Detection,discrimination and aging of human tears stains using ATR-FTIR spectroscopy for forensic purposes

Abstract

Body fluids such as blood, semen, saliva, and vaginal secretions are commonly encountered as biological evidences at the scene of crime. Tears are rarely encountered and largely unexplored in the forensic context. Analysis of body fluid evidence helps in establishing a link between the perpetrator, victim, and crime scene for reconstruction. Several methods exist for their identification using biochemical and serological methods. But due to their limitation as destructive techniques and low specificity, they are prone to give false-positive results. On contrary, Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy has been explored due to its ability to identify unknown substances based on their molecular structure. The present study investigated the use of ATR-FTIR spectroscopy for the detection and discrimination of tears from other commonly encountered body fluids. The study also investigated the potential of tears as an age estimation marker at the scene of crime. The results depicted that chemometric methods successfully discriminate the infrared spectra of tears from the other fluids with 100% accuracy, while the spectra of tears showed significant changes over time and the regression model showed that it can be used for age estimation at the scene of crime. The overall findings of this study can be further used in crime scene investigation after more rigorous investigation and validation under several interfering factors.

Keywords

• Crime scene investigation
• Tears
• Body fluid discrimination
• Age estimation
• ATR-FTIR
• Chemometrics