Fingermark Analysis by Fourier Transform Infrared Microscopy Using Chemometric Tools

Abstract

The temporal estimation of the fingermarks deposition at crime scenes is a recurring issue in forensic identification. To study this challenging topic, a preliminary study was proposed to develop a method of fingermark analysis by Fourier Transform Infrared Microscopy (µ-FTIR), using chemometric tools for time separation in a six-day aging study. The samples were collected and analyzed at hour zero, 3 days (72 hours), 4 days (96 hours), 5 days (120 hours) and 6 days (144 hours). The samples were separated into a calibration set and a test set, using Kennard Stone. Following, a comparison between variable selection tools was made of the Ant of Colony (AOC) and the Genetic Algorithm (GA) were used with subsequent application of the Linear Discriminant Analysis (LDA). The results showed that in the analyzed samples there was a predominance of sebaceous material because of the presence of saturated esters signals, with two regions of interest in the infrared spectra, the first being 1800 - 1100 cm-1 and the second region being 3000 - 2800 cm-1. The statistical tools could group the fingermarks by donors and by age, emphasizing the separation within the tested period. More studies need to be carried out, but this work provide that µ-FTIR associated with chemometric analysis was able to separate fingermarks samples aged for up to a week.