Examination of degradation degree of fingerprints for visualizing aged fingerprint using an ultraviolet laser

Estimating the time of fingerprint deposition at a crime scene provides clues to the duration since the crime. We have previously shown that when the fingerprint was continuously irradiated with an ultraviolet laser, the intensity of fluorescence presented just after impression decreases, and the other fluorescence appeared at longer wavelengths and its intensity became stronger over time. In this study, the possibility of estimating the elapsed time was examined using the aging function originally proposed by the research group of University of Amsterdam. Fingerprints were stored for up to two years, and fluorescence spectra were periodically measured by excitation with the ultraviolet laser, to calculate the aging rate of the aging function as dividing the former fluorescence intensity by the latter one. As a result, the aging rate were shown to increase in the order of greater UV influence and higher humidity. Furthermore, aged fingerprints were visualized using a fluorescence peak that increases with time.