Visibility enhancement and validation of segmented latent fingerprints in crime scene forensics

摘要

Forensic investigators are permanently looking for novel technologies for fast and effective recovering of latent fingerprints at a crime scene. Traditionally, this work is done manually and therefore considered very time consuming. Highly skilled experts apply chemical reagents to improve visibility of traces and use digital cameras or adhesive tape to lift prints. Through an automation of the surface examination, larger areas can be investigated faster. This work amplifies the experimental study on capabilities of a chromatic white-light sensor (CWL) regarding the contact-less lifting of latent fingerprints from differently challenging substrates. The crucial advantage of a CWL sensor compared to taking digital photographs is the simultaneous acquisition of luminance and topography of the surface, extending the standard two-dimensional image processing to the analysis of three-dimensional data. The paper focuses on the automatic validation of localized fingerprint regions. In contrast to statistical features from luminance data, previously used for localization, we propose the streakiness of a pattern as the basic feature indicating the fingerprint presence. Regions are analyzed for streakiness using both luminance and topography data. As a result, the human experts significantly save time by dealing with a limited number of approved fingerprints. The experiments show that the validation performance in terms of equal error rate does not exceed 6% even on very challenging substrates regarding high-quality fingerprints.