A Single Microbial Signature Based Method for Identification of Forensically Relevant Human Biological Sample

Detection and identification of body fluids plays a crucial role in criminal investigation, as it provides information on the source of the DNA as well as corroborative evidence regarding the crime committed, scene, and/or association with persons of interest. Historically, casework methods in serology have been chemical, immunological, catalytic, spectroscopic, and/or microscopic in nature. However, most of these methods are presumptive, with few absolutely robust confirmatory exceptions. In this study, a microbiome based method was developed for the identification of the major forensically relevant human biological fluids. 904 body fluid samples (saliva, feces, venous blood, menstrual secretions, vaginal secretions, urine, and semen) were collected, preserved, extracted, and was amplified using a dual-index barcoding of the variable region four of 16S rDNA and sequenced on the MiSeq FGx sequencing platform. Results show that all major body fluid samples can be distinguished and identified with high accuracy (overall accuracy 97.6%) using the technique. Vaginal and menstrual secretions were indistinguishable from each other, and thus were classified together as female intimate samples. The proposed protocol is fast, accurate, and can be easily added into a forensic high throughput sequencing panel.