Retrieving forensic information about the donor through bacterial profiling

When fingermarks are left on a surface, bacteria originating from the donor's skin are also deposited. The skin microbiome is believed to be extremely diverse between individuals, allowing for potential matching between the bacterial communities and touched objects, known as "bacterial profiling". This study stepped further and investigated how the bacterial profile could be used as an indicator of donor characteristics of potential forensic intelligence interest. Forty-five participants were asked to touch DNA-free playing cards with their dominant and non-dominant hands. Cards were swabbed and bacterial communities determined through 16S rRNA sequencing. Diversity and abundance of bacteria were compared to donor characteristics of gender, age, ethnicity, handedness, home location, sample location, occupation, diet type, use of moisturisers, use of hand sanitisers and use of public transport. Correlations between the bacterial profile with gender, ethnicity, diet type and hand sanitiser use were found. Specifically, the absence of Lactococcus indicated a primarily Chinese diet, while the absence of Alloiococcus indicated female gender, Asian ethnicity and hand sanitiser use. Testing of the prediction models demonstrated highest accuracy for gender estimation, while the prediction of other characteristics showed lower success. This study showed a correlation between the presence of certain bacterial species on donor's hands and personal characteristics of potential forensic relevance, thus demonstrating a novel application of microbiome genotyping in forensic science.