Characterizing Microbial Assemblages as Trace Evidence as Following Residential Burglaries
Jack Gilbert, Jarrad Hampton-Marcell, Kyle Roebuck, Neil Gottel, Lauren Cralle, George Duncan, Jose Lopez
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This research has built upon former work entitled; “Evaluating the Skin Microbiome as Trace Evidence” and built and extended its premise which is; the microbiome can be an important tool in the forensic scientist’s toolbox. This research has shown several points including that unique and identifiable taxa may be identified back to a particular individual, that individual being the possible burglar or entrant to the crime scene. This then implies that crime scene individuals in the future MUST protect a crime scene from contamination by police, crime scene personnel, and others who might have entered the scene later after the crime has occurred. It has also been shown that further work needs to be done including identification of the bacteria which could NOT be identified as there represent a rare event or part of an individual’s microbiome. This research has significantly lowered the bar ahead since it has involved data gathered by mock crime scenes which mimic real-time crime scenes. The first question which crime scene personnel ask is how much impact is made by the individuals entering a crime scene and using their hands to touch objects within the crime scene? A second question is how unique is the individual microbiome can be traced back to an individual? The third question they ask is how long can this microbiome from an individual last at the scene? These questions have been addressed in the research.
Bacterial cells and their inherent genetic and taxonomic signatures are more likely withstand decomposition and degradation by the environment (temperature, sunlight, moisture etc) compared to residual human biological material. This may result from the bacterial cell wall or vegetative bacterial phases which can protect their hereditary material. Therefore, when microbial oligotypes which assist in individual identification can be reliably determined at each crime site, this valuable information can be applied to forensics applications in conjunction with more traditional methods. As demonstrated in this study, sampling for microbes with the routine swab method is not too onerous and relatively inexpensive (sans DNA sequencing), and probably should be included at most crime scenes. Sequence and statistical analyses of microbial 16S rRNA sequences would require an advanced level of trained personnel, or could be funneled to a central data processing center or expert collaborators.