ESDA Effects in Light of Current Discussions

Unknown parameters abound in the collection, preservation and interpretation of indented writings. One very useful method for visualizing these indented writings is through the use of electrostatic detection devices (EDD). In this paper, the instrument discussed is the Electrostatic Detection Apparatus (ESDA). The purpose of this work is two-fold. First, to develop an efficient and safe way to collect and develop impression evidence with little to no loss of reasonable and resolvable detail. Second, to provide some theoretical explanations as to the “why” of the results. Research presented here shows the effects of external factors that cause varying amounts of friction with a document, and how these effects are detrimental to the ability of the ESDA to detect handwriting impression. Some information is developed about why impressions may or may not be visualized with the ESDA whether they are visible with oblique lighting or not. A current theory of what makes writing impressions that are suitable for visualization is reviewed in light of empirical data from experiments and field observations in casework. Recent discussions of the effects of environmental factors, for instance gloves, are fit into the framework of the theory.