Forensic Science Department, Henry C. Lee College of Criminal Justice and Forensic Sciences, University of New Haven, West Haven, CT, USA.
Department of Chemistry and Biochemistry, International Forensic Research Institute, Florida International University, Miami, FL, USA.
J Forensic Sci. 2021 Mar;66(2):719-736. doi: 10.1111/1556-4029.14635. Epub 2020 Dec 3.
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 (TiO ) 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.
本研究扩展了先前的研究，即探索粉末增强潜在指印纹脊和纹谷之间的颜色对比作为可能的老化参数。主要目的是测试该技术在预定的一组因素下的灵敏度。在这种情况下，实验因素包括两个捐赠者，他们将富含皮脂和汗腺的指印沉积在瓷砖和聚苯乙烯塑料上。这些指印在八个时间段（0-72 天）内用黑色碳或二氧化钛粉末（TiO ）开发，并在三种光照条件（直接光照、阴影和黑暗）下老化。从每个图像中收集颜色的平均强度（MI）和强度幅度（IA）指标进行统计分析。结果表明，颜色对比度受到基质、分泌物和粉末类型的显著影响，基质和粉末类型之间存在交互作用，对 MI 和 IA 指标都有影响。光照度的程度对通过两种粉末方法区分指印老化模式没有明显影响。使用回归分析，在所有光照条件下，都检测到富含皮脂的指印与其富含汗腺的指印之间存在不同的老化模式。所有富含汗腺的指印在 IA 上随时间的变化很小（或最小），而富含皮脂的样本则表现出不同的模式，从明显减少到略有增加。这些发现证实并扩展了先前关于 MI 和 IA 作为指标研究潜在指印降解模式的潜在用途的观察结果，这些模式最终可能用于估计指印的年龄。
