Death unmasked


By Barry Fox THE computer system used to reconstruct the face of Ötzi, the 5000-year-old iceman, has been harnessed to help solve a horrific murder in Germany. One of the inventors of the system, Peter Vanezis of the Department of Forensic Medicine and Science at the University of Glasgow, has been asked to help police re-create a young murder victim’s face from her skull. Forensic scientists have for many years sculpted face models from clay—as recounted in the thriller Gorky Park—to help identify decomposed or mutilated corpses. But the technique is slow, requires artistic skill and can be biased by the subjective judgment of the sculptor. Various computer techniques have been developed to overcome these limitations. In the technique used by Vanezis, which he recently demonstrated to a meeting of forensic experts in Glasgow, the skull is mounted on a platform and rotated slowly through a laser beam. The laser scans the moving skull in lines and the information is fed to a computer. It takes just 30 seconds to capture 20 000 surface coordinates, with a resolution of 0.5 millimetres. The computer uses triangulation to convert the coordinates into a 3D model, which can be moved about and viewed from any angle. The operator then uses a mouse to drag and drop skin textures and key facial features onto the template, from a library of pre-programmed options. The choice of skin colour and features such as lip and nose shape is guided by whatever information on race, colour and sex is available. The software moulds the skin over the skull model like a mask, so that it mimics the effect of a real skull under real skin. Vanezis has tried the system on Ötzi, the frozen corpse found in 1991 in a glacier on the border between Italy and Austria. The 3D image gives a feel for what Ötzi looked like before his death 5000 years ago. Vanezis is now helping the German police solve a murder with a strange twist. They found the body of a young woman, believed to be a Turkish guest worker or immigrant, who had been raped and strangled, then burnt to try to conceal her identity. DNA tests revealed that she had been raped by her father. But knowing the father was involved isn’t enough:
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