Non-contact Technologies and Digital Approaches to (Latent) Fingermark Aging Studies

Abstract

Significant developments in the field of noncontact, noninvasive surface capturing techniques have unlocked new and exciting possibilities for studying the degradation behavior of latent fingermarks. These novel technologies enable the iterative capture of specimens and thus the design and digital processing of image-based degradation time series. This chapter provides an overview of such noninvasive devices and explains the potential of three of these options: two different high-end surface measurement devices and off-the-shelf flatbed scanners. Going through the four main phases of fingermark capture, preprocessing, feature extraction, and age estimation, the benefits of these digital approaches are highlighted. They include the introduction of novel aging features based on the statistical distribution of image pixels as well as the digital computation of known aging features, such as ridge or pore size. The computation of quantitative age estimation measures provides first approximations of the quality of such approaches. As a result, fingermarks can be referred to as being fresher or older than a selected time threshold with a certain accuracy. In addition, dust deposition is shown to constitute a surprisingly promising aging feature. Although the studies presented herein can, in their current form, not be considered as being practically usable for casework or court, they highlight the potential of the noninvasive capture and digital processing for fingermark age estimations. They furthermore outline possibilities of future inquiry into this topic, by pointing out a freely available data collection as well as showing the general feasibility of off-the-shelf flatbed scanners as economical and widely available alternatives to expensive high-end capturing devices.