MEANS AND METHODS FOR IDENTIFYING INK THAT DISCOLORS IN FORENSIC TECHNICAL EXAMINATION OF DOCUMENTS

This article provides an overview of decolorizing inks and the most common pH indicators used in the production of such inks. The classification of this type of ink is characterized depending on the component composition and properties. Different ink formulations are available today, consisting of combinations of organic, inorganic and synthetic materials with different characteristics and properties (for example, thermochromic-based ink that erases when heated). The properties of such inks change depending on the light spectrum. An example is the Pilot Pen heat-sensitive gel-based ink, which consists of КРИМІНАЛЬНИЙ ПРОЦЕС ТА КРИМІНАЛІСТИКА; СУДОВА ЕКСПЕРТИЗА; ОПЕРАТИВНО-РОЗШУКОВА ДІЯЛЬНІСТЬ pigmented microparticles suspended in a translucent polymer carrier. Some methods, both destructive and non-destructive, are listed for the detection and investigation of discoloring inks. It has been noted that decolorizing inks are acid-base indicators that change color under the influence of atmospheric CO2 in the presence of air. A non-destructive research method using the Video Spectral Comparator device is separately highlighted. This device is one of the most versatile tools, which can be used using various instrumental parameters and leave the document after examination in its original state without causing damage. VSC allows an expert to detect forgery in documents due to a special built-in function of point illumination of the infrared, visible or UV parts of the spectrum, thanks to which the “disappeared” ink can fluoresce or manifest itself in another way. An example of an expert experiment conducted by foreign specialists from the Department of Forgery and Counterfeit Research of the Forensic Medical Examination Office is presented. The collaborators studied the effectiveness of certain factors on the fading of vanishing ink solutions, such as the basic substance, concentration or pH of the dye. Conclusions are made that emphasize the need to develop a practical and non-destructive method for easy deciphering of handwritten notes made with such inks.