Investigation of the reproducibility of third-level characteristics

The process of comparing a fingermark recovered from crime scene with the fingerprint taken from a known individual involves the characterization and comparison of different ridge details on both the mark and the print. Fingerprint examiners commonly classify these characteristics into three different groups, depending on their level of discriminating power. It is commonly considered that the general pattern of the ridge f low constitutes first-level detail, specific ridge f low and minutiae (e.g., ending ridges, bifurcations) constitutes second-level detail, and fine ridge details (e.g., pore positions and shapes) are described as third-level detail. In this study, the reproducibility of a selection of third-level chacteristics is investigated. The reproducibility of these features is examined on several recordings of a same finger, first acquired using only optical visualization techniques and second on impressions developed using common fingermark development techniques. Prior to the evaluation of the reproducibility of the considered characteristics, digital images of the fingerprints were recorded at two different resolutions (1000 and 2000 ppi). This allowed the study to also examine the inf luence of higher resolution on the considered characteristics. It was observed that the increase in the resolution did not result in better feature detection or comparison between images. The examination of the reproducibility of a selection of third-level characteristics showed that the most reproducible features observed were minutiae shapes and pore positions along the ridges.