NCJ Number
187166
Journal
Journal of Forensic Sciences Volume: 46 Issue: 1 Dated: January 2001 Pages: 21-30
Date Published
January 2001
Length
10 pages
Annotation
This paper describes a method for comparing ink entries on documents stored under different light conditions.
Abstract
Various blue inks from ballpoint pens were exposed to light, both daylight (inside a laboratory close to the windows but not exposed to sunshine) and artificial light from fluorescent tubes from a short distance (about 10 cm). Normally aged ink was taken from an ordinary notebook, where all the text was intentionally written by the same pen. The text was up to 3 years old, and the notebook stored unopened and not unnecessarily exposed to light. Inks were then extracted from the document and analyzed by high performance liquid chromatography (HPLC). Significant changes in composition were noted upon exposure to light. These changes were followed by using ternary diagrams constructed for dyes generally present in blue-colored inks -- Crystal Violet, Methyl Violet, and Tetramethyl Para Rosaniline. Also, the amount of the various compounds formed by decomposition of these dyes on exposure to light was measured and used for comparing inks. These findings suggest that it is not always correct to conclude that two ink entries on different documents are different. If the differences between the ink entries are not of qualitative character, storage of the documents that contain the same ink at different light conditions might have caused the observed differences. Both optical properties (color shade, IR luminescence) and chemical composition will change, and the change occurs after rather short exposure to daylight (a few hours). The presence of various amounts of decomposition products indicates that the documents may have a different history of storage. Ternary diagrams constructed for the CV-MV-TPR system, together with plots of TPR against the total amount of decomposition products may reveal whether or not the inks can be differentiated. Many times it may be advisable to expose the investigated inks to light and follow the changes in the composition in the diagram. 9 figures and 13 references