Reconstruction of chemical fingerprints from an individual's time-delayed, overlapped fingerprints via laser-induced breakdown spectrometry (LIBS) and Raman spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a method for atomic emission analysis that can be used to analyze the chemical composition of samples in the forensic investigations. The combined effort of extracting, analyzing, and restoring latent fingerprints at crime scenes is an important step toward successful arrests, and hence, the purpose of this research is to estimate the temporal sequence at which a fingerprint was imprinted from an individual. The difference in the laser spectrum from a latent fingerprint at times from 0 to 60 min after it was left was analyzed using LIBS and Raman spectroscopy, both of which require no chemical pre-treatment of the sample. We found that the signal intensity changes with time, 60 min after the imprint was made for the wavelengths of CN band, fatty acid, amino acid, and oil components. Based on these preliminary findings, the chemometric analysis was performed on the spectrum data obtained from 60 min of exposure time and the time-sequenced overlapping fingerprints were distinguished, which were imprinted at intervals of 10, 20, 30, and 40 min using SIMCA and PLS-DA classification methods.