In my series on bite mark evidence last February, I pointed out that while the practice of bite mark matching has been roundly criticized by the scientific community for lacking any of the basic principles of the scientific method, some critics of bite mark evidence were concerned that the subcommittees under NIST that were charged with looking into the field had been stacked with bite mark analysts and their allies.
But this week, the fate of bite mark evidence took a much different turn. In her speech to open the conference, Jo Handelsman, assistant director of the White House Office of Science and Technology Policy called for the “eradication” of bite mark evidence. I’ve obtained an audio clip of her speech. Here’s a transcript of the relevant portion:
Two of the elements highly focused on in the report are that we need to have highly consistent data and methods, and we need to have a high degree of certainty in the results that we obtain in forensics science when we’re linking an individual to a crime scene or sample.There are a number of examples where we haven’t lived up to that standard of both certainty and consistency.One of the studies . . . is really quite disturbing. They showed variable conclusions among expert practitioners about whether in the example of bite marks the injury was in fact a bite mark, whether the marks were made by human teeth . . . or by animals, and whether the images of those marks were suitable for analysis.And interestingly, those who had more experience, the more experienced practitioners, showed more variability between the practitioners — they came to less agreement than the less experienced practitioners. So where in many fields we might say, well we just need people who have more experience, more of a feel for the data, in fact it goes the wrong way in forensics.And then they found that many of the practitioners show no consistency. It wasn’t as if some practitioners were consistently conservative and others made less conservative assessments. They were all over the place.Suggesting that bite marks [should] still be a seriously used technology is not based on science, on measurement, on something that has standards, but more of a gut-level reaction. Those are the kinds of methods that have to be eradicated from forensic science, and replaced with those that come directly out of science, and have the ability to stand up to the standards of scientific evaluation.
Handelsman is referring to the study first reported last April here at The Watch. That study was conducted by the American Board of Forensic Odontology, essentially an advocacy group for bite mark analysts. When the results showed a lack of consensus among these experts about basic attributes of the bite mark samples they were given, it basically confirmed what critics of the discipline have been saying for years. (It’s also probably why the group tried to keep the results under wraps.)
Chris Fabricant, a director of strategic litigation for the Innocence Project who specializes in bite mark cases, says it’s difficult to overstate the significance of a senior White House policy adviser on science issues calling for the end of a major field of forensics. “It’s unprecedented,” Fabricant says. “It’s necessary, and she’s completely right. But this has never happened before.”
The California Innocence Project is also representing William Richards, a California inmate currently mounting an important challenge to bite mark evidence. Last month, 34 scientists and forensic specialists submitted an amicus brief on Richards’s behalf. The brief concludes:
The scientific community, and society generally, expect that before being offered to courts, and before courts grant broad and unqualified admission, the claims for a field’s techniques will have been validated. This validation has not happened for bitemark identification. Moreover, recent reviews of the field’s claims, as well as recent empirical findings, have underscored the lack of reliability and validity of the most fundamental claims about the ability of forensic dentists to identify the source of bitemarks on human skin.
With so much of the scientific community now firmly denouncing bite mark evidence, surely we’ll soon start to see convictions overturned, right?
Not necessarily. This ultimately comes down to the courts, and so far, the courts haven’t shown much interest. For reasons both unclear and unwise, we’ve left it up to judges who were trained in law, not science, to determine the scientific validity of forensic evidence. This has proven catastrophic for the fair administration of justice. For decades, judges have allowed juries to be misled by impressive-sounding witnesses who have fed them unsubstantiated nonsense about the ability to match fiber, tool and ballistics patterns; the uniqueness of bite marks, fingerprints and other biological markers; and about the degree of certainty in their conclusions. Appeals courts have then been reluctant to second-guess trial court judges’ decisions. In some instances, such as Shaken Baby Syndrome, the scientific consensus has changed, and the courts are just starting to catch up. But in others, like bite mark evidence, fiber matching, and other pattern-matching fields, there was never any scientific consensus in the first place.
As I pointed out in the series on bite mark matching, some appeals court decisions have gone into great detail to explain why a given field of forensics was legitimate and authoritative in upholding the conviction of a defendant who was later exonerated. And some of those rulings are still good law. In other words, a defendant was convicted due to the testimony of a forensic expert who claimed that his “science” showed the defendant, and only the defendant, could have committed the crime. That conviction was later upheld by an appeals court in an opinion that explained in detail why the expert and his methods were legitimate and reliable. The defendant was later exonerated by DNA testing, thus demonstrating that the expert and his methods couldn’t possibly be reliable. And yet the original appeals court ruling upholding the admissibility of that variety of forensic evidence is still the controlling case law on the matter. These cases alone demonstrate the wholesale failure of judges in upholding their role as the criminal justice system’s gatekeepers of scientific evidence.
The comments from Handelsman — one of the president’s top science advisers — are important, as is the willingness of more and more scientists to speak out on these matters. So too are the comments about bite mark analysis from federal appeals court judge Alex Kozinski in his recent article for the Georgetown Law Review.
But the problems with bite mark evidence have been known for decades. There was never any scientific evidence to back up the claims of bite mark analysts. And yet not only did the courts continue to allow bite mark matching into evidence, every single time a defendant challenged its validity, that defendant lost. William Richards in fact lost his first appeal to the California Supreme Court even though the expert who testified against him at trial later disavowed his own testimony. (His new challenge comes after the California legislature passed a law in response to that ruling.)
Judges aren’t scientists, and neither are most jurors. Like most of the rest of us, they can be swayed by such non-scientific factors as a witness’s charm, demeanor and tone. Good scientists don’t speak in absolutes, they talk about probabilities. That can make them sound wishy-washy, and thus less convincing, than a charlatan who is willing to make assertions without equivocating.
Handelsman’s comments are progress, but they also further expose the core problem with scientific evidence: If not a single court in the country to date has been able to rule against a self-evidently absurd field like bite mark matching, why should we continue to entrust the courts to arbitrate the scientific validity of other evidence?