Physical and chemical analysis of pig carcass decomposition in a fine sand
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The development and improvement of methods used for the estimation of the postmortem interval (PMI) is a common area of research in forensic science. This research was conducted to physically and chemically analyze pig carcass decomposition on a soil surface using conventional and newly developed methods for the potential use in estimating the PMI. Photographs of pig carcasses decomposing on forested and open land were scored using a decomposition scoring system and decomposition scores were related to accumulated degree days (ADD). Overall, the ADD values were significantly different for the two groups of carcasses; however, the ADD values for the onset of each score demonstrated more similarity between groups. Decomposition scoring results also indicated that refinements must be made to the calculation of ADD to allow for a meaningful comparison of pig and human decomposition. The decomposition of pig carcasses altered the water content, pH and fatty acid content of soil. The fatty acids, myristic, palmitic, palmitoleic, stearic and oleic acids were successfully extracted and analyzed from decomposition soil. Palmitic, stearic and oleic acids were the most abundant fatty acids detected whilst the levels of myristic and palmitoleic acids were negligible in comparison. A three peak fatty acid cycle was also observed for each fatty acid. Variations in soil pH and fatty acid content of decomposition soil have the potential to indicate the presence of a decomposition site. Furthermore, a nonlinear diffusion model was developed to predict the development of the cadaver decomposition island (CDI) in soil over time. The simulation of the model indicated that the diffusion model has the potential to generate PMI estimations for early stages of decomposition by corresponding the effective radius of the CDI to a particular time point. The general findings of this research indicate that more accurate methods for PMI estimations can potentially be developed with further research.