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Research in action
Teeth as evidence
Could a dental database developed at Marquette
provide a new way to identify crime suspects?
By nicole sweeney etter
Investigators searched for answers in the brutal 1984 murder of an elderly Milwaukee woman. Their only clue: the bite wounds on her body. When the case came to trial, prosecuting attorney Daniel Blinka called Dr. L. Thomas Johnson to the stand. As a forensic odontologist, Johnson found similarities between the suspect’s teeth and
the victim’s wounds. His testimony helped put the man behind bars.
The case’s unusual particulars forced Blinka to chart new legal ground.
“Nobody in the state of Wisconsin had done a bite mark rape-murder case like this one before,” says Blinka, now a Marquette law professor. “And in fact, almost no case in the nation had ever been developed where the bite mark identification was the sole means of identification. So we were really reinventing the wheel.
 More than two decades later they are reinventing it again. With the help of other Marquette collaborators, Johnson is creating a database of 400 dental imprints that investigators could use as a statistical measuring stick. The database could provide a huge leap forward for the field of forensic odontology.
“This is important because in the cases where bite marks do surface, we’ll have the scientific mechanism to exploit any trace evidence that’s left behind,” Blinka says. “This is a powerful tool not only for pointing a finger at somebody but also for eliminating suspects.”
How it works
Bite mark evidence made its court debut as early as 1870, when it was used unsuccessfully to prosecute an Ohio man accused of killing his mistress. It later became critical during the trial of serial killer Ted Bundy, whose crooked teeth were imprinted in his victims’ flesh. But until now, no matter how distinctive the teeth, forensic odontologists could only say that it was “probable” that the bite marks were made by a particular suspect.
“If we prove what we’re setting out to prove with this pilot study, this could be expanded to thousands of samples,” explains Johnson, an adjunct professor of forensic dentistry in the School of Dentistry. “We could have a database that begins to approach that of mitochondrial DNA, which is a virtual identification.”
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| Daniel Blinka (left) and Dr. Tom Johnson |
Johnson’s team is collecting dental imprints from men ages 18-44, the demographic that most often commits crimes that include biting. Using computer software developed at Marquette, the researchers analyze the samples to precisely measure six identifying characteristics, including the width of the arch, width of the teeth, alignment and unusual characteristics such as missing or broken teeth. Then they statistically calculate how frequently these characteristics occur in the population.
So why is all this data important? Suppose a court asks, “How common is it for an adult male to have a lower jaw width of 2.28 centimeters or smaller and to have tooth
No. 24 turned at an inward rotation of 10 degrees or more?” Based on Johnson’s preliminary data, he could say that he was “highly confident” that less than 3 percent of adult males have that particular combination. As he accumulates more data, he expects to narrow the field even further.
Johnson’s other collaborators include Dr. Thomas Radmer, assistant professor of oral and maxillofacial surgery; Tom Wirtz, director of dental informatics; Peggy Van Scotter-Asbach, an adjunct assistant professor of dentistry; and two imaging specialists from the Wisconsin State Crime Laboratory. A handful of dental students play an important role measuring the dental imprints so that researchers can test the margin of error. The team follows rigorous standards of the Scientific Working Group on Imaging Technology, and the two-year pilot study is funded by the Midwest Forensic Resource Center in Ames, Iowa.
Evidence that’s hard to refute
For Van Scotter-Asbach, a former police officer, an interest in forensics is nothing new. She sees the database as a public service, a crucial tool that Marquette can give to the criminal justice system.
Bite wounds most often appear in cases of sexual assault, murder, child and elder abuse, Van Scotter-Asbach says. But the database could be used in other cases as well.
“Criminals are not the masterminds that TV makes them out to be,” she says. “They leave their dental imprints behind in a variety of ways. They bite into an apple, they bite into a Styrofoam cup, they leave a piece of chewing gum.”
She hopes that greater public awareness helps victims of assault. “Scratching your attacker to get DNA under your fingernails is not the only way to obtain evidence. You should also leave behind your dental pattern by biting your attacker,” she says.
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| The X and Y axes are reference points for measuring and analyizing the width of the teeth and dental arch and the angle of rotation of the incisors. Marquette’sSchool of Dentistry developed the software to measure dental characteristics. |
Johnson agrees that’s a smart tactic. “If you have this transfer of patterns between the two, it’s pretty hard to refute that the accused was not there, because the accused has a pattern on them that matches the victim, and the victim has a pattern on them that matches the accused,” he explains.
But the Marquette study won’t answer the question of why some people use their teeth as a weapon.
“What’s just as interesting to me is the psychology behind it,” Blinka says. “Biting is such a primitive form of aggression.”
Bite-mark evidence has come under fire in recent years because of a handful of highly publicized cases in which it was incorrectly used. In one case, the testimony of a forensic odontologist contributed to the wrongful conviction of an Arizona man whose name was later cleared through DNA.
“Unfortunately there have been cases where the quality of the evidence didn’t meet the strength of opinion, which is what we’re trying to counter here,” Johnson says. “We want to put some science into this, and it’s
something only dentistry can do.”
Filling a dental need
An opportunity other schools of dentistry don’t offer
 Jim Rogér couldn’t resist the pull of the School of Dentistry. He was studying dentistry at Temple University when he heard about Marquette’s research-intensive option. He packed his bags for Milwaukee and started class the next week.
“I wouldn’t have done that for just any place,” he says. Rogér was attracted to the dual D.D.S./Ph.D. program that Marquette offers in conjunction with the University of Rochester. He hopes the specialized research training and Ph.D. will pave the way to a career in academia.
“Marquette is really on the map as a research-focused program,” says Rogér, who this summer will conduct pathology research on Sjögren’s syndrome, an autoimmune disorder that can cause dry mouth and eyes.
Until 1999, the dental school didn’t have a formal student research program. “Now we have the most-comprehensive and talked about student research program of all dental schools nationwide,” says Dr. Anthony Iacopino, professor of general dental sciences and faculty adviser to the student research group.
It helps that Marquette has one of the largest chapters of the National Student Research Group, which is part of the American Association of Dental Research. For both 2005 and 2006, the local chapter won three national awards, including for most new members. Rogér is president of the national group, the first Marquette student to hold the post.
So what’s the Marquette difference? With the help of the National Institute of Dental Research, Marquette became the first dental school in the country to create a dedicated research and scholarly track in its curriculum. Students can take up to three months a year for research and still graduate on time.
The dental school’s motivation was simple. Thanks to the more lucrative lure of private practice, there’s a huge shortage of dental teachers and researchers.
“All dental schools are trying desperately to get students interested in these careers and without much success,” Iacopino explains. “We decided the niche that we could fill was that we could be really innovative in getting students interested in teaching and academic careers through the normal course of the dental curriculum.”
Student research topics range from new biomaterials and techniques for restoring teeth to gerontology to forensic odontology. Students can do their research anywhere in the country, and grants cover all of their travel and research expenses.
The partnership with the University of Rochester is unusual. While Rochester does not have a dental school, it is home to the top dental research in the country, Iacopino says.
“Students get to couple their excellent clinical training at Marquette with top research training at Rochester,” he says.
The focus on student research has also inspired more faculty participation. Since 1999, the dental school has increased its faculty mentorship by 50 percent, increased faculty publications and grants by 60 percent, and more than tripled the money that it spends on research.
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