ISSN: 0022-1198
CODEN: JFSCA
Page Count: 10

Computer Enhancement of Evidence Through Background Noise Suppression
Dalrymple, BE
Supervisor, and Senior Forensic Analyst, Forensic Identification Services, Ontario Provincial Police, Ontario

Menzies, T
Supervisor, and Senior Forensic Analyst, Forensic Identification Services, Ontario Provincial Police, Ontario

(Received 19 May 1993; accepted 21 July 1993)

Abstract

The use of computers to enhance evidence began more than twenty years ago [1] and first came to the authors' attention in 1977 [2,3], although significant success was achieved through image processing as early as 1974. Today, affordable software packages containing many programs are available. These programs may occasionally be used to advantage on weak or obstructed evidence [4,5]. Various terms have been used to describe these procedures, including “computer enhancement” and “image processing.” An accurate description of these procedures as used by the authors would be “the optimization of signal to noise ratio.” This signal optimization is achieved largely as a result of two factors. First, the digitization of the image affords the operator far greater control over each component of the image than is possible with a photographic (analogue) image. Second, the computer has the ability to discriminate between 256 separate values of gray, from black (0) to white (255), in contrast to approximately 32 separate values perceived by the human eye. Programs of immediate utility, comprising but a small part of the software package, will be described and illustrated.

Keywords:
forensic science, digitization, computer, noise suppression, subtraction

Paper ID: JFS13627J
DOI: 10.1520/JFS13627J
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