Strategies for Potential Age Dating of Fingerprints through the Diffusion of Sebum Molecules on a Nonporous Surface Analyzed Using Time-of-Flight Secondary Ion Mass Spectrometry

Age dating of fingerprints could have a significant impact in forensic science, as it has the potential to facilitate the judicial process by assessing the relevance of a fingerprint found at a crime scene. However, no method currently exists that can reliably predict the age of a latent fingerprint. In this manuscript, time-of-flight secondary ion imaging mass spectrometry (TOP-SIMS) was used to measure the diffusivity of saturated fatty acid molecules from a fingerprint on a silicon wafer. It was found that their diffusion from relatively fresh fingerprints (t <= 96 h) could be modeled using an error function, with diffusivities (mm(3)/h) that followed a power function when plotted against molecular weight. The equation x = 0.02t(0.5) was obtained for palmitic acid that could be used to find its position in millimeters (where the concentration is 50% of its initial value or c(0)/2) as a function of time in hours. The results show that on a clean silicon substrate, the age of a fingerprint (t <= 96 h) could reliably be obtained through the extent of diffusion of palmitic acid.