On the impact of DNA extraction procedure on the recovery of condom evidence

On the international level, different protocols exist for sampling condom traces, similarly to DNA traces. Usually collected with cotton swabs, some protocols use nylon swabs, which were found more efficient for the desorption of DNA, because they offer a better desorption of the compounds during the extraction. In addition, not all the protocols do contain swabs for other evidence than DNA. Depending on the protocol, the forensic scientist will either benefit from a swab purely dedicated to condom evidence or will have to prioritize which evidence to analyse first. It is more likely that priority will be set to DNA, but in the eventuality that no DNA would be recovered, it is necessary to know whether the swab can still be used for condom evidence recovery or not. This work aimed to use Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS-FTIR) to investigate whether DNA extraction affects the recovery of condom traces. Traces were simulated by either rubbing condoms on the swabs or soaking the swabs in solutions containing different concentrations of polydimethylsiloxane (PDMS), the most common condom lubricant found on the market. DNA extraction was found to generate a loss of silicones, when processed prior to condom silicone extraction. Therefore, results show that protocols should contain cotton swabs dedicated to condom traces collection.