There are several previously published studies suggesting that different people deposit different quantities of their own DNA on items they handled, so can be considered good or bad shedders. This study aimed to investigate the amount of DNA deposited on sterile plastic tubes handled by the employees in our lab for 15 seconds. In particular, we wanted to test if there are differences in the amount of DNA deposited by dominant versus non-dominant hand. Moreover, we investigated the amount of DNA deposited before, immediately after and 30 minutes after hand washing. In the end, this study compared two sampling techniques, namely wet and dry swabbing, aiming to define the technique that guarantees better recovery of touch DNA. A samples were collected from 6 individuals and analyzed for differences in DNA quantity between the two hands of the same individual, but also between different individuals and different sampling techniques. In general, our preliminary results have shown that there are no significant differences between dominant vs nondominant hand. Consistent differences were observed between individuals regarding their ability to deposit biological material on handled objects. Sampling technique was factor that significantly influenced the amount of recovered DNA, suggesting that wet swabbing recovered higher DNA amounts compared to dry swabbing. Hand washing can be considered efficient anti contaminant measure as it significantly reduces the amount of biological material deposited on handled object. Further studies are needed to confirm our findings, especially those considering quantification of DNA deposited by individuals for prolonged period of time.
DNA analysts in forensic laboratories are engaged in analysing and sampling bloodstains from bloodstained items. Detailed and precise descriptions of bloodstains on items of interest are very important for bloodstain pattern analysis (BPA). DNA and BPA reports were examined from forensic laboratories in Serbia ( N = 88). About 400 reports were observed from the past three years. First, we analysed descriptions of items (clothing and shoes) in DNA reports, and special attention was paid to descriptions of bloodstains. Subsequently, we estimated the value of descriptions of bloodstained items of interest in linking specific types of bloodstains to the obtained DNA profiles. Observed descriptions of bloodstained items in DNA reports are usually limited to phrases. A major problem exists in cases where several people were injured in the same bloodshed event. Connecting specific types of bloodstains to obtained DNA profiles is essential for the reconstruction of crime events. The complete analysis should therefore include detailed descriptions of all types of observed and sampled bloodstains. In DNA laboratories that are within a larger institute, it would be more appropriate and productive if BPA and DNA experts examined bloodstained items cooperatively. Moderately sized laboratories have a limited number of employees. So, in those DNA laboratories, it would be more appropriate to educate DNA analysts in the basic principles of BPA.
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