zaterdag, februari 07, 2004
As more police departments abandon chemically processed film in favor of digital photography, the technology could be confounding for the justice system. Film images are subject to darkroom tricks, but because digital pictures are merely bits of data, manipulating them is much easier. And although willful evidence manipulation is rare, forensic specialists acknowledge that a poorly trained examiner incorrectly using computer enhancement programs can unwittingly introduce errors.
"What you can do in a darkroom is 2 percent of what Photoshop is capable of doing," said Larry Meyer, former head of photography for an insurance company. "There have been relatively few challenges to the use of digital technology as evidence and in most of them the courts have looked at them in a fairly superficial way," said Edwin Imwinkelried, an evidence expert at the University of California law school.
Concerns about the impeachability of digital photographs are one reason many police departments have been hesitant to ditch film for crime scene photographs and forensic analysis. In fact, some people who train law enforcement agencies in photography estimate that only 25 to 30 percent of U.S. police departments have gone digital — despite the cost benefits of no longer having to buy film and the ease with which digital pictures can be captured and disseminated. The police department in Santa Clara, Calif., bought 30 digital cameras recently but is holding off on giving them to detectives and technicians until the department specifies ways to lock away the original photos as evidence "so there can be no question that anything was changed," said Sharon Hoehn, an analyst for the department.
Law enforcement officials also worry about the limitations that still plague digital photography. Digital pictures can't be blown up as clearly for courtroom displays as well as film photos. Or the compression needed to store a digital file on disk can make the image blurry or blocky, potentially obscuring key details.
"Digital imaging for the most part has a long way to go to meet the quality of film," said Richard Vorder-Bruegge, an FBI forensic expert who chaired a panel that wrote guidelines for law enforcement use of digital imaging. For example, he said, a negative shot on traditional 200-speed film can produce the equivalent of 18 megapixels of resolution. Only highly specialized, expensive digital cameras approach that now; most that consumers buy are less than 5 megapixels. Vorder-Bruegge believes cops should stay with film for capturing close-up details of footprints and tire tracks.
Bron: AP.
"What you can do in a darkroom is 2 percent of what Photoshop is capable of doing," said Larry Meyer, former head of photography for an insurance company. "There have been relatively few challenges to the use of digital technology as evidence and in most of them the courts have looked at them in a fairly superficial way," said Edwin Imwinkelried, an evidence expert at the University of California law school.
Concerns about the impeachability of digital photographs are one reason many police departments have been hesitant to ditch film for crime scene photographs and forensic analysis. In fact, some people who train law enforcement agencies in photography estimate that only 25 to 30 percent of U.S. police departments have gone digital — despite the cost benefits of no longer having to buy film and the ease with which digital pictures can be captured and disseminated. The police department in Santa Clara, Calif., bought 30 digital cameras recently but is holding off on giving them to detectives and technicians until the department specifies ways to lock away the original photos as evidence "so there can be no question that anything was changed," said Sharon Hoehn, an analyst for the department.
Law enforcement officials also worry about the limitations that still plague digital photography. Digital pictures can't be blown up as clearly for courtroom displays as well as film photos. Or the compression needed to store a digital file on disk can make the image blurry or blocky, potentially obscuring key details.
"Digital imaging for the most part has a long way to go to meet the quality of film," said Richard Vorder-Bruegge, an FBI forensic expert who chaired a panel that wrote guidelines for law enforcement use of digital imaging. For example, he said, a negative shot on traditional 200-speed film can produce the equivalent of 18 megapixels of resolution. Only highly specialized, expensive digital cameras approach that now; most that consumers buy are less than 5 megapixels. Vorder-Bruegge believes cops should stay with film for capturing close-up details of footprints and tire tracks.
Bron: AP.
# posted by Jan-Edward : 23:42
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