It has sent innocent men to death row, given defense attorneys fits and splintered the scientific community.
For a decade now, attorneys and even some forensic experts have ridiculed the use of bite marks to identify criminals as sham science and glorified guesswork.
Now researchers at Marquette University say they have developed a first-of-its kind computer program that can measure bite characteristics. They say their work could lead to a database of bite characteristics that could narrow down suspects and lend more scientific weight to bite-mark testimony.
"The naysayers are saying, 'You can throw all this out. It's junk science. It's voodoo. This is a bunch of boobs that are causing a lot of problems and heartaches for people,'" said team leader Dr. L. Thomas Johnson, a forensic dentist who helped identify victims of the cannibalistic Milwaukee serial killer Jeffrey Dahmer. "It's a valid science if it's done properly."
Teeth are unique
Skeptics already are taking shots.
"Scientifically illiterate," Dr. Mike Bowers, a deputy medical examiner in Ventura County, Calif., and a member of the American Board of Forensic Odontology, said of Johnson's work.
Built around the assumption that every person's teeth are unique, forensic dentistry has used bite impressions to identify criminals for 40 years. Bite marks on a young woman helped convict serial killer Ted Bundy of murdering her and another college student.
But critics say human skin changes and distorts imprints until they are nearly unrecognizable. As a result, courtroom experts end up offering competing opinions.
"If the discipline lends itself to opposing experts, it's not science," said Peter Neufeld, co-director of the Innocence Project, which works to free wrongfully convicted inmates.
Since 2000, at least seven people in five states who were convicted largely on bite-mark identification have been exonerated, according to the Innocence Project.
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.
Grants won for bite research
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.
Dr. 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.
Dr. 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."