NCJ Number
186083
Journal
International Journal of Forensic Document Examiners Volume: 5 Dated: December/January 1999 Pages: 186-192
Date Published
1999
Length
7 pages
Annotation
A model is presented for the electrostatic detection apparatus (ESDA) that can detect perturbations in paper.
Abstract
An electrostatic potential models the effects of indented writing, erasures, and fingerprints. Poole-Frenkel emission from Mylar surface states is used to model the discharge process. Experimental evidence is provided to support the model. The role of the Mylar sheet is identified. The electric effect of indented writing is identified as a surface charge created by paper-to-paper friction. Various types of perturbations were studied to determine the accuracy of the model. Indented writing, erasure, and fingerprints served as examples of commonly found perturbations in paper specimens. Experimental temporal-decay data support the model. The Mylar film is essential for imaging a perturbation created by surface charge. Operating ESDA without an overlaying Mylar film does not reveal any perturbations created by friction. Without the Mylar film, the electric field is independent of the surface charge created by a perturbation. Consequently, the entire surface potential decays at the same rate without revealing an image of the perturbations. With the Mylar film, the electric field is dependent upon the perturbations, and the resulting nonuniform decay reveals an image of the perturbations. Thus, the Mylar film is essential for developing an electrostatic image of the perturbations. 1 table, 4 figures, and 18 references