Detection of Oral Fluid Stains on Fabric via Solution Extraction Combined with Deep Ultraviolet Raman Spectroscopy

DNA phenotyping plays a central role in modern practical forensics, yet an overwhelming amount of evidence creates significant backlogs in all major crime laboratories. A fast nondestructive test of a potential biological stain prior to DNA phenotyping should reduce the number of irrelevant samples for the analysis and increase the efficiency of the overall process. Evidence items recovered from the crime scene can often include body fluid traces, such as oral fluid (OF). This proof-of-concept study demonstrates the effectiveness of Deep-UV Raman spectroscopy in identifying OF stains on substrates such as cotton, polyester, and blue denim, commonly encountered in forensic investigations. Through spectral interpretation and statistical analysis, this study compares Raman spectra from OF extracted from substrates with pure OF spectra. Additionally, comparative analysis with near-infrared (NIR) Raman spectroscopy to deep-UV Raman spectroscopy was performed. Distinct advantages of deep-UV Raman spectroscopy were determined, including reduced sample preparation requirements and the absence of fluorescence background, enhancement of the signal-to-noise ratio, and simplified data preprocessing. Using statistical analysis methods like principal component analysis and partial least-squares discriminate analysis, differentiation between OF and non-OF samples was possible. Overall, this study underscores the versatility and potential of deep-UV Raman spectroscopy as a valuable tool in forensic science.