Challenges in contact-less latent fingerprint processing in crime scenes: Review of sensors and image processing investigations

The contact-less acquisition of untreated latent fingerprint traces with various sensing and image processing techniques is an upcoming opportunity in crime scene forensics. Current analyses of imaging sensor systems show the applicability but dependence on several factors e.g. substrate type, latent trace structure and scanning technology. Also, spectroscopy might be used on fingerprints to determine their chemical composition. Multi-sensor devices might cover huge ranges of different application scenarios. Beside single-sensor tuning and multisensor fusion approaches for quality improvement of 3D scan data for localisation (coarse scan), acquisition (detailed scan) and analysis of fingerprint traces, new challenges arise. In this article we review and summarise the current state of the art of applicable sensing and pre-processing techniques and identify 7 challenges: the need for the integration of different process models, the determination of sensor parameters, the choice of sensor types for different surfaces, the challenge posed by non-planar surfaces, the influence of dust and dirt, the age detection and separation of overlapping fingerprints and the ongoing extension of an existing benchmarking scheme [1]. Based on experiments described in this article we suggest adding the sub properties of exploited characteristic and angle tolerance to the input sensory technology property I. We show that contact-less sensors open new opportunities but also require a lot of further research for forensic usage.