This research expands previous studies in which color contrast between ridges and furrows of powder-enhanced latent fingermarks was explored as a possible aging parameter. The main goal is to test the sensitivity of the technique across a predetermined set of factors. In this case, experiment factors have included two donors who deposited sebaceous- and eccrine-rich fingermarks onto ceramic tile and polystyrene plastic. These were developed with either black carbon or titanium dioxide powder (TiO2 ) over eight time periods (0-72 days) and aged under three light conditions (direct light, shade, and darkness). The mean intensity (MI) and intensity amplitude (IA) metrics of color were collected from each image for statistical analyses. Results show that color contrast is affected significantly by substrate, secretion, and powder types, with an interaction effect between the substrate and powder type on both MI and IA metrics. The degree of light exposure did not have a noticeable impact on distinguishing aging patterns of fingermarks by neither powder methods. Different aging patterns were detected between sebaceous-rich and their eccrine-rich counterparts for all light conditions using regression analysis. All eccrine-rich fingermarks exhibited little (or minimal) change in IA over time, whereas sebaceous-rich samples showed varied patterns, from significant decreases to slight increases. These findings confirm and expand previous observations on the potential use of MI and IA as metrics to study latent fingermark degradation patterns that could eventually be used to estimate the age of a fingermark.
Keywords: aging; carbon black; color contrast; degradation; environment; fingerprint; latent fingermark; powder; titanium dioxide.
© 2020 American Academy of Forensic Sciences.