Level 3 details: the biological variability among the Chinese Population

Fingerprint evidence plays a critical role in forensic identification. While prevailing methodologies rely predominantly on level 1 (patterns) and level 2 (minutiae) features, the potential of level 3 details, involving ridge shapes and pore structures/locations has been overlooked, particularly in the case of fragmentary, distorted, or blurred latent prints. Despite their forensic significance, research on the level 3 details within the Chinese population remains underexplored. This study evaluates both the variability and distribution of level 3 details in the Chinese population. A dataset consisting of 2,000 fingerprints from 200 donors (aged 11–46 years), collected via cyanoacrylate, ninhydrin, and standard 10-print card methods, is studied. Analytical results reveal that the frequencies of incipient ridges and ridge breaks are 24.1% and 3.9%, respectively, with ridge breaks occurring most frequently on thumbs, while incipient ridges correlate strongly with whorls. Although no significant gender correlation is observed, males exhibit a higher incidence of incipient ridges. Statistical modelling confirms Poisson-distributed occurrences for both ridge breaks and incipient ridges (P < 0.01), and significant correlations are also found for intra-finger and inter-finger incipient ridges. These findings establish robust empirical baselines for level 3 details and support their integration into forensic evidence evaluation, increasing the discriminative power of latent prints.