The permanence of friction ridge skin and persistence of friction ridge skin and impressions: A comprehensive review and new results.

This study addresses the permanence and persistence of friction ridges and the persistence of impressions made from these friction ridges over months and years. Permanence is the unchanging presence and appearance of friction ridge arrangements and their attributes between recurring observations of the skin. Permanence was evaluated from direct photographs of fingers collected over a period of 30-45 days (covering one or more skin regeneration cycles) as well as after 8 or more years had elapsed. Persistence embodies the operational concept of whether or not a pair of images displays sufficient similarity upon which to base an informed decision that they were made by the same finger, while acknowledging certain dissimilarities or distortions due to friction ridge physiology, image capture, matrix, substrate, and applied pressure. Persistence applies to both friction ridge skin and impressions made from these friction ridges. Permanence and persistence of skin were assessed from direct photographs of fingers taken two months apart and from finger photographs separated by an interval of at least 8 years. Permanence and persistence were also assessed from impressions taken over 4 months, as well as those separated by 8-53 years. Variability due to capture method was assessed by using four image capture methods over a four month period: direct photography of fingers, impressions captured by ink, holographic imaging, and live scan. Qualified latent fingerprint examiners assessed all changes observed over time, as well as any limitations imposed by capture method. The practice of comparison and identification of fingerprint impressions was upheld, as was the prevailing use of the word persistence to describe stability of friction ridges. All photographs and impressions of the same finger were identifiable as originating from the same source. Within all the periods of observation, level 1 detail was permanent and persistent. Persistence, but not permanence, was supported for level 2 detail. Notably, the small changes observed were only in appearance; there were no changes in the presence of new, or absence of existing, minutiae. Level 3 details of ridge edge shape and pore presence were neither permanent nor persistent. Ridge width was permanent and persistent. Incipient ridges were neither permanent nor persistent.

Latent Fingermark Aging Patterns (Part I): Minutiae Count as One Indicator of Degradation.

The authors are exploring degradation patterns of latent fingermarks over time which can be quantitatively determined in a predictable manner by visual means. Several physical degradation parameters for assessing this hypothesis are evaluated. This article analyzes the parameter "minutiae count" as a function of time. Experiment variables included were secretion type (sebaceous-rich and eccrine-rich), substrate (glass and plastic), and exposure to light (dark, shade, and direct light). Depositions were sequentially visualized with Titanium Dioxide powder over a period of 6 months, photographed, and number of minutiae recorded. Results revealed a significant decrease of minutiae for eccrine-rich marks on glass but insignificant for sebaceous-rich marks on the same surface. However, significant degradation was observed for both types of secretions on plastic. The authors conclude that the distinctive prevalence of minutiae changes over time indicates with a high degree of certainty the hypothesis is valid and deserves additional exploration.