A Study to Explore Discriminative Power of Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy for Forensic Paper Analysis Using Decision Tree Method

Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy is one of the preferred techniques for the analysis of forensic samples. However, the potential of ATR-FTIR spectroscopy for the classification of papers has not been established and remains unclear. In this work, a total of 150 ATR-FTIR spectra of white copy paper of three different manufacturers were analyzed using two advanced statistical methods, i.e., principal component analysis (PCA) and classification and regression tree (CART). Based on simple visual examination alone, the IR spectra did not allow any definite discrimination. However, the IR spectral differences between the papers were revealed by PCA and CART methods. A region at 1500-1200 cm(-1) was determined to be the most discriminative. In conclusion, coupling of IR spectrum and CART provides a novel and non-destructive alternative for solving classification tasks in forensic context.