Problems of Forensic Sciences 2015 Vol. 101 (CI) 5-13
AGE-DEPENDENT CHANGES OF CONTRAST IN FINGERMARKS OF VARIOUS LIPID CONTENT
Szymon MATUSZEWSKI
Laboratory of Criminalistics, Faculty of Law and Administration, Adam Mickiewicz University, Poznań, Poland
Streszczenie
There is no accepted method for the determination of fingermark age. In this article, the usefulness of contrast between ridges and valleys in powder-developed fingermarks as a marker of age is tested. Age-related changes in contrast were studied for three categories of marks: marks with a low, moderate and high lipid content. Marks were deposited on drinking glasses by a single donor and were subsequently aged in a temperature chamber. Aluminum flake powder was used for development and black gelatin lifter for preservation. Contrast was quantified from scanner-acquired images by using the histogram function of Adobe Photoshop. It was defined as the difference in the average intensity of pixels between valleys and ridges in a mark. Clear differences in the pattern of age-related changes in contrast were found between different categories of marks. Marks with a high lipid content revealed no changes in contrast for the whole 60-day period, whereas marks with a low and moderate lipid content showed an initial period of no-change, which was followed by an exponential decrease in contrast. The period of no-change was shorter and the rate of decrease was higher for marks of low lipid content as compared to marks of moderate lipid content. These results indicate that contrast may be considered as a promising marker of age for marks containing a low or moderate quantity of lipids.
Słowa kluczowe
Criminalistics; Fingermarks; Fingermark age.