Assessment of the link between evidence and crime scene through soil bacterial and fungal microbiome: A mock case in forensic study.

In forensic studies, soil traces can be used to find clues to the origin of an unknown sample or the relationship between a crime scene and a suspect and can provide invaluable evidence as they frequently adhere to objects, with high persistence. In this study, it was aimed to investigate the potential of the bacterial and fungal microbiome diversity of the soil to be used as legitimate evidence in the resolution of homicide cases. Within the scope of a mock homicide case scenario, a total of 12 soil samples were collected, including two evidence samples, three crime scene samples and seven non-crime scene related control samples. Both bacterial and fungal microbiome profiles of these samples were analysed using Illumina NovaSeq platform. The resulting sequences were analysed using QIIME 2 microbiome bioinformatics platform. Beta diversity analysis was performed to determine the difference between samples. In bacterial community analyses, it has been observed that it is difficult to distinguish evidence samples and crime scene samples from control samples at phylum and class level, whereas differentiation could be made at genus and species level. Fungal community analyses allowed to distinguish evidence samples and crime scene samples from control samples at both phylum and class and genus and species level. Principal coordinate analysis (PCoA) results showed that distance between evidence samples and crime scene reference samples was closer to each other than non-crime scene related control samples. The results of this study showed that bacterial and especially fungal DNA in soil has the potential to contribute effectively to the resolution of forensic cases. Thus, it has been understood that it is possible to establish a relationship between the case and the crime scene with the help of microbiome analyses on soil samples obtained in homicide cases.