The realm of gleaning forensic science fact from fiction is an ongoing chapter in the larger subject of scientific progress. Empirical testing and re-testing are the cornerstone of how science evolves. But, what about practices that have had no legitimate testing at all?
Welcome to the world of bitemark identification. The Texas Forensic Science Commission recommended banning it from courts.
Here’s a description of common testimony in homicide trials when the prosecution and defense hire their own experts to review and postulate testimony on the origins of skin injury patterns on victims of violent crime.
Note: this is an actual case that has NOT resulted in an exoneration.
“Dr. John Kenney and Dr. Lowell Thomas Johnson testified as experts for the State that certain marks on the victim’s body were bite marks inflicted by defendant. However, Dr. Larry Pierce and Dr. E. Stephen Smith testified as experts for the defense that the marks were not bite marks and that they were not inflicted by defendant. It is clear that all of these witnesses were qualified to testify as bite mark experts.”
The jury deliberated on the effects of such diverse testimony. All these experts were vetted by the trial judge as being members of the appropriate “scientific community” and as such, were allowed to use their favorite methods. If you are wondering what “favorite” entails. At the time of this trial, there were no published guidelines determined by the American Board of Forensic Odontology. Bitemark guidelines and standards were not formulated until 1995. This later evolution did not reject “identification of one human being” from a scant collection of bruises and abrasions. Bitemark identification of a singular person was taken off the books in a 2013 rewrite. Lesser conclusions are still allowed by this small AAFS group although they can’t scientifically prove that their methods are valid and reliable (reproducible between multiple examiners).
Other cases of the quoted prosecution experts that HAVE resulted in full exonerations are:
This saga will continue….
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Over a hundred years ago, Judge Learned Hand summed up the problem with competing experts as follows:
How can the jury judge between two statements each founded upon an expertise confessedly
foreign in kind to their own? It is just because the [jurors] are incompetent for such a task that
the expert is necessary at all.
According to Hand, testimony from competing experts is not helpful to the jury:
One thing is certain, they will do no better with the so-called testimony of experts than without,
except where it is unanimous. If the jury must decide between such, they are as badly off
as if they had none to help.