Farklı Yüzeyler Üzerindeki Semen Lekesi Yaşının Atr-Ftır Spektroskopisi ile Tespiti

Abstract

SOYYİĞİT, M., Detection of Semen Stains on Different Surfaces by ATR-FTIR Spectroscopy for Age Determination: A Specialization Thesis for the Department of Forensic Medicine at Hacettepe University Faculty of Medicine, Ankara, 2023 In forensic practice, the examination of semen stains is vital in the investigation of sexual offenses. Analysis of semen stains provides information not only about the identity of the offender but also about the time of the incident. Despite the fact that numerous research have employed various techniques to estimate the age of semen stains, these studies have not yet become routine practices in forensic medicine due to practical, methodological, and cost-benefit challenges. The majority of current techniques cause material recovered from crime scenes to get damaged, which prevents any essential additional analysis. In this research, our goal was to develop a useful, affordable, and non-destructive technique that would facilitate additional material investigation and be simple to use. Seven distinct solid surfaces—wood, glass, leather, tile, cardboard, metal, and plastic—likely to be encountered in interior settings at a crime scene were utilized to create semen stains. We then performed measurements using ATR-FTIR spectroscopy and chemometric analysis (PLS-DA) at different time intervals over a period of two months. Three groups of time intervals—0–24 hours, 2–6 days, and 1–8 weeks—were created for all surfaces. By chemometrically evaluating the acquired spectrum data using the PLS-DA approach, the "EFR" ratio was used to assess the method's success. The validation data demonstrated how accurately the method could group the data into the correct category. The success rate was 100% for all time intervals for wood, glass, cardboard, metal, and plastic surfaces, while for leather and tile, it was found to be the lowest at 99.94% and 99.95%, respectively. In conclusion, this study showed that ATR-FTIR spectroscopy can be used as a effective method for the identification of semen stains on different surfaces and for determining the age of the stain with the aid of chemometric methods.