There has been a rise in sexual assault cases where perpetrators have used condoms or lubricants. The use of condoms specifically can lead to an absence of DNA which is the primary evidence collected in sexual assaults. However, trace amount of lubricants can be transferred from perpetrator to victim. Customarily, cotton swabs in sexual assault kits are used to collect biological evidence and are then sent directly for DNA analysis. Due to the destructive nature of DNA purification, any lubricant traces can be destroyed.<br/>We are working with the Canadian Centre for Forensic Science to evaluate Raman microspectroscopy as a non-destructive screening technique for lubricants prior to DNA analysis. Verifying the presence of lubricants on swabs aids analysts in selecting the most appropriate downstream analytical methods.<br/>Approximately 35 lubricant samples (water, silicone, oil-based) were analyzed in their neat form and at two concentrations ~16,000 ppm and 500 ppm, in triplicate. The change in intensity of characteristic spectral peaks at 53, 396, 425, 1040, 1105, and 1460 wavenumbers, was recorded. While several Raman shift peaks are similar between the blank swab and simulated collection swab, the variation in the peak intensity is what can be discriminatory. Peaks indicative of these lubricant types were identified and used to create peak ratios that could indicate the presence of a lubricant on the swab. A lubricant’s presence was confirmed when a statistically significant difference existed between the peak ratios for blank swabs and the simulated collection swabs.<br/>It was concluded that the presence of lubricants can be identified on a swab using the peak ratio method, which can easily be determined for induvial case samples. This information can assist the rapid determination of the presence of lubricants, which can be used to optimize laboratory workflow and the evaluation of sexual assault evidence.

Detection of lubricants using Raman microspectroscopy and ratio comparisons

2019 Spring National Meeting

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