Evaluation of the loss of fingermark ridge clarity as a function of biological sex.

Abstract

Latent fingermark ridge patterns result from imprinting sweat secretions onto receiving surfaces. However, little is known about the loss of skin moisture between immediate consecutive depositions and its effects on the visual quality of ridges and their degradation over time. In practice, it is recurrently assumed that the first touch should contain the most residue and, therefore, display the highest ridge quality. Also, it is expected to observe a gradual decrease in the quantity of residue deposited and, in turn, in the clarity of ridges. In this study, a total of 480 fingermarks were obtained from 20 donors, 10 males and 10 females, to assess the pattern loss of ridge quality across six successive impressions in a depletion series. Black magnetic powder (BMP) was utilized to visualize and photograph fingermarks on glass microscope slides. After image standardization, Quality Scores (QS) as well as metrics on ridge clarity were obtained from the FBI's Universal Latent Workstation (ULW). Data analyses revealed a significant drop in ridge quality over the six consecutive depositions, but notably after deposition four. No differences in ridge clarity between sexes were detected within the first three depositions although an effect was noted beyond this point. ULW proved to be an excellent and sensitive tool in detecting minute changes in ridge quality across the depletion series. These results may contribute in determining the chronological order of events and support further research in estimating time-since-deposition.