Estimation of the age of bloodstains on soil matrices by ATR-FTIR spectroscopy and chemometrics

Abstract

Estimating the accurate time of a crime occurred is one of the priceless information in forensics practice and for the investigation purposes. There are profuse of evidence can be found at the crime scene and each of the evidence will give an important information for the investigation purposes. In this study, the Attenuated Total Reflection (ATR)-Fourier Transform Infrared (FTIR) technique combined with advanced chemometrics method was deployed. For the purpose of determining the age of the bloodstain, two storage conditions; indoor and outdoor were set up to simulate real crime scene scenario and bloodstains on soil matrices were exposed and analyzed for selected time intervals for up to 63 days. Six partial least squares regression-discriminant analysis (PLSR-DA) models were constructed-indoor and outdoor models with 1-63 days-exhibited good performance with acceptable values of predictive root mean squared error (7.04-16.0) and r2 values (0.45-0.89), respectively. Using these models, correct classification of the aged bloodstains was calculated up to 70%. In conclusion, the multivariate analysis based on PLS-DA models indicates that ATR-FTIR spectroscopy, coupled with chemometrics provides acceptable discrimination for rapid and non-destructive determination the age of bloodstains on soil matrices in particularly for outdoor and very aged bloodstains.