Photography: Marks, Impressions, and Documents

Abstract

Photographic and optical enhancement of physical evidence is an important criminalistics function. It provides nondestructive methods of improving the visualization of evidence to allow further forensic examination. The key concepts and techniques involving optical, photographic, and digital imaging techniques are examined in this section. Critical foundation aspects found in quality forensic photography such as maintaining the dimensional integrity of evidence and the representation of scale are described to ensure forensic photography principles. Attributes required for optical enhancement including the relationship between the spectral distribution of the light source, the spectral properties of the specimen, and spectral sensitivity of the recording media are unpacked and provide a theoretical basis. Optic enhancement techniques such as absorption, reflection, transmission, and photoluminescence modes are discussed with samples illustrating those optical effects. Digital imaging enhancement techniques to increase the contrast and the modification of color using Adobe Photoshop™ are explained.