Non-destructive identification of correction pens and tapes in document fraud using ATR-FTIR and chemometrics

A significant portion of document fraud cases, often associated with organized crime, involves the manipulation of physical records using correction materials such as pen or fluids and tapes. Although these materials are visually similar, they differ in chemical composition. Fluids typically contain volatile organic solvents and pigments, while tapes consist of pigment-coated adhesive films. In this study, the ATR-FTIR spectroscopy as a non-destructive analytical technique was explored to obtain spectral data from 205 prepared samples of correction materials and visually similar substances. PCA was used for exploratory data reduction, followed by PLS-DA for supervised classification based on spectral patterns. Further, feature importance was interpreted using VIP and coefficient plots, highlighting key wavenumbers contributing to class separation. The developed models exhibited excellent performance, achieving 100% accuracy in external validation for differentiating correction materials from similar-looking substances, as well as discriminating between correction pen and correction tape samples. The findings demonstrate that ATR-FTIR spectroscopy coupled with chemometrics provides a fast, accurate, and non-destructive method for the forensic classification of correction materials, offering substantial utility in real-world document examination scenarios. Further, the spectral repository developed in this study offers a valuable reference resource for forensic document examiners, aiding in the identification of questioned materials and supporting the investigation of document forgery cases.