Preliminary soilwater conductivity analysis to date clandestine burials of homicide victims

Abstract

This study reports on a new geoscientific method to estimate the post-burial interval (PBI) and potential post-mortem interval (PMI) date of homicide victims in clandestine graves by measuring decomposition fluid conductivities. Soil water analysis from a simulated clandestine grave (which contained a domestic pig carcass) in a semi-rural environment had significantly elevated conductivity measurements when compared to background values. A temporal rapid increase of the conductivity of burial fluids was observed until one year post burial, after this values slowly increased until two years (end of the study period). Conversion of x-axis from post-burial days to 'accumulated degree days' (ADD) resulted in an improved fit for multiple linear regression analyses. ADD correction allowed comparison with two other conductivity grave studies and demonstrated it was possible to date a discovered grave and hence the victim if past local temperatures could be obtained and burial depth measured. Contemporary soil moisture sampling was also undertaken to quantify this potential variable. Research also has implications to time illegal animal burials. Further research is required to extend the monitoring period, to use human cadavers and investigate other soil types and depositional environments. NOTICE: this is the author's version of a work that was accepted for publication in Forensic Science International. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Forensic Science International, v. 198, May 2010, doi:10.1016/j.forsciint.2010 Determining PMI of recently deceased individuals have been extensively researched using a variety of methods and revisions to said methods. However, dating PMI over a longer time period or importantly the Post-Burial Interval (PBI) emplacement within a burial site is more uncertain and lacking a simple technique.This manuscript is the first to document a new and simple technique to date PMI or estimate how long a body may have been buried for using the conductivity of the decomposition fluids. Our previous FSI paper ( Jervis et al. 2009) has suggested that these fluids are the primary reason why electrical resistivity surveys work to detect the positions of clandestine burials of homicide victims. Our new suggested PBI/PMI technique, based on a two year monitoring study, is to simply measure the conductivity of decomposing fluids as we have found this has a two-step, linear relationship. Results are reinforced by comparison to another study as well as to a simulated "discovered" burial, where a ~16% error was found between the conductivity estimated date compared to the true burial date. We have also converted post-burial days into accumulated degree days (ADD) which improved the date mis-match error (to ~12%) and will...

Electrical resistivity survey to search for a recent clandestine burial of a homicide victim, UK

“…Every suspected clandestine burial site will be unique, having a different burial style and environment (eg size and associated organic content, depth bgl, wrapping, burial date and time of emplacement), soil types with varying proportions of natural and anthropogenic materials, varying soil conditions (porosities, textures, moisture content, stone content and compaction), micro-climate and associated temperature variations, vegetation, etc, which would all affect potential detection rates (see [13,26,27,[35][36].…”

“…Detection of naked targets are primarily due to conductive decompositional fluids [24][25][26] and wrapped targets due to objects restricting induced electrical ground currents (see [19,25]). …”

Collaborative Geophysical Monitoring of Simulated Forensic 'Crime Scenes’ in the U.K.

“…Accurate determination of the time since burial is also critical for forensic investigators to link suspects to or eliminating them from a crime [3]. Geoscientific methods are being increasingly utilised by forensic search teams for the detection and location of clandestinely buried material [4][5].…”

“…SOPs normally work through sequential workflows, from reviewing case information, sourcing background information and remote data analysis, before deciding upon search strategies, undergoing site reconnaissance and phased site investigations, and lastly intrusively investigating anomalous areas to give a success/failure exit strategy (see Fig. 1 and [1,3]). …”

“…These have been repeatedly geophysically surveyed by fixed-offset electrical and Electrical Resistivity Imaging (ERI) surveys as well as multi-frequency (110-900 MHz) GPR datasets at least quarterly, and every month in the first three years post-burial. Studies have been published on determining what causes relative resistivity anomalies [19], magnetic surveys [20], measurements of decompositional fluid conductivities over time [3] as well as the 0-3 years post-burial datasets [6]. Repeat surveys suggest winter surveys are optimal and resistivity surveys should be undertaken six months to two years post-burial for optimal success.…”