Abstract:
Associative evidence is essential in investigating alleged sexual assaults involving the use of a condom. Although lubricant evidence does not have the individualizing power DNA encompasses, allegations of associations between individuals are still able to be supported or refuted. The main lubricating agent in condoms, polydimethylsiloxane (PDMS), is also included in numerous personal care products during manufacture. The existing method for lubricant analysis of an intimate swab from an alleged sexual assault is limited with regards to identifying the source. Detecting PDMS on an intimate swab suggests the lubricant may have resulted from a condom or from another source containing PDMS. The aim of this research was to determine whether PDMS-containing samples were distinguishable based on differences in their viscosity and how personal care products containing PDMS could be differentiated from condom lubricants. Fourier Transform Infrared Spectrometry (FTIR) was shown to be effective in discriminating PDMS viscosity standards and condoms of varying viscosity. Pyrolysis Gas Chromatography - Mass Spectrometry (PyGC-MS), although more sensitive than FTIR for the analysis of condom lubricants, was unable to distinguish PDMS-containing samples by their viscosity. Analysis using PyGC-MS was shown to be significantly more valuable for identifying compounds characteristic of personal care products that may aid in distinguishing possible sources of PDMS. An investigation into the persistence of condom lubricants on the penis was carried out as part of this research. Using methodology implemented for analysis of intimate swabs in sexual assault casework, condom lubricants were successfully detected on donated penile swabs up to 20 hours after condom use. Condoms are not the sole agents used to facilitate penetration in a sexual assault. In the absence of condoms, petroleum jelly may be used as an alternative lubricant. Therefore, a brief investigation into the differentiation of petroleum jelly brands through the identification of biomarkers was carried out. Gas Chromatography - Mass Spectrometry (GC-MS) analysis was used to tentatively identify key terpane and hopane biomarkers in a crude oil feedstock. Through GC-MS analysis, it was determined that terpane and hopane biomarkers were unable to be detected in the petroleum jelly samples. Recommendations were made regarding the use of PyGC-MS in differentiating condom lubricants from personal cleansing product sources for routine analysis of casework samples. In addition, future recommendations for the differentiation of petroleum jelly brands were made, with consideration given to using total ion chromatogram (TIC) analysis.