both in the morphology of the surface and the re-colonization of the vegetation directly above the grave. The subterranean observation of the burials was monitored by means of ground penetrating radar (GPR), the chosen instrument being a Pulse Ekko Pro. Geophysical surveys were carried out on all burials before the trial started, a week after the deposition of the animals and subsequently, shortly before each of the exhumation dates. The exhumed corpses of the animals were finally subjected to autopsy in order to define the various degrees of decomposition during the entire period of the project according to the ADD method (Accumulated Degree-Days). Regarding the macroscopic aspects of the graves in the grassy area A, results demonstrate that also after a longer period the surface presents signs of disturbance and the graves remain visible to the naked eye. This is due mainly to the fact that the repopulation of the vegetation in and around the graves progresses in a non-intensive manner. The scenario in the wooded area B is quite different. Just one month after the burial of the animals the surface presents a uniform appearance due to the continuous coverage of leaves shed by surrounding trees that make the graves and the original surface from which they were cut. Results show that the GPR technology can clearly detect an anomaly within the deposition site during all the experimental period; the depth of the sites seem not to be relevant for the their detection, probably because the burials occur within sediments with the same origin. The decomposition proved to modify the detectability of the anomaly, as pointed out by the correlation existing between ADD score from each sample and the corresponding evidences provided by GPR. The difference in volume identified by means of GPR appears to be proportionate to the process of decomposition of the subject. The consistent loss of fluids and the re-compaction of the backfill of the grave lead, eventually, to the almost complete loss of a geophysical signature. The study has therefore demonstrated that geophysical tools may provide a useful indication for detection of burials; the need for a multidisciplinary approach to the search and recovery of buried corpses has been stressed as well. The next studies should focus on the subjective interpretation of the GPR report and the detectability of burials.