Fingermark ridge drift: Influencing factors of a not-so-rare aging phenomenon.

Fingermark ridge drift is a random modification of (aged) fingermark patterns at a ridge scale. This phenomenon was previously proven to alter key elements used for identifications, such as the appearance of minutiae. Little is currently reported on the underlying factors contributing to its occurrence. The present study was designed to investigate further the variables of a previous study by including a total of 768 fingermarks from a male and female, two substrates (glazed ceramic tile and plastic), two distinct color powder developers (carbon black and titanium dioxide), three indoor lighting conditions (direct natural light, shade, and darkness), and two secretion types (sebaceous- and eccrine-rich). Fingermarks were aged for 2-72 days, powdered, photographed, and drift detected by three independent observers. All aged fingermarks (672) were compared relative to fresh fingermarks (96), and ridge drift was observed in 42 of 672 (6%) fingermarks, while 168 (25%) were reported as indeterminate results. While ridge drift was detected in multiple fingermarks across all independent variables, statistical analysis using a multinomial logistics model showed that only powder type, secretion type, and the substrate indicated a significant correlation with increased incidences of this phenomenon. There was no significant correlation with the donor, time since deposition, or the environmental lighting conditions used. The highest incidence occurred when carbon black powder was used on a plastic substrate (>10%). The average observation of ridge drift is 6% of samples supporting that this phenomenon is not a rare event, particularly considering the conservative analysis approach implemented.