Statistical evidence for the similarity of the human dentition

Bush, M. A.
Bush, P. J.
Sheets, H. D.
Journal of Forensic Sciences, Vol. 56 Issue 1, Pages 118-123
Recent scrutiny of forensic science has focused on unreliability of expert witness testimony when based on statements of individuality. In bitemark analysis, assumptions regarding uniqueness of the dentition have been based on use of the product rule while ignoring correlation and nonuniformity of dental arrangement. To examine the effect of these factors, two separate sets of scanned dental models (n=172 and n=344) were measured and statistically tested to determine match rates. Results were compared to those of a prior study. Seven and 16 matches of the six anterior lower teeth were found in the respective data sets. Correlations and nonuniform distributions of tooth positions were observed. Simulation tests were performed to verify results. Results indicate that given experimental measurement parameters, statements of dental uniqueness with respect to bitemark analysis in an open population are unsupportable and that use of the product rule is inappropriate.


A paradigm shift in the analysis of bitemarks

A paradigm shift in the analysis of bitemarks Original Research Article
Forensic Science International, Volume 201, Issues 1-3, 10 September 2010, Pages 38-44
Iain A. Pretty, David Sweet
journal homepage:

There have been major changes in the approach to and philosophy surrounding bite-mark analyses in
recent years. This has resulted in a paradigm shift. Concentrating on three important areas, this review
aims to describe the shift in the bite-mark paradigm following recent research studies, the increasing
numbers of wrongful convictions that are associated at least in part with bite-mark analyses, and the
publication of the United States National Academy of Sciences report entitled Strengthening Forensic
Science in the United States: A Path Forward. The article provides an update on the current context and
status of bite-mark analysis. Given the present combination of critical elements, a new level of caution
that includes the use of a careful scientific approach to casework, increased reproducibility of
conclusions by independent analysts, and hypothesis-driven research is needed. Bitemarks have the
ability to exonerate the innocent, protect children from harmful caregivers, and convict the guilty.
However, they also may be the enemy of natural justice.

Judges growing critical of ‘CSI’ evidence

Judges growing critical of ‘CSI’ evidence

By Dan Vergano, USA TODAY

The CSI: Crime Scene Investigation series makes it look easy, but forensic science doesn’t always do so well in the courtroom with judges. And a pair of upcoming studies in the Journal of Forensic Science suggests some judges’ suspicions are growing about the shakier types of scientific evidence.

In the studies led by Mark Page of Australia’s University of Newcastle, legal experts looked at U.S. cases since the 1993 Daubert v. Merrell Dow Pharmaceuticals Inc. and 1999 Kumho Tire Co. Ltd. v. Carmichael court decisions that set higher standards for scientific evidence in criminal cases. Previously, past use of a technique, such as fingerprints or ballistics, had been sufficient to allow their use in the courtroom. But the Daubert and Kumho decisions had allowed defense attorneys to challenge the reliability of the techniques and the experts championing them, on scientific grounds:

“After Daubert and Kumho, many scholars assumed that a large proportion of forensic evidence presented in criminal and civil courts across the country would now be subject to renewed judicial scrutiny. However, some quickly realized that the real question was not whether legal academics concerned with the reliability of forensic science could interpret Daubert to justify the results they desired, but whether judges would do the same. Studies on the admissibility of forensic science since the Daubert decision have revealed that courts across the United States have felt its influence, even in those jurisdictions that have not explicitly adopted a Daubert standard. Several authors have noted that ”some forensic sciences have been with us so long, and judges have developed such faith in them, that they are admitted even if they do fail to meet minimal standards under Daubert”. The courts thus still appear extremely reluctant to deny the admission of forensic science evidence testimony in both civil and criminal trials. The legal reasoning by which forensic science evidence is admitted, characterized by some as ”judicial gymnastics,” has also been the subject of much criticism,” says the first study.

In addition, scandals at police crime labs and a critical 2009 National Research Council report have also called forensic science (aside from DNA analysis) into question. So, the studies look at how judges are sizing up scientific evidence. The bottom line is that some are growing skeptical, but probably not enough.

In the first analysis, the team looked at 551 cases from 1991 to 2008 where defense lawyers challenged forensic evidence, particularly the 81 cases where judges threw out some or all of it. The leading cause of exclusion was the lack of reliability (36%) for techniques such as document analysis followed by (24%) expert witnesses making inappropriate statements. Says the study, “it is clear that there is a sizable proportion of forensic identification evidence that is failing to meet evidentiary standards in U.S. courts. It is also apparent that in such cases, the reliability of forensic identification science evidence, encompassing the concerns regarding the discipline’s underlying theory, the expert’s testimony, and their methodology, accounts for the majority of judges’ concerns regarding its admission.”

