Optimization of Fatty Acid Detection in Decomposition Soil.

Decomposition is the process whereby dead organisms are reduced to skeletal remains through the activity of microorganisms and soft tissue removal by arthropods and vertebrate scavengers.  During decomposition chemical degradation processes degrade macromolecules (e.g. lipids) to simpler forms of matter leading to complete disintegration of the body.  Estimating the post-mortem interval, time that has elapsed since a person has died, is essential in forensic investigations.  However, the accuracy of current methods used by forensic investigators to estimate PMI is often compromised by confounding variables.  Thus, this research was conducted to elucidate variations in fatty acid profiles throughout the process of decomposition which may correlate with the post-mortem period.  Six domestic pig (Sus scrofa) carcasses were placed on the soil surface at a Royal Canadian Mounted Police facility in Ottawa, Ontario, Canada.  Soil samples were collected within the Cadaver Decomposition Island (CDI) surrounding the decomposing remains.  A method was optimized for analyzing fatty acids in soil.  Fatty acids were extracted from soil using a heated extraction procedure in chloroform. Subsequently, the extracted fatty acids were converted to trimethylsilyl esters of fatty acids using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) to allow for detection and identification by Gas Chromatography-Mass Spectrometry (GC-MS).  A fatty acid profile was generated for each stage of decomposition to identify the fatty acids present and to determine their relative quantities.  Myristic (14:0), palmitic (16:0), palmitoleic (16:1), stearic (18:0) and oleic (18:1) acids were detected in soil containing decomposition fluid.  Overall, the level of each fatty acid was significantly greater in soil containing decomposition fluid than in control soil (p<0.001).  In particular, the level of each fatty acid was significantly greater during the bloat and active stages of decomposition. This research may be useful for increasing the accuracy of PMI estimations in forensic investigations.