Why It’s So Hard to Rid the Courts of Junk Science

Steven Mark Chaney had nine alibi witnesses. From morning to night, his movements on June 21, 1987, were well documented. Nonetheless, he was convicted and sentenced to life in prison for the murders of John and Sally Sweek, drug dealers Chaney had previously bought cocaine from and to whom he supposedly owed $500 — his alleged motive for brutally murdering them that day in their Dallas, Texas, apartment. There was nothing to tie him to the crime, save for a supposed bite mark found on John’s arm that several forensic dentists said matched Chaney’s dentition.

Bite-mark evidence rests on a deceptively simple foundation: that human dentition is as unique as DNA; that skin is a suitable substrate to record that alleged uniqueness; and that forensic dentists are adept at identifying wounds, usually bruises or abrasions, that have been made by teeth and then determining whose teeth did the biting. As it turns out, none of these claims are supported by any research, and today bite-mark evidence, which has led to at least 35 wrongful convictions and indictments, is considered junk science.

But while science has discredited the practice, bite-mark analysis is still admissible in many courts. Once a form of evidence is accepted by a judge, legal precedent makes it incredibly difficult to keep even the most questionable forensic practices out of court.

When Chris Fabricant joined the Innocence Project in 2012 to head up its new strategic litigation division, he made it his mission to eradicate bite-mark evidence from criminal cases. In his new book, “Junk Science and the American Criminal Justice System,” Fabricant charts the rise and fall of bite-mark analysis through the group of dentists who created the practice and three of the wrongful convictions that followed, including Chaney’s. He was finally exonerated in 2018. In an interview with The Intercept, Fabricant discussed how bite-mark evidence and other questionable fields of forensic science made their way into the criminal justice system, why they’re so difficult to eradicate, and what can be done about it. This interview has been edited and condensed for clarity.

A lot of people don’t realize that almost all forensic science is created by police. It’s “science” in service of law enforcement. Can you talk about how bite-mark evidence fits into this framework?

I’ve spent 10 years litigating the admissibility of this evidence and finding all the many victims of this junk science. But where did it come from? Who invented this and why? What was unusual about the exploration of bite-mark evidence in junk science is that you can really find the source. The origin story is available in a way that is hard to really pinpoint for most other forensic techniques.

I had to file a lawsuit to get access to the American Board of Forensic Odontology archives, and that’s where I found some of the original source material. There was this idea that maybe you can match teeth to bite marks; people are speculating about it, it was starting to get a little bit in the water, there were some seminars, and some dentists were starting to get into it. I cited this article I found that Dr. Lowell Levine had written, a few years before the first bite-mark case, openly saying that there was no science here but lobbying for a role in the criminal legal system. They needed a case, and they found the case. And then they were off to the races.

That’s the Walter Marx case from the 1970s. Tell us about Marx and the impact that case had on the proliferation of junk science in the criminal legal system.

The People v. Walter Marx is one of the most significant legal opinions in forensic sciences ever published, even though it’s somewhat obscure. And the influence of the Marx case is still reverberating today.

Skin cannot record teeth marks or any other type of instrument that created an injury.

Marx was indicted for murdering his landlord. There was circumstantial evidence pointing to Marx, but no physical evidence. And this victim had a bite that almost took her nose completely off. It was a very unusual bite mark because it was in cartilage. Cartilage will hold the pattern of whatever instrument was used to inflict the injury with much more fidelity than skin. Skin cannot record teeth marks or any other type of instrument that created an injury. So it was a perfect case in that way, and all the problems that are associated with interpreting a bruise on skin were not present. It was still junk, but it wasn’t as junky as what we get into later.

Three dentists testified against Marx. He was convicted based on the bite-mark evidence, which the trial judge allowed into evidence, and then what the court says on appeal about that decision is important and implicates a host of other pattern-matching forensics. What did the opinion say?

The trial judge conceded that this technique had not been researched in a laboratory, the fundamental assumptions had not been tested through scientific research or clinical application. It was simply matching teeth to an injury.

Subsequent to that, the reasoning was adopted, and the Marx case was cited by state supreme courts around the country for the introduction of bite-mark evidence. But beyond that, the same reasoning was applied to many other pattern-matching techniques. And pattern-matching techniques cover a lot of ground, right? You’re talking about fingerprints, you’re talking about firearms, tool marks, shoe prints, tire treads, hair microscopy. The thinking that went into that was, this is not really the type of scientific evidence that we need to be concerned about. It’s simple, it’s not really science, it’s just matching things. That line of reasoning has shielded all these unreliable forensic techniques from real judicial scrutiny.

You describe this as “scientifically illiterate case law” that has obscured the need for rigorous scientific inquiry. Because it’s like, if this practice has been sanctioned by the courts, why in the world would anyone go and conduct foundational research into it? So what has been the impact of scientifically illiterate case law on the trajectory of junk science in the criminal legal system?

You don’t have to look any further than the Charles McCrory case in Alabama, which is going on right now, to see the impact of a terrible decision like People v. Marx. Because People v. Marx was cited in an Alabama case, State v. Hadley, in 1987. And that case was used by the trial court to deny McCrory a new trial in 2022 — even though we have more than 35 wrongful convictions and indictments involving bite-mark evidence — which is astonishing. You can draw a straight line from Marx, who was probably guilty, straight to Charles McCrory, who is definitely innocent.

