Latent Fingermark Aging Patterns (Part IV): Ridge Width as One Indicator of Degradation

Abstract

This fourth article of the series is taking an in‐depth analysis at the visible aging of latent fingermarks regarding changes in ridge widths over time. The objective is to quantify and statistically describe significant ridge size variations under controlled indoor conditions. The effect of three environmental variables are examined: type of secretion (sebaceous‐ and eccrine‐rich) and type of substrate (glass and polystyrene) when aged in three light conditions (direct natural light, shade, and dark). Prior to width measurements, fresh and aged fingermarks were powdered with titanium dioxide (TiO2) and sequentially photographed at predetermined times over 6 months. Three independent observers measured the ridges from thirty predetermined locations using strategically placed intersecting lines on the print. Results indicate that fingermarks deposited on glass are more resilient to degradation compared with those deposited on plastic. The presence of direct natural light plays a negligible role on degradation compared to secretion and substrate types.

Evaluation of latent fingermark color contrast as aging parameter under different environmental conditions: A preliminary study

“…Comparing Figure 3a,b altogether, P vs. T, MI values are generally lower and more constant for tile whereas steeper slopes on plastic. This is an indication that the type of substrate also plays an important role in degradation when using this method of fingermark enhancement and color tone analysis, supporting findings from previous research [7–10]. Despite these general conclusions, the results are highly dependent on the technique used (powder color and brushing) and might not be extrapolatable to other substrates and enhancers until further research is conducted.…”

“…This research has further tested the potential use of the color contrast technique to describe aging patterns under new experimental conditions. It has also expanded previous studies that evaluate powder enhancers as possible visual indicators of the age of latent fingermarks and of the influence that the environment may have on degradation [7][8][9][10]. Two quantitative metrics (MI and IA) that were originally defined [8] as independent variables to detect changes in color tones (contrast) between ridges and furrows have been used.…”

“…For example, non‐porous surfaces (i.e., glass, plastic, metal) require specific methods for fingermark visualization and different formulations of colored powders. Research [4–10] has suggested that glass surfaces are better than plastic (polystyrene) in the “preservation” of both sebaceous‐rich and eccrine‐rich latent fingermarks after exposure to various levels of natural light (direct sunlight, shaded, and dark) once powdered with titanium dioxide (TiO 2 ).…”

“…The triad interaction between donor characteristics, environmental factors, and type of substrate have been investigated in relation to the aging of latent fingermarks [2,3]. Donor characteristics such as age, biological sex, ethnicity, and diet regimen might be as relevant as the substrate's chemical and physical properties, including porosity, wettability, and roughness [4][5][6][7][8][9][10][11][12][13]. In fact, environmental factors such as levels of relative humidity, degree of exposure to natural light, and ambient temperature have been proven to have a distinctive impact on the visual degradation of ridges of (powdered) latent fingermarks [4][5][6].…”

“…Research [4][5][6][7][8][9][10] has suggested that glass surfaces are better than plastic (polystyrene) in the "preservation" of both sebaceous-rich and eccrine-rich latent fingermarks after exposure to various levels of natural light (direct sunlight, shaded, and dark) once powdered with titanium dioxide (TiO 2 ).…”