Forensic Digital Imaging

• Acquisition of routine crime scenes using digital devices rather than traditional analog film
• Digital cameras almost totally replaced traditional film photography
• Scanners are used to digitize documents for storage and processing
• Extracting information from surveillance digital video recorders or digitizing analog video

Why Digital

• Immediacy and lower cost
• Permits computer identification and classifications of objects such as AFIS
• Instant transmission anywhere
• Archival and duplication without degradation
• Enhance images and extract and reveal details that may not be seen in the original
• Digital images can be used to bring into the courtroom evidence such as DNA identification by electrophoresis
• Build walkthroughs to help jury keep track of crime scenes

Digital Cameras

Consumer models:

• Unsuitable for forensic applications
• Poor optics that cause image distortion and vignetting
• Inability to adjust exposure setting (shutter speed and aperture) and focus
• Built-in flash only
• Lack of tripod socket
• Images stored in compressed format (JPEG)

Taking Good Pictures

• Take pictures that reproduce the details of the scene, evidence, surface markings, etc..
• Separate pictures are needed to capture different parts of the scene with separate exposure settings and different scales.
• Place a reference scale close to objects that will be used as evidence.(ruler with clear legible markings.)
• Place color reference if color is important
• Take perpendicular pictures if size, shape, spacing of object is important (footprints, tire marks, etc.).
• If perpendicular shots can't be taken, ideally, place visible squares with know dimensions. This will allow for perspective and distortion removal later.