Forensic Uses of Digital Imaging

It happens all too often: The vague images of a poor quality video from a surveillance camera splash across the screen in a darkened courtroom and the guilt or innocence of the defendant hinges on whether or not the jury can determine if he or she is really the person in those images. Interpretation and misinterpretation of information about imaging in general, and digital image manipulation in computers in particular, by expert witnesses on both sides, and by counsel who ask questions that are both confused and confusing, may or may not help the jury in reaching a decision. Clearly there is a need for a simple guide to digital imaging for law and forensic professionals. Forensic Uses of Digital Imaging addresses that need. Written by the author of the best selling Image Processing Handbook, it shows you step-by-step how to use digital imaging to its best advantage. It explains by example when and why some procedures are appropriate and what they can be expected to reveal. While other books discuss computer programming to implement algorithms, this book shows in more simple terms just what the advantages and shortcomings of digital imaging are, and how computer image processing can be used to enhance the ability to access detail without compromising the truth of images. Practitioners will learn how to testify about their procedures and results in simple, precise language. Counsel will discover appropriate avenues for questioning to bring forth such explanations, and how to challenge witnesses who may confuse or mislead juries with wrong information or opinions.

Table of Contents:
Digital Cameras and Forensic Imaging Introduction Why go digital? Uses of digital imagery Film as a light sensor Tonal and spatial resolution, and their consequences Color response Digital photography Maintaining chain-of-control with digital images Digital video Scanners Taking good pictures Presenting pictures in the courtroom Summary Processing Digital Images Noise in digital images Noise reduction methods Median filtering Processing color images Nonrandom noise Adjusting contrast, brightness and gamma Adjusting color balance Adjusting size (magnification) Spatial distortions Other applications Enhancement Enhancement of detail Sharpening Sharpening color images Other enhancement techniques Less common processing methods Color separation and filtering Frequency space (Fourier processing) High and low pass filtering, band-pass filtering, and periodic noise Deconvolution, or removal of system defects Measuring image resolution Resolution from the Fourier transform Tonal (gray scale) resolution Detecting compression Detecting forgeries Maintaining records Identification The imaging chain Surveillance video cameras Recording and playback problems Pixels and resolution elements Noise and tonal resolution Other shortcomings Enhancement Image restoration Recognition and identification Identification of faces Identification by DNA Misdirection and mistakes The expert witnesses Working with counsel, judges and juries