Opinion writer


About a year ago, I published a four-part series on the use of bite mark evidence in criminal cases. To summarize, the series pointed out that there has never been any scientific research to support the notion that human bites are individually unique, and that even if this was true, there’s also no research to support the notion that human skin is capable preserving bite marks in a useful way. What little scientific research that has been done in fact undermines both assumptions. Nevertheless, the courts have been allowing bite mark evidence for four decades, and to date, not a single court in the country has ruled in favor of a challenge to its admissibility.

Since then, an internal study by the American Board of Forensic Odontology (a group for bite mark analysts) further cast doubt on the legitimacy of the discipline, finding widespread disagreement even among the most experienced analysts over basic questions like what is and isn’t a bite mark. Moreover, the Texas Forensic Science Commission is now casting a skeptical eye on the validity of bite mark analysis, and a senior science advisor to President Obama has called for its eradication from the courtroom. There have also been a couple federal court cases in which judges have essentially declared the entire discipline to be a fraud, though both came in ruling that were only tangentially related to the legitimacy of bite mark analysis.

But the most recent news concerns the New York trial of Clarence Dean. In 2013, attorneys for Dean asked for a hearing on the scientific admissibility of the bite mark evidence that prosecutors wanted to introduce at his trial. Judge Maxwell Wiley granted them the hearing. This was significant because it was the first such hearing ever conducted, even though bite mark evidence has been used in criminal cases since the 1970s. Previous courts had upheld its validity by denying challenges to its validity made during appeals and in post-conviction petitions.The hearing also came just as the aforementioned scientific research was beginning to unravel the core principles of bite mark analysis.

In parts three and four of my series, I noted that the Manhattan prosecutor in that case, Assistant District Attorney Melissa Mourges, was not advocating for admitting bite mark evidence in the Dean case, she had become an evangelist for bite mark analysis in general. That evangelism included speaking at conferences and symposiums, and launching pointed, often very personal attacks at skeptics, including longtime bite mark critic Michael Bowers, and Mary and Peter Bush, the scientists whose research had begun to expose the field as fraudulent.

Mourges’s brief for the hearing in the Dean case was rife with misleading claims and in some places, outright deception. Here’s one example, from my series, discussing how Mourges handles a 2009 National Academy of Sciences report that criticized bite mark analysis in pretty harsh terms:

In another portion of the brief, Mourges selectively quotes part of the the report, cutting out some critical language. She writes:

When Dr. Kafadar and her NAS committee created the NAS report, they wrote a summary assessment of forensic odontology. In it they said that “the majority of forensic odontologists are satisfied that bite marks can demonstrate sufficient detail or positive identification …

That ellipsis is important, as is the word that comes before the quote. Here’s the passage quoted in full:

Although the majority of forensic odontologists are satisfied that bite marks can demonstrate sufficient detail for positive identification, no scientific studies support this assessment, and no large population studies have been conducted. In numerous instances, experts diverge widely in their evaluations of the same bite mark evidence, which has led to questioning of the value and scientific objectivity of such evidence.

Bite mark testimony has been criticized basically on the same grounds as testimony by questioned document examiners and microscopic hair examiners. The committee received no evidence of an existing scientific basis for identifying an individual to the exclusion of all others.

The report only acknowledges the near consensus within the community of bite mark analysts for the purpose of criticizing them. Mourges’s selective quotation implies that the report says the relevant scientific community accepts bite mark matching. The full passage reveals that the report is essentially pointing out just the opposite: The insular community of bite mark analysts may believe in what they do, but the larger scientific community is far more skeptical.

In other words, Mourges attempted to attribute to the report the precise opposite of what it claimed. That’s about the level of discourse that pervades the entire document. And yet Mourges won. In September 2013 Judge Wiley ruled that the evidence was admissible, although he never published an opinion to explain his decision.

As noted, since that decision there have been some major new developments, all of which cast further doubt on the validity of bite mark analysis. In light of those developments, Clarence Dean’s attorneys asked Wiley for another hearing. Last week, the Manhattan DA’s office sent Wiley a remarkable memo, informing him that they would be withdrawing the evidence. That’s good news for Clarence Dean. But it also means we’ll have to wait for another day before the first court in America declares bite mark evidence inadmissible (not that there’s any guarantee Wiley would have done so).

