Title: Modelling a cadaver decomposition island to estimate time of death

Instructor: C. Sean Bohun, Faculty of Science University of Ontario Institute of Technology Canada

Abstract: Propagation of fluids from a decomposing cadaver produces a characteristic stain on the landscape known as a cadaver decomposition is- land or CDI. What is required is a model to predict how this fluid propagates through the soil and whether or not it is feasible to use as a predictor for the time of death of the cadaver.

Problem Statement: In modern forensic science the role of the soil has evolved from simply a medium that is transferred to and from a crime scene to a potential key in the investigation of decomposed remains. If a cadaver is not immediately consumed then it is subject to decomposition by insects and microbes. As this progresses, the body releases these chemical components into the soil created by (i) self digestion of the cells (autolysis) and (ii) the anaerobic decomposition of animal proteins (putrefaction). In amongst this fluid are decomposition products that can remain for extended periods trapped within the soil matrix. These materials enter the soil and provide a very local source of nutrients resulting in the formation of what is known as a cadaver decomposition island (CDI). This island is associated with increased soil microbial biomass and microbial activity. In particular, the degradation of proteins, lipids and carbohydrates will yield carbon-based, nitrogen-based and phosphorus-based products which may be retained in the surrounding soil. What is required is a mathematical model for the propagation of these fluids through the soil. Both the size of the carcass, and the environment in which the decomposition is taking place determine the total amount of fluid transmitted to the soil and the rate at which it is applied throughout the decomposition cycle. One of the fundamental questions is to determine if the propagating front of fluid within the soil can be used as a an indicator of the time of death. What is the expected concentration profile in the soil? Does the model predict a characteristic long term distribution of this material in the soil? In addition, how does the sensitivity of this technique change throughout this process? In an attempt to try to characterize the soil, some experiments have been done to the surrounding soil to characterize it’s average moisture content and permeability. Any model for the soil should be able to reproduce the patterns observed in the soil for these tests. Another wrinkle that can be added is the role of maggots in the decom- position. These organisms form localized masses that continually circulate to maintain their temperature. This constant motion also helps to move the fluid. Is this process significant in the propagation of the fluids? Can the affect of this process even be quantified?

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