Age estimation by DNA methylation in semen stains exposed to environmental conditions

Age estimation is a finding that contributes to identification in the field of forensic science. It can be used to identify the perpetrator, suspect or disaster victims and to make criminal decisions that vary depending on age. Due to the research on epigenetics and especially DNA methylation analysis giving results closer to the chronological age, estimated age panels have become open to improvement. The age estimation model by DNA methylation is a promising method with its applicability to many body fluids such as blood, saliva and semen. Semen stains are biological samples that are encountered especially in sexual assaults, can be transmitted to various fabric surfaces, and can be washed depending on the desire to clean yourself or destroy evidence. These stains may have been left in an environment for a long time or may be mixed with blood stains. In this study, it was aimed to test the semen age estimation models created by analyzing 12 CpG regions developed in the R&D laboratory of Istanbul University- Cerrahpasa, Institute of Forensic Medicine and Forensic Sciences, by exposing semen stains to environmental conditions. In this study, semen samples were taken from 3 male individuals aged 22, 32 and 44 years old. SNaPshot-based age estimation analysis was carried out after applying conditions such as fresh sample analysis, keeping the DNA in UV, adding a hematin inhibitor in the PCR phase, keeping the semen stains on different fabrics for 1 year and washing them at different temperatures. Consequently, age estimations could be obtained from the applied conditions, and except for one example, the age estimations were consistent with a deviation in the panel. These results demonstrated the durability of semen samples and the applicability of the panel to damaged biological materials.