The memo itself is an incredible read. It wasn’t written by Mourges herself — it was written by Deputy Bureau Chief Robert Ferrari — but it’s an amusingly angry and blustery defense of both Mourges and bite mark analysis. It actually begins by accusing Mourges’s critics of sexism, claiming Dean’s attorneys made “ad feminam attacks on an Assistant District Attorney.” It isn’t clear which criticisms of Mourges the Manhattan DA’s office finds sexist. But as I noted in my series, according to several people in attendance, it was actually Mourges who made crude comments about Mary Bush’s physical appearance during a presentation at a 2014 ABFO event in Seattle.

The memo goes on to bite mark analysis for three pages before finally informing Wiley that the state will be withdrawing the bite mark evidence in Dean’s case. Ferrari’s explanation for this decision is that the bite mark evidence has “relatively slight probative value” in the Dean case, which makes one wonder why they fought so hard to introduce it in the first place.

Most of the arguments Ferrari makes in defense of bite mark evidence are similar to those Mourges made in her original brief that I examined in my series, so I won’t go into them here. (Fun aside: The memo also twice attacks the credibility of my reporting by referring to me as a mere “blogger.” Horrors!)

But in the few places where he addresses the new developments, he’s just as slippery as Mourges. Referring to the internal ABFO study referenced above, for example, he notes that the study was unpublished. In a corresponding footnote, he explains that the authors didn’t publish the study because they feared personal attacks by other bite mark analysts (and presumably, people like Melissa Mourges.) He adds the snide comment: ” . . . being thin-skinned is not an excuse for refusing to hold up one’s research to professional scrutiny.”

That isn’t quite what happened. The study’s authors, Iain Pretty and Adam Freeman, agreed not to publish the study at the request of the ABFO. The organization’s more strident members wanted time to conduct a follow-up study that they hope will vindicate their field. Pretty and Freeman agreed. In other word, they didn’t refuse to publish their study out of fear of scrutiny. They agreed to hold off on publishing it as a courtesy to the very forensic analysts that Ferrari is defending.

I would add here that Freeman is also the new president of the ABFO. And though he and Pretty agreed not to publish the study, they did release it to the public. Two sources tell me that this decision nearly resulted in the more strident members of the ABFO filing ethics charges against their own president-elect, similar to the charges against bite mark skeptic Michael Bowers. Pretty isn’t a member of the ABFO, but he too was subjected to disparaging comments about his ethics and honesty from members of the organization.

Ferrari also dismisses the comments by Jo Handelsman, assistant director for the White House Office on Science and Technology. Earlier this year, Handelsman called for the “eradication” of bite mark analysis from the courtroom. In his memo, Ferrari sniffs, “This is an extreme view, not borne out by evidence, and should not be given any weight by the Court.”

Ferrari closes by assuring Judge Wiley that though they are withdrawing the bite mark evidence, it’s really only due to their concern over how long Clarence Dean has been in custody without trial, and their desire to spare Judge Wiley “needless effort.” (How gracious of them!)

Meanwhile, since Wiley’s September 2013 upholding bite mark evidence, two more people convicted based primarily on such evidence have been exonerated and freed. Between them, they had served 45 years in prison. Earlier this year, a Pennsylvania judge also threw out another conviction. And in Mississippi, the state’s supreme court has granted a hearing on the admissibility of bite mark analysis to death row inmate Eddie Lee Howard. (That court has shot down challenges to bite mark evidence numerous times in the past.)

The Manhattan DA’s office has been among the most vocal supporters of bite mark evidence. That office now appears to be on the defensive. That’s a good sign. But it comes only after four decades of bite mark evidence being used to win convictions. Here’s the nub of the problem: So far, every scientific organization and scientist to officially weigh in on bite mark evidence has determined that it lacks any scientific foundation, and shouldn’t be used in court. And so far, every court to hear a challenge to the scientific validity of bite mark evidence has rejected that challenge. That seems like a pretty compelling reason to rethink our practice of entrusting judges to be the gatekeepers of scientific evidence.