Abstract

Due to the limited or high degree degradation of nuclear DNA (Deoxyribonucleic acid) content in some cases of sexual assault at forensic cases, successful results in standard genetic profiling techniques are not achieved. The aim of this study is with swab to characterize the male mitotype by mtDNA (mitochondrial DNA) typing from individually collected sperm cells together with physically differentiation of the perpetrator spermatozoa among the victim epithelium cells using micromanipulation technique. In this study, 10 samples of oral swabs were collected for the first step (from 5 volunteer pairs), and vaginal swabs for the second step after the sexual intercourse. In the first step, intra-oral swab specimens were analysed and the mtDNA profiles of the male and female were determined. These profiles were compared to the Revised Cambridge Reference Sequence. For each couple, SNP regions not seen in women present in men were detected. Based on these detected SNP (Single Nucleotide Polymorphism) regions, each couple’s male-specific SSPs (Sequence Specific Priming) were designed. In the second step, DNA isolation was performed by using micromanipulation technique from vaginal swab samples taken from women after sexual intercourse and sperm cells were individually collected. PCR (Polymerase Chain Reaction) was performed using SSPs designed in the first step. Then male mtDNA profiles were obtained. According to the results, the overlapping regions in relatives from the maternal side since SSP is not designed, and not able to be used in cases which relative men are involved are the disadvantages of the method. However, thanks to the micromanipulation technique used in the study, the risk of contamination is reduced and individual samples can be isolated with sperm isolation and sequenced with SSPs designed for the individual, indicating that it is a method that can be prefered in sensitive situations such as pack rape crimes involving more than one person from the same male lineage.

Key words: Forensic science, sexual assault crimes, mtDNA, SSP, single sperm cell, micromanipulation