Forensic Application of FT-IR ATR and Chemometrics to Blood Origin Discrimination

Abstract

In investigations of crime scenes, scientific analyses of biological evidences are conducted in order to identify suspects. In particular, body fluid samples are frequently collected and discrimination of body fluids is essential in criminal investigations. Recently, spectroscopic analysis methods of body fluids have been actively developed in forensic field because they are non-invasive and practically easy compared to biochemical methods currently in use. However, establishments of precise and reliable analysis methods of such complicated spectra have been challenging issues. In this study, we developed an analysis method for discrimination of antemortem and postmortem blood samples using FT-IR ATR spectra and Partial Least Squares-Discriminant Analysis (PLS-DA). In addition, we tried to discriminate blood stains using Multivariate Curve Resolution method for decomposition of substrate signals. By extracting blood signals appropriately and selection of component number in PLS-DA model, we achieved a good discrimination precision of antemortem and postmortem blood stains.