Friday, October 27, 2017

Dodging Daubert to Admit Bite Mark Evidence

At a symposium for the Advisory Committee on the Federal Rules of Evidence, Chris Fabricant juxtaposed two judicial opinions about bite-mark identification. To begin with, in Coronado v. State, 384 S.W.3d 919 (Tex. App. 2012), the Texas Court of Appeals deemed bite mark comparisons to be a “soft science” because it is “based primarily on experience or training.” It then applied a less rigorous standard of admissibility than that for a “hard science.”

The state’s expert dentist, Robert Williams, “acknowledged that there is a lack of scientific studies testing the reliability of bite marks on human skin, likely due to the fact that few people are willing to submit to such a study. However, he did point out there was one study on skin analysis conducted by Dr. Gerald Reynolds using pig skin, ‘the next best thing to human skin.’” The court did not state what the pig skin study showed, but it must have been apparent to the court that direct studies of the ability of dentists to distinguish among potential sources of bite marks were all but nonexistent.

That dentists have a way to exclude and include suspects as possible biters with rates of accuracy that are known or well estimated is not apparent. Yet, the Texas appellate court upheld the admission of the "soft science" testimony without discussing whether it was presented as hard science, as "soft science," or as nonscientific expert testimony.

A trial court in Hillsborough County, Florida, went a step further. Judge Kimberly K. Fernandez wrote that
During the evidentiary hearing, the testimony revealed that there are limited studies regarding the accuracy or error rate of bite mark identification, 3/ and there are no statistical databases regarding uniqueness or frequency in dentition. Despite these factors, the Court finds that this is a comparison-based science and that the lack of such studies or databases is not an accurate indicator of its reliability. See Coronado v. State, 384 S.W. 3d 919 (Tex. App. 2012) ("[B]ecause bite mark analysis is based partly on experience and training, the hard science methods of validation such as assessing the potential rate of error, are not always appropriate for testing its reliability.")
The footnote added that "One study in 1989 reflected that there was a 63% error rate.” This is a remarkable addition. Assuming "the error rate" is a false-positive rate for a task comparable to the one in the case, it is at least relevant to the validity of bite-mark evidence. In Coronado, the Texas court found the absence of validation research not preclusive of admissibility.  That was questionable enough. But in O'Connell, the court found that the presence of research that contradicted any claim of validity “inappropriate” to consider! That turns Daubert on its head.

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