Analysis of aborted fetal material using autosomal STR markers in forensic cases of sexual assault

Sexual violence represents a widespread social problem associated with serious lifelong consequences. In many cases, an outcome of sexual violence is the victim's unwanted pregnancy, usually ended in an abortion. The objective of this paper is to report five rape cases, including rapes of a minor and young woman, two incest cases and a case of human trafficking for sexual exploitation, where every case resulted in the victim's pregnancy. In each case, pregnancy was terminated in the first trimester or at the beginning of the second trimester in the relevant medical center or clinic. Fresh fetal blood or aborted tissue samples were delivered to our laboratory in order to perform paternity testing for the purpose of proving the crime. DNA extraction using Qiagen Dneasy™ Tissue Kit was optimized according to the sample type. Amplification of autosomal STR (Short Tandem Repeat) markers was performed using the PowerPlex®16 System. In two cases, mixtures of maternal and fetal DNA in the aborted fetal material were found. Using the LRmix Studio v.2.1.5 Software for interpreting DNA mixtures based on a probabilistic model, the likelihoods of maternal contribution and presence of fetal allelic variants inherited from the alleged father/suspect were calculated. Based on these results, we confirmed the presence of assumed fetal fractions (determined before software analysis) in the mixtures. In all cases, positive paternity proved the crime (probabilities of paternity >99.9999%). This cases report once again pointed out the importance of DNA analysis in the process of clarifying and solving forensic cases and demonstrated that the LRmix Studio v.2.1.5 Software can deal with complex cases such as sexual assaults.