What we have is the difference between law and science. Science is this process that is always moving forward. Hypotheses are abandoned once they’re falsified. And that’s a continuous process, always improving on the knowledge. And law rests on precedent — precedent that doesn’t advance, or if it does, it’s slow.

The process of science in relation to the process of the way law develops are in direct conflict. And if we’re going to use scientific evidence, we have to do a better job of keeping up with science. And that means not introducing forensic techniques in criminal court unless and until they’ve been scientifically evaluated and demonstrated to be reliable.

We should have something like the Food and Drug Administration that is testing these forensic techniques before they’re used to make life and liberty decisions. We do that with aspirin; we do it with toilet paper. We don’t do it with forensic sciences.

Tell me a bit about how you got involved in Steven Chaney’s case.

When I went to the Innocence Project, the strategic litigation department, I was looking for test cases. I was very interested in focusing on bite marks because it was such an obvious form of junk science. I had put out the word to the defense bar across the country, and we took every bite-mark case we could find. And then Dallas public defender Julie Lesser called me about Steven Chaney’s case and said that a dentist had testified that Chaney’s teeth were a one-in-a-million match. And I was like, this is a case that we’re going to litigate.

It was significant that this was a Texas case, because there were two innovations in Texas law that came into play: the Texas Forensic Science Commission and the state’s junk science writ. Tell us about those.

The Texas Forensic Science Commission is the leading forensic science commission in the country, and it’s highly respected because the commission is nonpartisan. It’s outside of the adversarial process; all science should be scrutinized outside of the adversarial process, outside of the criminal courts, because it’s hard to separate sense from nonsense in that setting.

The complaint that we filed with the commission was like, take a look at Steven Chaney’s case and this outrageous testimony that was proffered at trial. And that led to not only the findings related to Steven Chaney’s case, but the findings related to all bite-mark evidence. They recommended a moratorium on bite-mark evidence unless and until it can be demonstrated reliable and practically validated. It hasn’t happened. And it will never happen.

Texas Statute 11.073, which became known as the junk science writ, was the first of its kind in the country. It allows prisoners who’ve been convicted on allegedly scientific evidence to go back into court if the progress of science demonstrates that the scientific evidence that was used in trial has been discredited, and/or if an expert witness has recanted their testimony. So it provides a very important avenue of relief for people like Steven Chaney who did not have conclusive DNA but were factually innocent and were convicted on junk science.

Your junk science writ got Chaney’s case back in front of Texas’s Court of Criminal Appeals. What did they say?

They said that the bite-mark evidence that once appeared to be conclusive of Steven Chaney’s guilt no longer proved anything and that Steven Chaney is actually innocent. That was progress, and it was important that it was from Texas, meaning that they’re not bending over backwards to free anyone. Texas was willing to look back on a conviction like Steven Chaney’s, which was affirmed based on the bite-mark evidence on the initial appeal. So to go back and take another look at a conviction that the same court had affirmed, to correct the record and then do the right thing, was a great day for justice in Texas, and that’s reverberated around the country.

It was after the Steven Chaney case that the dominoes really started to fall. I don’t think that Eddie Lee Howard is exonerated off death row without the Court of Criminal Appeals opining in the Chaney case, for example — and the exonerations that have followed from Steven Chaney’s case, like Gilbert Poole’s, more recently, and the Robert DuBoise exoneration in Florida.

And that’s one of the things — go back to what we were talking about, legal precedent. I sometimes make this point about how many of the precedent-establishing cases in state high courts where the law is still good law and cited by prosecutors, the human beings that were prosecuted in those cases were actually innocent. Levon Brooks is the precedent-establishing case in Mississippi. Gary Cifizzari, precedent-establishing case in Massachusetts. Robert Lee Stinson, precedent-establishing case in Wisconsin. All three exonerated in the last few years.

And the courts allowed bite-mark evidence in all three of those cases. You write that any case resting on junk science is inherently unreliable. If that’s so, what is the duty to correct those cases?

What jurors are often told by judges before they get a case is that a trial is the search for the truth. And we know that the search for the truth is never advanced through the use of junk science. The idea that you can introduce total speculation, put that in front of a jury, and still have confidence in that verdict is whistling past the graveyard. You want to have this faith that even if you introduced unreliable evidence that the verdict is nonetheless reliable. What the Innocence Project cases show, time and time again, is that’s just not so.

In the American criminal legal system, we require proof beyond a reasonable doubt. If some of that threshold was met through false testimony, our system of justice does not allow those verdicts to stand, period. By and large, courts refuse to acknowledge the reality that so many of these techniques that have been used for so long are not reliable, and they’ve been grossly exaggerated and sold to jurors to gain convictions. So the duty to correct is to go back to these cases, concede error, waive any of the procedural barriers that are often erected to prevent actual examination of the facts of the case and the fairness of the trial, and allow the proceedings to go forward, grant new trials, and have trials free of junk science. That’s the duty to correct.