The influence of biological sex on latent fingermark aging as examined by the color contrast technique

Abstract

This research further expands previous studies in which color contrast between ridges and furrows was examined as a possible age indicator for latent fingermarks. Here, the variable biological sex and its influence on aging were investigated. A total of 756 sebaceous-rich impressions from seven males and seven females were deposited on glass and polystyrene plastic and aged in the dark for three months. At nine discrete times, random fingermarks were visualized with a titanium dioxide-based powder (TiO2 ), photographed, and edited in Photoshop® to collect pixel color data. Two color contrast-related metrics, mean color intensity (MI) and intensity amplitude (IA), were analyzed to determine whether the aging processes of biological male and female fingermarks were equivalent. These metrics revealed that impressions from the different biological sexes behaved in a similar manner over time. However, significant effects between substrates were observed. Quadratic regression models best represented the aging trends based on the MI and IA metrics for both male and female fingermarks. The correlation coefficients (R) and coefficients of determination (R2 ) were moderate to strong for impressions on glass but weaker for plastic. These findings indicated that biological male and female fingermarks could be incorporated into a single universal age estimation model per substrate when utilizing color contrast as an age indicator. Nonetheless, future studies are needed to better understand aging processes on plastic when using this methodology and to determine the life expectancy (i.e., the potential for identification) of latent fingermarks beyond three months.