Quality of latent fingermark on contaminated porous surface over 1 month exposure

Recovering latent fingerprints at crime scenes is essential for establishing links between suspects and crime scenes. However, their quality and recoverability depend on various influencing factors, including sweat composition, substrate type, and environmental conditions. While much research has focused on how environmental factors affect fingermark aging, limited attention has been given to how pre-fingermark deposition substrate contaminants (hereafter referred to as pre-deposition substrate contamination) influences degradation over time. This study aims to address this gap by investigating the effect of pre-deposition soil contamination on porous substrates, specifically paper, and how this influences fingermark quality over a 28-day aging period. Paper samples were buried in soil for varying durations (1 day to 2 months) before fingermark deposition. All 90 fingermarks were developed with ninhydrin. Fingermark quality was assessed using the Centre for Applied Science and Technology (CAST) scoring system. Nonparametric statistical analyses, like Kruskal-Wallis and Friedman tests were performed to evaluate the significance of overall differences in fingermark quality between different substrate conditions and across time, respectively. The results show that while fingermarks on contaminated porous surfaces may initially appear of acceptable quality, their quality declines more significantly over time compared to clean porous surfaces. This progressive degradation suggests a synergistic effect between substrate contamination and fingermark aging, with the most severe quality loss observed on surfaces heavily contaminated prior to deposition. In contrast, control samples showed minimal changes throughout the aging period. These findings offer new insights into how a substrate’s history can influence fingermark preservation, highlighting an often-overlooked factor in evidence interpretation. The study contributes to a more detailed understanding of latent fingermark aging and has practical implications for crime scene recovery protocols and future development of fingermark aging models.