ISSN: 0022-1198
CODEN: JFSCA
Published Online: 1 January 2002
Page Count: 8

Photographic Evidence Protocol: The Use of Digital Imaging Methods to Rectify Angular Distortion and Create Life Size Reproductions of Bite Mark Evidence
Bowers, CM
Clinical Assistant Professor, University of Southern California School of Dentistry, Deputy Medical Examiner, CA

Johansen, RJ
Consultant in Forensic Odontology, Santa Barbara County Sheriff/Coroner, CA

(Received 23 December 2000; accepted 3 April 2001)

Abstract

Bite mark evidence seen in skin injuries or objects is commonly photographed for evidentiary documentation, preservation, and analysis. Distortion in forensic evidence photographs diminishes the outcome of analytical procedures available to the forensic odontologist. Inaccurate positioning of the evidence, camera, or measurement reference scale creates perspective and parallax distortion of the captured image. These variables must be eliminated, if possible, to ensure reliable results derived from comparison of the suspect teeth and the bite mark. Detection and measurement of camera/evidence/scale misalignment is the threshold step in evidence evaluation, and is possible through digital imaging methods coupled with established methods. Correction (rectification) of perspective distortion is possible through the application of additional digital editing techniques. This study establishes type categories of perspective and parallax distortion seen in bite mark evidence, validates the use of the digital imaging tools of Adobe® Photoshop® to correct certain types of distortion, and establishes a forensic protocol to verify the accuracy of evidence photographs requiring dimensional accuracy.

Keywords:
forensic science, forensic odontology, forensic dentistry, computers, Adobe® Photoshop®, digital, off-angle distortion, parallax distortion, perspective distortion, photography, digital imaging, rectification, bite mark, theta, two dimensional scale, lifesize magnification

Paper ID: JFS15221J
DOI: 10.1520/JFS15221J
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