Utilizing eDNA from bacteria, fungi, plants, and arthropods associated with mock geologic evidence for sample-to-sample comparisons and study site separation: A feasibility study

Soil and dust are commonly submitted to forensic laboratories as geologic evidence to either link an individual to a crime or to determine sample provenance. However, only the inorganic components within these materials are routinely analyzed despite evidentiary value of the biological components. Environmental DNA (eDNA) from bulk sources, such as soil and dust, can be characterized through DNA metabarcoding, where short regions of the genome are amplified and sequenced using next generation sequencing. Research on the forensic analysis of eDNA has largely been on bacterial and fungal DNA recovered from soil. In this feasibility study, we sought to determine whether DNA from bacteria, fungi, plants, and arthropods individually or in combination were stable to permit sample-to-sample comparisons between study sites regardless of spatial and temporal variables, as well as mock evidence variability. Mock soil and dust evidence was collected from two sites in Raleigh, NC (USA) over a one-year period. Using DNA metabarcoding we found that a) bacteria, fungi, and plants alone or in combination could differentiate between soil and dust mock evidence and between mock evidence from the two study sites, as the taxonomic communities were significantly different, and b) DNA recovered from plants were consistent between dust mock evidence items over the one year period. In general, total genomic DNA concentrations from soil were significantly higher compared to dust, and soil taxa were more taxonomically diverse compared to dust taxa. We also identified biases in amplification of plants, supporting the need of multiple primer pairs in DNA metabarcoding analyses to capture the full taxonomic diversity within samples. The results from this study highlight the promise of utilizing eDNA from forensic geologic materials to supplement forensic geology examinations.