Detection and Identification of Contaminants in Fingerprints Using Infrared Chemical Imaging

Abstract

Infrared chemical imaging has been a powerful tool in the study of digital trace evidence, especially in the detection and identification of contaminants present in those traces. After obtaining optimal conditions for collecting images and spectra, in transmission mode and in a barium fluoride window four known substances — phenobarbital, mirtazepine, caffeine and benzoic acid — were tested and detected as contaminants of fingerprints. The results were satisfactory in all cases. Mirtazepine and phenobarbital, which have a potential forensic interest, were used ina study of fingerprint blind samples in 27 volunteers. No false positives were found. The results confirm that infrared chemical imaging is an efficient technique in the detection and identification of contaminants in digital trace evidence.