Quantitative evaluation of latent fingermarks with novel enhancement and illumination

Abstract

A variety of suspended silica and metal nanoparticles have been used over the last 20 years to enhance latent fingermarks. This study quantitatively evaluates enhancement of natural and sebum-enriched fingermarks from three adult subjects acquired with a consistent applied force on glass with a fingermark press using suspended commercially available polystyrene (PS) particles. Images of the enhanced fingermarks acquired with total internal reflection (TIR), or standard overhead white light (WL), illumination are compared with fingermarks enhanced with conventional methods including cyanoacrylate fuming. The different enhancement and illumination methods are quantified based on the brightness and contrast of the fingermark images, as well as the number of minutiae that can be identified and matched to those on an inked manually acquired “template” fingermark using automatic fingerprint identification system (AFIS) software. Enhanced fingermarks acquired with the press are shown to be more consistent than manually acquired fingermarks based on these metrics. The results demonstrate that TIR illumination from a large-area illuminator built in house gives enhanced fingermark images with more matched minutiae and contrast superior to that for WL illumination for all types of enhancement. “Wet-powdering” with PS particles gives fingermark images that are for the most part comparable in terms of the number of matched minutiae to fingermarks enhanced with more conventional methods, suggesting that this novel enhancement method has a performance comparable to conventional enhancement methods. Interestingly, the age of the fingermark appears to have almost no effect on this new type of enhancement; sebum-enriched fingermarks ranging in age from 12 h to 435 days appear to have statistically identical numbers of matched minutiae.