Bite Mark Analysis

Criminal cases many times call for the examination of evidence that can tie a suspect or victim to a crime scene or to one another. These physical traces frequently include blood and other bodily fluids, hair, fibers, and even bite marks. Here we will focus our attention to the latter and its accuracy, as it applies to the field of forensic science referred to forensic odontology or forensic dentistry. Forensic odontology is the field of forensic science dealing with the recognition of unique attributes present in each individual’s dental composition.

This branch of forensics relies heavily on extensive and detailed knowledge of the teeth, jaws, and dental anatomy possessed by a dentist. In addition to this knowledge, the forensic dentist must be well-versed in the interpretations of radiographs, pathology, charting, and types of dental treatment. The forensic dentist is dutifully responsible for the proper handling, assessment, and evaluation of dental evidence in the name of justice. The dentist is the key to identification based upon the distinctive features present in the dental structures of each individual. Identification of deceased individuals who cannot be identified by other means, identification of human remains, identification of victims in mass fatalities, assessment of bite mark patterns, and age estimation using teeth are all part of the role of forensic odontologists as well.

Identification of an assailant by comparing a record of their dentition with a record of a bite mark left on a victim and the presentation of bite mark evidence in court as an expert witness are also done as part of the job. Bite mark comparison is one of the major and newer parts of this forensic discipline that has been evolving since the 1970s and has played a major role in many cases and the convictions of many criminal including the infamous Ted Bundy who was convicted solely on evidence of a bite mark analysis. However, recently, there has been a lot of debating around the accuracy of a bite mark comparisons and if it can truly assist in accurately identifying suspect as the biter in an attack. For example, in 1991 Ray Krone, a former letter carrier without a criminal record, honorably discharged from the U.S. Air Force was charged with taking the life of a Phoenix cocktail waitress, Kim Ancona. A body examination revealed that she had been stabbed eleven times and bitten on the left breast and on her neck. Forensic evidence, or lack of it, indicated that there were no fingerprints and other bodily fluids although there was indication that she had been sexually assaulted. There was little evidence that tied Krone to the crime except for evidence of the bite mark on the victim’s breast, which a state forensic odontologist, Dr. Raymond Rawosn, said matched his very distinct teeth. The bite mark testimony of Dr. Rawson convinced the jury that Krone was guilty and he was convicted.

During the time of prosecution, forensic DNA technology was not generally available, but once it was, Ray Krone was proved innocent of the crime. A DNA test not only established that he was not involved in the fatal stabbing, but that also identified the true perpetrator – a person already incarcerated on another unrelated offense. After being cleared by DNA, Ray Krone walked out of the Arizona State Penitentiary at Yuma on April 8, 2002, a free man.

In another case, Ricky Amolsch, 38, ended up in jail for ten months over a mistake that a forensic dentist made. His girlfriend, Jane Marie Fray was gruesomely stabbed twenty-two times and an electrical cord was wrapped tightly around her neck. She was also bitten near her left ear. Amolsch was arrested, photographed and fingerprinted. The chief forensic odontologist for Wayne and Oakland Counties, Dr. Allan Warnick’s claims of a bite mark match persuaded the district judge to sign a capital warrant. The preliminary hearing relied on this evidence alone with the forensic dentist, Dr Warnick, giving a compelling testimony. Since Amolsch was not eligible for bond, he had to stay in jail until his trial, and during that time, he lost his home, his savings and his children.

After one of Warnick’s other cases was challenged, officials re-examined Amolsch’s case. Dr. John Kennedy, another forensic dentist, reviewed the case and gave a second opinion that it was someone else, not Amolsch, who had bitten Fray’s face. Two other forensic dentists agreed and Amolsch was released from jail. It is true that a human bite mark inflicted by an attacker on the skin of a victim may leave a definitive identifiable pattern that can be identified as being made by a certain set of teeth. If a suspect is apprehended his teeth are reproduced by taking impressions of the teeth and pouring plaster into the impression, thus producing a plaster model. The plaster models of his or her teeth are then put on a scanner and scanned to make a digital image. A tracing of the biting edges of the teeth is then made either using the omputer or tracings from the printed image. This tracing is then superimposed on the bite mark photo, either manually or electronically using a scanned image of the bite mark, to determine if a match can be made.

Bite mark analysis is based on two postulates: a) the dental characteristics of anterior teeth involved in biting are unique amongst individuals, and b) this asserted uniqueness is transferred and recorded in the injury.

However, some bites are forceful enough to leave a good impression, others are not. A bite might penetrate the skin, but often only leaves bruising—and sometimes the blood marks of a bruise are mistaken for the impression of a tooth. It also seems to be the case that skin gets distorted when bitten or the teeth slide during the act of biting.

Furthermore, the level of distortion tends to increase after the bite mark was made. A studies suggest that for the bite mark to be accurately analyzed, the body must be examined in exactly the same position it was in when the bite occurred which can be a difficult if not an impossible task to accomplish. In addition, bite mark analysis is also controversial because dental profiles are subject to change. The loss and/or chipping of teeth, or the alteration of arch configuration through a variety of procedures, such as the use of braces, is common in human populations. The onset of oral diseases such as dental caries has been shown to alter the arch and tooth configuration and must be taken into account when comparing a dental profile to the bite mark after a significant amount of time has passed since the mark was made.

All of these variables affect the validity of a bite mark analysis and trying to identify an biter through the uniqueness of his or her dentition. One particular case that highlighted the lack of uniqueness in bite marks involved two suspects accused of attacking a man that had sustained a bite mark injury. Two separate forensic dentists, one representing the prosecution and one the defense, were brought in to analyze the mark. They reported conflicting results. One found the mark to come from suspect A and the other said it was from suspect B. This disagreement resulted from the fact that even though the two suspects had dental features making them unique, the bite mark itself was not detailed enough to reflect them. Therefore, the mark could have reasonably come from either of the men.

The equivocal outcome demonstrated in the case emphasizes the difficulty in proving uniqueness. In conclusion, not all bite marks have the level of forensic value necessary to identify just one individual. Now, individual characteristic within a bite mark or in a person’s dentition is a distinguishing feature, trait, or pattern. Individual dental characteristics are reported to be features that are unique to an individual variation within a defined group. The presence of worn, fractured or restored teeth is valued as unique features. If a bite mark possesses the reflection of such a feature(s), the degree of confidence in a match increases. It is actually counter-intuitive to assume enamel chips, fractures, and dental restorations are always inherently unique. The shape of human teeth is quite constant in nature and their changes over time are based on common events.