In the second report, the team looked at the reasons for those exclusions, findin that poor casework and unreliable techniques are increasingly chipping away at judge’s acceptance of some standard kinds of forensic evidence, such as custom experiments by experts or handwriting analysis. “Reliance on general acceptance is becoming insufficient as proof of the admissibility of forensic evidence. The citation of unfounded statistics, error rates and certainties, a failure to document the analytical process or follow standardized procedures, and the existence of observe bias represent some of the concerns that have lead to the exclusion or limitation of forensic identification evidence,” concludes the study.
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AWARD Winning Film Documentary Tells About the Tragic Effects of Non-DNA Bitemark Evidence

By Dr. Mike Bowers

“Mississippi Innocence” tells the story of 2 good men charged and incarcerated solely on faulty bitemark evidence for decades by the District Attorney of Noxubee Country Mississippi, Forrest Allgood. Produced and directed by faculty at the University of Mississippi this award winning documentary records Kennedy Brewer and Levon Brooks separate journeys within the law enforcement and criminal justice system of Mississippi. After being convicted, their individual strength, family support and sustained claims of innocence twist together and produce a powerful statement regarding the failure of officialdom, investigatory inadequacies, incompetence, and forensic negligence and misconduct. This recent release of this film has been well received and is being introduced into the MS educational system for its value addition to the social sciences and criminal justice. The voice and intent of the film is mirrored in these comments from Tucker Carrington, its producer from the MS Innocence Project.
“[this is] a story that needs to be fully and accurately told, and that needs to have the lessons that can be learned from it taught. Most of the lawyers in this film, not to mention the dentists and other forensic specialists, along with law enforcement, somehow lost their way — and in some way so have we all in failing to hold them accountable — then and now. I truly believe that the legacy of the three plus decades that the two guys spent locked up has yet to be fully realized.”

To see the movie trailer, obtain more movie info and contact the MS Innocence Project regarding screening the film in your area, go to

Bitemark Evidence in the Kunco Case

The bitemark evidence in the Kunco case consisted of a photograph showing a bitemark on the shoulder of the victim. The bitemark evidence became case critical when the 40 pieces of physical forensic evidence recovered at the scene, which included hair, blood and fiber did not link to the suspect John Kunco. The authorities then consulted a board certified ABFO forensic dentist five months after the crime.

The consulting forensic dentist explained that a scale in the photograph is necessary for the bitemark comparison process. The forensic dentist recalled hearing about a technique that Dr. Michael West developed using UV photography to penetrate the skin in order to capture bruising that still exists below the skin. He believed that he might be able to “see” the old bitemark now not visible through the use of UV photography. The forensic dentist consulted a colleague and photographed the area on the shoulder with UV light. It is from this photograph 5 months after the bite to the shoulder that the intricate details of the biter’s teeth are described through “skin reading”.

Click on red text to open new window with files.

Drs. Sobel and David Reports

Materials Made Available to the Odontologists

1) 32 pages of case background information and reports
2) One 8 X 10 photograph
3) Four 4 X 6 photographs.

Color Photo Bitemark Without Scale

Kunco Model Overlay

"UV" Photograph five Months Later

Overlay showing the "uniqueness of individual characteristics and the class characteristics"

Opinions of the Forensic Odontologists

Dr. Sobel’s testimony

I could say that within a reasonable dental certainty, that the bite on the left back shoulder area of Donna Seaman was in fact inflicted by the teeth of John Kunco.

I felt comfortable about this decision because there were no inconsistencies that I could come up with at all and everything fit perfectly.

Now, all teeth in a bite do not always follow exactly the same size relationships, because remember, we’re biting into an elastic surface. It’s the pattern that we’re looking at.

There is no doubt in my mind.

The size relationships, the shape of the teeth … the fractured portions of a tooth, the worn areas, all of these taken together create a fingerprint picture of the individual.

Dental identification next to fingerprints is the most accurate form of identification of an individual.

I then did an acetate overlay in which I traced some of the outlines of these teeth onto the acetate (exhibit 21).

Tooth number 8 tapers upward, there’s a difference in the plane of the surface. Thus there wasn’t any mark visible because it appeared that the head was tilted to the left angle making the bite only a partial bite involving basically the left side of the mouth, upper and lower.

First of all, the plane of the teeth, you can see how this tooth is lower than the others, and any bite would then leave off that particular area. Especially if the head were tilted in this way.

Exhibit 22 – I prepared this overlay to investigate the pattern of the mark. In other words, to see what we could isolate in the way of teeth and uniqueness of individual characteristics and the class characteristics.

I randomly selected approximately 30 sets of models and compared them to the same imprints to see if there were any consistencies that could come up in other individuals easily, although we can duplicate some curvatures of the arch, we could not duplicate all of the individual characteristics.

I felt secure in seeing everything matched perfectly as a group and individually; all the features were consistent.

Dr. David’s testimony

Kunco had a relatively unique set of teeth.

Remarkable consistency between Kunco’s bite pattern and the bite mark on the victims shoulder.

The teeth of the defendant, John Kunco, made the bite mark.

Not only is it consistent, but also it is a remarkable consistency.

There were some inconsistencies in the tracing, which are explained by the dynamics of the bite.

I did not include in the report, an explanation how I did my analysis… its not typically placed in a report.

Next Part 3 – Innocence Project Assembles Team for Review

Dr. Michael Bowers, Dr. David Senn, Dr. Ian Pretty, Dr. David Averill