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An attacker bites his victim. A criminal munches on a sandwich before fleeing the scene. And those pearly whites might leave just the clue needed to capture the perpetrator.
Daniel Blinka , J.D., Ph.D. (left),
Law Professor, and L. Thomas Johnson, D.D.S.,
Forensic Odontologist and Adjunct Professor of Dentistry. Together, they're creating a database that could advance the field of forensic odontology.
The value of bite mark evidence became obvious 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.
L. Thomas Johnson, D.D.S., is working to change that. Johnson has assembled an interdisciplinary team, including Marquette law professor Daniel Blinka, J.D., Ph.D., to create a database of dental imprints that investigators could use as a statistical measuring stick.
“Dentistry has always assumed that everybody’s teeth are unique. But the problem is, there’s no way that scientifically you can justify that,” says Johnson, an adjunct professor of dentistry who has worked as a forensic odontologist for more than 40 years.
“If we prove what we’re setting out to prove with this pilot study, this database could be expanded to thousands of samples. We could have a database that begins to approach that of mitochondrial DNA, which is a virtual identification.”
Johnson’s team is collecting 400 dental imprints from men ages 18-44, the demographic that most often commits crimes that involve biting. Using 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 those characteristics would occur in the population.
So why is all that 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 would have that particular combination. As he accumulates more data, he expects to narrow the field even further.
The team is following the rigorous standards of the Scientific Working Group on Imaging Technology, and Johnson has several people measuring the dental imprints so that he can test the margin of error. The two-year pilot study is funded by the Midwest Forensic Resource Center in Ames, Iowa. Johnson’s team is also working with the Wisconsin State Crime Laboratory.
Many people assume that DNA is the end all, be all of criminal investigations, but that’s not always true, Blinka says. During his time in the Milwaukee County District Attorney’s Office, Blinka worked on a handful of bite mark cases, including a nationally prominent case in which bite marks were the sole evidence found at the crime scene.
“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.”
But 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.”
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| Identity: | Catholic, Jesuit, private |
| Established: | 1881 |
| Location: | Milwaukee, Wisconsin |
| Undergraduate: | 8,048 |
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