Pamuklu Kumaş Üzerinde Yıkanmış Kan Lekesinin Raman Spektroskopi ve Kemometri ile Tespiti

Abstract

Bloodstains are abundant biological fluids that are encountered in crime scenes. Precise bloodstain detection on the “proof” has vitally importance for ongoing or post-commital stages. The criminal inclined to dispose the proofs that has an effect of inadequate amount of bloodstains. In case of loss in stain characteristic, the required presumptive or correlative tests can not identify the located stain with high accuracy. Twelve equal sized white %100 cotton fabrics were prepared to washing with six different cleansing solutions after creating bloodstains. The aim of the study is examining the treatment effect of each cleansing solutions for bloodstains with Raman spectroscopy. Distilled water and distilled water solutions of methanol, HCl, soap, detergent and hypochloride were used as cleansing liquids. Solutions were grouped as five sets by observing the effect of fresh solution and temperature differences as 20oC, 30oC and 60oC. Raman spectrums were collected with 785 nm laser source after all washed fabrics has been turning into dry state. For chemometrics, Raman sepctrums of different treated fabrics with bloodstains and clean fabrics were classified with PLS-DA method. MATLAB PLS_Toolbox was used for both analysis and dividing the spectrums into train and test data. The chemometric model was built with the classification parameters as sensitivity, selectivity and efficiency. Selectivity was reached to 100% for all cleansing solutions and washed fabric with bloodstains. The classificaiton has been made for distilled water with 90% sensitivity and %94.9 efficiency; for methanol solution with 96% sensitivity and 97.7% efficiency and with HCl soluiton with 91.7% sensitivity and 95.7% efficiency was calculated. Likewise, classification for soap solution 85.0% sensitivity and 92.2% efficiency; for detergent solution 100% sensitivity and 100% efficiency and lastly, for hypochloride solution 90% sensitivity and 95.11% efficiency was reached. Discrimination of different solutions and washed bloodstains on fabric was achieved with 92.7% sensitivity, 100% selectivity and 95.7% efficiency.