The evaluation of latent fingerprints exposed to different snow conditions and their usability in forensics

Second level dactyloscopic markants (minutiae) are irregularities in the course of the friction ridge skin used for personal identification because of their high variability. Individual uniqueness is affected by the high number of minutiae and their random distribution within the friction ridge skin. The combination of various environmental factors, e.g., snow, soil environment, and direct sunlight, can affect the quality of fingerprints. The aim of this study was to analyze the influence of snow under two different conditions (natural snowfall and immersion in the snow) within various time intervals on fingerprints. A total of 265 groomed latent distal fingerprints were taken from a Caucasian male from Slovakia. Latent fingerprints were taken only from one participant, as the composition of sweat, i.e., the sweat-fat substance, varies from person to person, which could influence the results. Subsequently, obtained latent fingerprints were developed using small particle reagent. We evaluated the decrease in the number of minutiae on latent fingerprints exposed to the destructive influence of snow. The results confirmed that snow has a significant effect on the quality of latent fingerprints, as a decrease in the average number of minutiae on latent prints was observed after only 2 h of exposure to snow conditions. After snow exposure, usable fingerprints for identification decreased, whilst non-usable ones increased, with 53.33% of non-usable fingerprints resulting from natural snowfall exposure. After exposure of latent fingerprints to snow immersion, 98.13% of non-usable fingerprints were found. The results can help improving personal identification efficiency. Key Points  Fingerprints exposed to various environmental factors are recommended to be evaluated.Visual quality of latent prints decreases with the length of exposure to snow conditions.The average number of minutiae decreases significantly after the influence of snow conditions.Snowfall has a less negative influence on the average number of minutiae than forcible immersion.Latent fingerprints exposed to snowfall have better identification potential.