Establishing an Agricultural Origin of Soils from Footwear Using a Soil Microbial Approach
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Forensic science describes the boundary between science and the law. Scientific evidence is often used to convict individuals of a crime or free the wrongly convicted. Forensic analysis consists of several disciplines including forensic chemistry and biology, forensic toxicology, fingerprint examination and many others. Furthermore, forensic science helps to reconstruct events through analysis of physical evidence, or evidence consisting of tangible objects. Just as the ability to associate a subject to an item of evidence can be achieved through forensic analysis of human DNA, forensic analysis of soil (or other environmental sample) DNA can be used to estimate the origin of an unknown sample or provide an association medium between crime scene samples and suspects. In an attempt to improve investigative techniques that help place an individual at a crime scene, this thesis focuses on soil microbial communities and their potential role in forensic science. In this study, source tracking algorithms that help identify the source of a “sink” (which in our case was soil collected from a shoe) were used to see whether we could link a piece of evidence to the crime scene. Given that microbes retain unique microbial signatures, these features could aid in discriminating between varying environments which a suspect has come in contact. Thus, microbial source tracking may serve as a good candidate for corroborating evidence. In addition, this study can add to existing methods used for forensic identification by strengthening the use of microbes as evidence using next generation sequencing technology. Furthermore, this microbial approach adds to the arsenal of current methods that aid forensic scientists in solving criminal investigations and can provide a better understanding of soil-derived evidence as an associative tool between an individual and a crime scene depending upon the microbial milieu that is present during evidence collection.