DNA recovery and human identification from semen stains washed at different temperatures

One of the most important pieces of evidence to find the suspect of a sexual assault are semen stains. It has been observed that suspects do not use condoms in many cases and transfer seminal fluids over the body of the victim, to their clothes, to bed linen, or to other objects in the environment. However, in many cases, it has been seen that the suspects or the victims tend to clean their bodies and clothes because of psychological conditions such as fear, panic, and anxiety. This study aims to determine whether human identification can be accomplished from washed semen stains by evaluating the quantity of extracted DNA obtained from washed clothes. In this study, both cotton- and nylon-blended fabrics were stained with semen samples taken from 10 volunteers and washed with detergent at 40 °C, 60 °C, and 90 °C. After stains were made re-visible using an ultraviolet (UV) light source, DNA was extracted using two different extraction methods (phenol-chloroform and spin-column). As a result, DNA extraction methods, washing conditions, and obtained DNA quantity from different washed fabrics were compared. It was shown that DNA could be obtained from all samples and that these DNA amounts could be used to perform identification. This study gives hope to the victims who have not been able to go to the judicial units immediately after the incident for fear or any other reasons and who think that they cannot get results because they have washed the laundry.