Additional Applications of Digital Image Processing to Forensic Document Examinations

Abstract

Two experimental applications of digital image processing to the examination of questioned documents are evaluated. First is a comparison of digital image processing, electrostatic detection apparatus (ESDA) processing, side lighting, and photography in the decipherment of indented writing. Best results are achieved by first utilizing the ESDA, then digitally enhancing the ESDA lift using a high-pass sharpening filter. The second application is the use of image processing equipment to make fracture match comparisons to associate carbon film typewriter ribbons with questioned typescript. Split-screen images and image overlays are found to be very effective techniques for this kind of examination. Wenderoth [1] and Baier et al. [2] have reported on image processing as it relates to questioned document examination.