The Empire Page Editorial
Beware the Pitfalls of Digital Evidence
by Scott Christianson
ALBANY -- The use of doctored photographs in political campaigns isn’t the only danger posed by today’s imaging technology.
In the last several years, the rapid proliferation of digital technology has revolutionized law enforcement, equipping police with digital video units to conduct surveillance and capture crimes in progress, digital cameras to photograph crime scenes, computer systems to store and retrieve data, software to create and edit images, and scanners and printers to transfer fingerprints and other data. Prison guards and airport security officers wave scanners to detect minute traces of explosives or drugs. The list keeps growing.
Digital gadgetry has proven so popular because of the tremendous speed and ease with which it can used to carry out multiple tasks. It also has enabled police to do things that previously weren’t possible, such as enhance a distorted fingerprint found at a crime scene in order to match it to an individual’s print in the police database.
As a result, digital imaging has become an integral tool of law enforcement one which daily contributes to countless arrests and convictions all over America. Police and prosecutors utilize some form of it thousands of times per day.
But digital imaging’s rampant growth in forensic science to provide evidence of crime poses some hidden dangers.
Digital technology relies on Charged Coupled Devices (CCD’s) that represent color by averaging the colors near a given light receptor. As a result, CCD’s degrade detail and make the color less accurate than ordinary (analog) film. Commonly available software also allows the police and other users to manipulate digital images to enhance their quality and make them more identifiable or distinct.
Some of this technology was developed for the space program, intended for specific scientific uses. Adapted to the exacting world of forensics, however, where potential evidence is scrutinized, digital technology poses built-in errors and potential for abuse.
Distortion of crucial minutiae in a fingerprint, for example, can alter an image’s appearance to assume another identity, matching it to the wrong person. Remote access software can enable a technician or hackers to secretly manipulate details. And transferring an image through multiple digital systems can combine to produce even more changes.
When used by persons who have been inadequately trained in its use and who are not carefully supervised, the new technology can do considerable damage.
Computer glitches or human errors can result in false positives that contribute to needless delays, waste of investigative resources, and other problems.
One danger is that such inaccurate images can serve as convincing scientific proof to erroneously clear or convict criminal suspects, without anyone ever knowing the difference. This already may have occurred in some cases, particularly where the original images involved hard-to-read fingerprints, footprints, bite marks, tire patterns, or ballistics comparisons. Nobody knows the extent of its mistakes.
Edward Imwinkelried, a law professor at the University of California at Davis, one of the nation’s leading experts on criminal evidence, noted that thus far the courts have generally accepted digital evidence. But that could change.
Legal scholars observe that the "best evidence doctrine" requires that, to be produced as evidence, a "writing" must ordinarily be the original, and writing is broadly interpreted to include photographs. Any duplicate must accurately reflect the raw evidence. Yet digital enhancement adds or subtracts pixels so that it, by its nature, changes the image.
In 1997 the FBI formed the Technical Working Group on Imaging Technologies to gather and disseminate accurate information regarding the proper application of digital and other imaging technologies throughout the criminal justice system. Now identified as SWGIT, the group has issued some general guidelines and recommendations for the use of various imaging technologies. Its guidance, however, hasn’t regulated the flood of digital technology sweeping law enforcement, and uniform standards still haven’t been implemented.
Michael Cherry, an imaging specialist who in the late 1980’s helped to pioneer the replacement of film photography with electronic photography, said he is deeply concerned about the application of digital technology in forensic science. He is developing Validation Solutions, Inc. as a laboratory to review digital evidence and advise law enforcement officials and defense lawyers if it should be challenged.
Prof. Imwinkelried agreed with Mr. Cherry, saying, "The fact that the technology was validated for the space program doesn’t mean it can be used in forensics. Another body of research is needed."
Thousands of alleged lawbreakers now find themselves cleared or targeted, based on the assumption that "pictures don’t lie." But justice in the digital age increasingly relies on imagery of undetermined provenance, accuracy and susceptibility to abuse.
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Scott Christianson, a former New York state criminal justice official, is the author of "Innocent: Inside Wrongful Conviction Cases" (2004) and other books.
