ScienceDaily (Sep. 17, 2009) —
Against the backdrop of last week's Congressional hearing into the
future of forensic science, researchers from the University at
Buffalo's Laboratory for Forensic Odontology Research in the School of
Dental Medicine, have published a landmark paper on the controversial
topic of bitemark analysis.
The Congressional hearing focused on the findings of a National
Academy of Sciences (NAS) report on the scientific basis of forensic
disciplines. Among the pattern evidence fields (fingerprints, tool
marks, etc.) that were reviewed in the NAS report, bitemark analysis
received critical commentary. During the hearing, Innocence Project
co-founder Peter Neufeld introduced Roy Brown, wrongfully convicted on
bitemark evidence and later exonerated through DNA analysis.
In anticipation of the NAS report, the new UB study published in the
Journal of Forensic Sciences challenges the commonly held belief that
every bitemark can be perpetrator identified.
"Bitemark identification is not as reliable as DNA identification,"
explains the study's lead author Raymond G. Miller, D.D.S., UB clinical
associate professor of oral diagnostic sciences.
"With DNA, the probability of an individual not matching another can
be calculated," he says. "In bitemark analysis, there have been few
studies that looked at how many people's teeth could have made the
bite."
Miller's co-authors include UB's Peter J. Bush; Robert Dorion,
D.D.S., DABFO, UB adjunct professor of oral diagnostic sciences; and
Mary A. Bush, D.D.S., UB assistant professor of restorative dentistry.
Dorion is the editor of the only comprehensive textbook on the subject
of bitemarks in forensic science, Bitemark Evidence: A Color Atlas and
Text, and is currently the odontology section representative to the
board of directors of the American Academy of Forensic Sciences.
The current study investigated three main questions: is it possible
to determine biter identity among people with similarly aligned teeth;
is it possible to determine how many individuals from a larger sample
might also be considered as the biter; and, if there is bite pattern
distortion, is it enough to rule out a specific biter while still
including a non-biter?
To answer these questions, the researchers gathered 100 stone dental
models (replicas of the dentition), which were measured and divided
into 10 groups based upon the misalignment patterns of the teeth. After
randomly selecting one model from each of the 10 groups, the
researchers impressed bitemarks on cadaver skin. After the bitemarks
were created, they were then photographed and the indentations were
compared to the dentitions using overlays created with photographic
software.
The authors are one of the first to use a human skin model rather
than animal models or non-elastic biting substrate, such as wax or
Styrofoam. Current human subject restrictions limit experimentation on
living subjects.
"Living bitten tissue may bleed or bruise," explains Miller. "The
initial bitemark indentations rebound shortly after infliction often
leaving a diffuse bruising that may be difficult to measure accurately.
The indentations produced in our study represented the best conditions
for measurement."
The results indicated that when dental alignments were similar, it
was difficult to distinguish which set of teeth made the bites.
Distortion noted in the bitemarks allowed matches even from different
alignment groups. Therefore, the researchers concluded that bitemarks
should be very carefully evaluated in criminal investigations where
perpetrator identity is the focus of a case.
As Miller notes, "In the past 10 years, the number of court cases
involving bitemark evidence that have been overturned led us to
question the reasons for the erroneous bitemark identification. It's
important to recognize the serious consequences of a misidentification
for the accused, the victim, the families involved, the justice system
and the possibility that the perpetrator is still at large."