THERE’S GOOD NEWS AND BAD NEWS: LOWER PROCESSING COSTS AND DIMINISHING FILM AVAILABILITY HAVE DRIVEN FORENSIC SCIENCE TOWARD DIGITAL PHOTOGRAPHY.

Last summer, Reuters admitted that two digital photographs presented as part of its coverage of the 2006 Israel-Lebanon conflict had been significantly altered before being published. One photo showed two heavy columns of black smoke billowing from Beirut buildings after an Israeli air attack. Anothershowed an Israeli aircraft supposedly firing several missiles.

The images were withdrawn after manipulation was exposed by a U.S. blogger (LittleGreenFootballs.com), who accused Reuters of distorting the first photograph to include more smoke and damage than actually existed. In the other, an Israeli Air Force F16 that had deployed a single flare was digitally doctored to make it appear that several missiles had been fired. Reuters subsequently admittedt hat the photographer had altered the images using photo-editing software.

The incident illustrates the principle issue with the use of digital photography in forensics, especially in fields like news gathering and criminal justice where the pressures of ethics and public trust are pervasive and presumably paramount.

“Manipulation of digital photographs is not only quite possible, but quite easy,” said Howard Adelman, M.D., a New York forensic pathologist. “With digital photography, I always try to imprint the date and time on the photoand, especially with specimens and bodies, have a ruler in the picture.”

Alteration of digital photographs is far simpler than traditional film. Almost anyone with just a little practice with basic imaging software can produce changes that are nearly impossible to detect without special steps. A person can remove a blemish or a scar from a portrait, a scratch or dent on a car in a newspaper add, or change a license plate, the time on a clock, or background objects in a crime scene photo.

PICTURE OF STEALTH
The potential for image manipulation provides a basis for broad admissibility challenges in court. The judiciary has had to increase its scrutiny to be assured digital evidence is authentic and has not been altered or ‘Photo-shopped.’ There have always been legal issues associated with the introduction of photographic evidence, but the digitalization of photographs presents new challenges toforensic scientists to track and maintain image integrity.

“The ease with which images can be manipulated heightens the need for proper authentication,” said Florida attorney Catherine M. Guthrie, a staff researcher at the National Clearinghouse for Science, Technology, and the Law at Stetson UniversityCollege of Law. Guthrie is co-author of an upcoming law review article titled “The Authentication of Digital Images: The Swinton Six.”

Authentication essentially means that evidence, in this case digital images,are in fact what they purport to be. In other words, the pictures and the processes used to generate them are accurate and reliable, Guthrie said.

Los Angeles attorney Darren Enenstein said one way to authenticate digital images is by using hash functions, or algorithms that give a mathematical formula (or hash value) to each image.

“You can then compare the photo’s hash value if it is moved or copied. If the hash value matches then it is the exact same image, with no changes,” Enenstein said. Enenstein cautioned that algorithms used to compress images for storage can change a hash value.

Software packages, such as Adobe Photoshop CS, are available that produce change reports for digital photo files. Camera manufacturers are also sensitive to the image integrity issue. Several years ago Olympus released its Image Authentication System that can be used to verify if an image has been altered. Canon currently has a Data Verification Kit for its EOS 1Ds and EOS-1D mark II cameras that can detect changes as small as one bit.