Fifteen years ago, Roy Brown, a hard-drinking man with a criminal record, was convicted of stabbing, beating, biting and strangling a social worker in upstate New York. The case rested largely on one piece of forensic evidence: bite marks on the victim’s body that the prosecution’s witness, a local dentist, said matched Mr. Brown’s teeth.
On Tuesday, Mr. Brown was released from prison, after DNA testing on the saliva left by the biter proved his innocence and implicated someone else in the crime. At the time of his conviction, Mr. Brown, 46, was missing two front teeth. The bite marks, meanwhile, had six tooth imprints.
The prosecution’s expert testified that Mr. Brown could have twisted the victim’s skin to fill the gaps his missing teeth would have left on the bite mark. Despite rebuttal from the defense, whose expert said the bite marks excluded Mr. Brown, it took jurors five hours to return a guilty verdict.
What happened to Mr. Brown is hardly an aberration. Prosecutors have invoked bite-mark matches to secure convictions in numerous cases, only to see these convictions overturned when DNA or other evidence has become available.
In spite of the evolution of other forensic sciences, bite-mark analysis remains an inexact tool. A 1999 study by a member of the American Board of Forensic Odontology, a professional trade organization, found a 63 percent rate of false identifications.
Why is it, then, that bite-mark analysis remains part of the forensic arsenal? There is, experts say, a mix of ignorance on the part of jurors and defense lawyers about the evidence’s scientific shortcomings and the overzealousness of prosecutors and their expert witnesses, who are seen as too quick to validate an unproven technique.
As the pace of overturned convictions increases, however, the courts are growing more skeptical of the absolute conclusions drawn by bite-mark experts and, in turn, are becoming more receptive when defense lawyers rebut the analysis.
Lawyers, for their part, are taking steps to counter what they call the “C.S.I. effect,” when juries become overly impressed by forensic evidence. During jury selection, it is not uncommon for them to ask potential jurors about their television-watching preferences to weed out those who seem unable to separate fact from fiction.
The key, experts say, is for lawyers to know enough about the subjective components of bite-mark analysis to refute it effectively in court.
“If you say that this bite fits this person and nobody else in the world, and if you use the bite mark as the only piece of physical evidence linking an attacker to his victim, that’s not science — that’s junk,” said Dr. Richard Souviron, chief forensic odontologist at the Miami-Dade Medical Examiner’s Office.
As people age, Dr. Souviron said, their jaws expand, changing the position of their teeth. Teeth can be chipped, broken or just pulled out; skin shifts when it is bitten. And, one must ask, was the victim moving? If the bite was on the chest, was the arm stretched above the head or resting next to the torso?
“There are just too many variables,” said Dr. C. Michael Bowers, author of “Forensics Dental Evidence: An Investigator’s Handbook,” published in 2004.
And there is also what David L. Faigman, a professor at the University of California Hastings College of the Law, calls the “context effect.” Because most forensic scientists learn a lot about the suspect before analyzing the bite mark, “it’s easy for them to see what they are expected to see,” Mr. Faigman said.
Experts, he added, “can basically be prepped to see a match.”
Bite marks, however, can be helpful in excluding someone as a suspect, or determining that the suspect could be the one who inflicted the bite, many experts and defense lawyers agree.
“If you limit bite-mark analysis to its accepted validity, it’s not inappropriate for an expert to say that a certain suspect is not the biter,” said Christopher Plourd, a lawyer in San Diego who has represented several suspects whose trials revolved around bite-mark evidence. “But that’s as far as you should go.”
In 1995, forensic odontologists moved to avoid using the term “match” in their analysis, so as to avoid giving the impression that the bite mark belongs to a specific suspect and no one else. But similar, if nuanced, phrases still find their way into court, causing confusion. The courts, however, do not have guidelines restricting the use or presentation of bite-mark analysis.
“I feel very strongly that if the courts were a little bit more vigilant or perhaps simply a little bit more informed that they would come very close to excluding a lot of this evidence,” Mr. Faigman said. “Or, at the very least, they would tell that the evidence could come in, but for very modest purposes.”
1 comment:
3. It was interesting how a local dentist was able to match Mr. Brown's teeth with the bitemarks. I did not expect that from a local dentist.
2. It was good how gabby mentioned the 1999 study of false identifications. It adds detial how she tells us that there was a 63% rate of false identifactions.
1. Also, Gabby adds detail how she says in 1995 Forensic scientists abandoned the term Matched because it doesnt deifnetly mean it belongs to a specific person. Now they say similar.
2. I think this article could have been better if gabby had expanded more on the details of the crime.
1. The article could be organized better in paragraphs.
1. I enjoyed reading this article because it was very well presented and I found this case concerning bite-marks to be very interesting.
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