Monday, October 14, 2013

Bite me: Validating research supporting forensic dentistry inhibited by lack of willing bite-mark victims

I ran across an interesting article documenting critiques of forensic dentistry. In it, bite mark expert Dr. Gregory Golden:
concedes that there’s little scientific research to back claims from forensic odontologists in court — but he hopes to see that change. "What we’re trying to do," he says, "is to develop proper, unbiased research techniques that take into consideration real-time mechanisms or setups for researching bite marks."

The problem, he says, is that it’s difficult to conduct realistic studies on how bite marks injure living human flesh. In the past, studies have been conducted on cadavers and anesthetized pigs, with dental models mounted in vice grips. But such studies don’t accurately reflect bites on living human flesh, and Golden adds that "it’s almost impossible to find voluntary subjects offering themselves to be bitten severely enough to be wounded."
In the meantime, though, he wants to keep drawing  his expert witness fees until the science either justifies or debunks his premises. While it's understandable that few subjects would be willing to be seriously bitten in service to science, that's not a good excuse for courts to admit unreliable evidence.

To me, though, the question posed in the headline - whether forensic dentistry should be "banned" - frames the issue too starkly. The real question is, "under what circumstances is its use appropriate?". Is there a role in the justice system for forensic odontology? Sure. As the article mentions, it has been useful in identifying victims in mass casualties, matching teeth to dental records. And it can play an important role in excluding suspects. But there's little basis for relying on such testimony to accuse someone -  certainly not as the primary evidence against them, as was done in the New York case resulting in a recent DNA exoneration that inspired the article.

Unfortunately, as the National Academy of Sciences articulated in a 2009 report, many forensic disciplines aren't really "science" at all and forensic odontology is one of them. Instead, like tool mark or hair-and-fiber analyses, the method of identification involves subjective comparison, not scientific proof. The justice system has so firmly incorporated these non-scientific disciplines into the marrow of its being that it would be unrealistic to argue all comparative disciplines should be abandoned - e.g., it's been shown that cognitive bias can produce errors in fingerprint comparisons but the likelihood that evidence will ever be excluded from court is virtually nil. But some disciplines are more reliable than others and forensic dentistry is definitely one of the shakier, less credible examples.


Anonymous said...

I have two questions:

If bite marks are present, shouldn't DNA from saliva be present also?

If the saliva has been destroyed so that no DNA is recoverable, won't the bite marks have deteriorated to the point they are useless?

If the answers are yes, then bite mark evidence is not needed. If the answers are no, then I questions the science.

Anonymous said...

If the bite analysis indicates that the bite was left by someone missing a tooth, and suspect is not missing that tooth, should the court allow the evidence to be presented?

Gritsforbreakfast said...

@2:56, today that's generally true, but bite mark evidence was used for years before DNA came into prominence so there are lots of cases out there with no DNA testing.

As for missing a tooth, etc., I agree that evidence could be used to exclude suspects (and the post acknowledged that). But since lots of folks are missing teeth, that evidence would be inconclusive as a positive indicator of guilt, IMO.

Anonymous said...

Any attempt to identify the culprit must be resisted and those methods discredited.

Gritsforbreakfast said...

5:09, your schtick is as tired as it is lame. Nothing "must be" discredited, it's just that this evidence has been. Send your complaints to the National Academies of Science, they're the ones that brought the issue to the fore.