Chapter 17 Using Soil and Groundwater Data to Understand Resistivity Surveys over a Simulated Clandestine Grave John R. Jervis, Jamie K. Pringle, John P. Cassella and George Tuckwell Abstract Geophysical electrical resistivity surveys have been used in a number of attempts to locate clandestine ‘shallow’ graves, based on the valid assumption that a grave may represent a contrast in the electrical properties of the ground compared to ‘background’ values. However, the exact causes of measurable geophysical signals associated with graves are not well understood, particularly for electrical methods. In this study, soil and groundwater samples have been obtained from a simulated grave containing a domestic pig (Sus domestica) carcass, in order to bet- ter understand how the presence of a grave may influence the bulk electrical prop- erties of the soil. This information is used to explain observations based on repeat resistivity surveys over a period of 6 months over a second simulated grave at the same site. An area of low resistivity values was observed at the grave location in the survey data obtained from 4 to 20 weeks post-burial, with the grave being difficult to identify in survey data collected outside of this interval. The low resistivity grave anomaly appeared to be caused by highly conductive fluids released by the actively decomposing carcass and this is consistent with the relatively short timescale dur- ing which the grave was detectable. It is then suggested that the most appropriate time to use resistivity surveys in the search for a grave is during the period in which the cadaver is most likely to be undergoing active decomposition. However, other authors have observed low resistivity anomalies over much older graves and it is possible that, for graves in different environments, other factors may contribute to a detectable change in the bulk electrical properties of the soil. J.R. Jervis(* ü ) and J.K. Pringle Applied and Environmental Geophysics Group, School of Physical Sciences and Geography, Keele University, Staffordshire ST5 5BG, UK e-mail: j.jervis@epsam.keele.ac.uk J.P. Cassella Department of Forensic Science, Faculty of Sciences, Staffordshire University, Stoke-on-Trent, Staffordshire ST4 2DE, UK G. Tuckwell Stats Limited, Porterswood House, St. Albans, Hertfordshire AL3 6PO, UK K. Ritz et al. (eds.), Criminal and Environmental Soil Forensics 271 © Springer Science + Business Media B.V. 2009