Recent advances in the identification of vaginal fluid for forensic applications

Identification of body fluids in forensic investigations is important for three main reasons: first, the type of body fluid present at the crime scene may indicate the nature and context of the crime; second, one may predict the likelihood of getting quality DNA; and third, it may help to verify or discredit the statements from the victim or suspect. Vaginal fluid (VF) is a common body fluid found at the crime scene in sexual assault cases and is usually found mixed with other body fluids like semen, saliva, and blood. Methods for identifying VF are limited compared to those for blood, semen, and saliva. The existing cytochemical methods for VF detection are destructive and have low sensitivity and specificity. Examination of VF samples using spectroscopic techniques such as Fourier-transform infrared spectroscopy, fluorescence spectroscopy, and Raman spectroscopy has revealed unique spectral properties. However, identifying VF with these techniques is complicated, especially when it is mixed with other body fluids. Specific proteins unique to VF have been identified through proteomic studies. New methods to detect microbiome, DNA methylation, and RNA profiles specific to VF are being developed. Although these methods hold promise for correctly identifying VF traces at crime scenes, challenges such as high cost, complex data interpretation, and limited robustness remain. Further research to integrate chemometric algorithms, simplify workflows and develop robust methods is extremely important. Developing methods to identify and detect VF traces that are quick, reliable, non-destructive, and adaptable to existing forensic workflows is the need of the hour.