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In Arizona, Ray Krone was found guilty in 1992 of killing a Phoenix bartender based largely on expert testimony that his teeth matched bites on the victim. He was sentenced to death, won a new trial on procedural grounds, was convicted again and got life. But DNA testing in 2002 proved he wasn't the killer. Krone was freed and won a spot on the ABC reality show "Extreme Makeover" to remake his teeth. In Mississippi, forensic odontologist Dr. Michael West has come under fire after he testified in two child rape-murders in the 1990s that bite marks positively identified each killer. Kennedy Brewer was sentenced to death in one case, and Levon Brooks got life in prison in the other. DNA tests later connected a third man to one of the rapes, and investigators say he confessed to both murders. In Brewer's case, a panel of experts concluded that the bites on the victim probably came from insects. Brewer and Brooks were exonerated earlier this year. Determined to prove that bite analysis can be done scientifically, Johnson and his team won about $110,000 in grants from the Midwest Forensic Resources Center at Iowa State University and collected 419 bite impressions from Wisconsin soldier volunteers. They built a computer program to catalog characteristics, including tooth widths, missing teeth and spaces between teeth. The program then calculated how frequently -- or infrequently -- each characteristic appeared. He hopes to collect more impressions from dental schools across the country to expand the database into something close to law enforcement's DNA databanks. With enough samples, the software could help forensic dentists answer questions in court about how rarely a dental characteristic appears in the American population. That would help exclude or include defendants as perpetrators, Johnson said. He acknowledged that his software will probably never turn bite-mark analysis into a surefire identifier like DNA and that he would need tens of thousands of samples before his work would stand up in court. But "this is the first step toward actually providing science for this type of pattern analysis," Johnson said. Bowers, who often testifies for the defense in criminal cases, said Johnson should instead study how skin changes can distort bite marks. David Sweet, a forensic dentist at the University of British Columbia, said he has been working on a database similar to Johnson's for the past decade. He said he has offered Johnson casts and reproductions of the hundreds of bite impressions he is making. Robert Barsley, a Louisiana State University dental professor and vice president of the American Academy of Forensic Science, said he, too, would send Johnson hundreds of bite impressions. "His work could certainly be a benefit," Barsley said. "I don't think it will solve the problem, but it would be a step in the right direction." Related Links: |
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