Development and validation of protocol for the identification of suspect in sexual assault cases

Abstract

In the field of forensic science, DNA genotyping is a revolutionary achievement. DNA genotyping has been greatly helpful in solving sexual assault cases. In sexual assault cases uneven ratios of sperm and epithelial cells create difficulties in the identification of perpetrator. The analysis of male and female mixed samples in sexual assault cases is a challenging task. The separation of male and female cells is a crucial step to obtain DNA profile of the male contributor. Basically, it depends on the recovery of male DNA in spermic fraction from excess amount of female and also the loss of male DNA in non- spermic fraction. There are some factors that impact in the recovery of male DNA such as the conditions of the case, time between the incident and the sample collection from victim. After that the process of sample analysis is also a very important factor and the most widely used method for the separation of male and female cells from mixed sexual assault case exhibits is differential extraction. The present study aims to develop an efficient method of differential extraction after some modifications in traditional differential extraction method. The study concluded that the results with Buffer C was with maximum recovery of male DNA with less female DNA carryover also the loss of male DNA was found minimum at 30 min incubation time. However, the success of the method depends on the type of case and the amount of male DNA which needs to be recovered. The outcome of the case is also dependent on the condition of the samples and lapse time before examination of the case. So, it is necessary to implement the additional steps according to the case and condition of the samples. Differential method is a gold standard technique which needs to be validated. In this study, the modified method is sufficient to recover the small amount of male contributor from mixed samples with the saliva, blood and vaginal epithelial cells. newline