Bitemark Analysis is a Critical Component of Forensic Odontology
By David A. Williams DDS, MS

Forensic dentistry, or forensic odontology as it is often called, is the correct examination, handling and presentation of dental evidence in a court of law.¹ Forensic odontology is comprised of three parts: clinical and oral examinations, identification of remains and the analysis of bitemarks.

Clinical and oral exams are used primarily in cases of suspected malpractice or personal injury. The forensic odontologist examines the patient, reviews the clinical record and renders an opinion regarding the appropriateness of treatment.

Dental enamel is the hardest substance in the human body and is extremely resistant to most destructive forces including chemicals, heat and physical trauma. Human remains can be burnt, skeletonized, saponified or traumatized and still the dental information remains. Information taken post mortem is compared with antemortem data and a conclusion is drawn as to a match. If they do, then there is a definitive identification. There need not be the entire dentition present to produce a match, but there must be enough information both ante-and postmortem.

Analysis of bitemarks is evolving within forensic odontology. Here, information is taken from a suspected bitemark and compared to the dentition of an individual. The bitemark may be on a victim or perpetrator, on the skin, or in some other object. The medium that the bitemark is in is usually not stable so it is imperative that information be collected at the earliest possible time.

Any injury that is oval, elliptical or semi-circular should be considered a bitemark until proven otherwise. They may be recent and be red in color, they may be older and have undergone the stages of bruising, or there may be an avulsion or tearing of the tissue. They may appear to have individual teeth marks or they may not. They can be single or multiple. Clothing or other interposing material overlying the area may change the appearance of the bitemark, and the tone or elasticity of the tissue may alter the appearance. Positioning of the biter and victim may change the way the bitemark looks.

In the living victim, the most important object is to treat any wounds that are life threatening, but as this is done, attention must be given to the possibility that there may be a bitemark in an area that if improperly preserved, will be lost forever.

Studies have shown that bitemarks were features of sex-related crimes, abuse cases and crimes of physical assault, but this potentially key evidence is one of the least used tools available to law enforcement, mostly because they go unrecognized or if recognized there is a question about how to collect information and who can analyze it.

Vale² found that there was bitemark evidence in about 40 percent of cases of sex-related crimes, child abuse cases, and cases involving other types of physical altercation. In another study where location of bitemark was studied, the most frequent site of the bitemark was the breast (33 percent), arm (19 percent), genitalia (8 percent), back (7 percent) and face (5 percent).³

Once a bitemark is identified, the information it provides must be collected. Initially, non-invasive procedures are instituted. Photographs are taken from a distance for orientation, then close-up without and with a ruler present (ABFO No. 2 scale is preferred in most cases) with visible light. Infrared and ultraviolet photographs can often be of assistance because the difference in wavelength of light can elucidate details that may be missed if only visible light is used. Photographic procedures should progress over a period of time that may exceed a month, since as the injury heals, other information may become evident.

DNA evidence can be obtained from the bitemark area following the non-invasive procedures. A sterile cotton swab is moistened with sterile saline or distilled water and the skin is gently swabbed in a circular motion starting from the center. The swab is then labeled and put aside to air dry. A second dry swab is then used to repeat the procedure over the area, labeled and air-dried. The entire procedure is repeated at another nonaffected site for a control. The swabs are then given to the evidence technician to follow the normal chain of custody.⁴

In some instances, the bitemark can be seen as an indentation in the skin. In this case the odontologist can make an impression of the site to memorialize the injury. The impression is most commonly made with standard dental materials. A sturdy backing material is fashioned to support the impression, and then impression material is flowed onto the site and allowed to set. The impression is removed and poured in dental stone.

In the case of a deceased victim, the odontologist can fabricate a ring and attach it to the area surrounding the bitemark. The tissue can then be excised and placed in a fixative solution for future evaluation.

When a suspected biter is identified, the odontologist may make his exam after first obtaining a search warrant and waiver of body search. The exam begins with a complete medical history. After appropriate safety precautions are taken the clinical exam may commence. This should include the dynamics of the hard and soft tissues of the facial area as well as static information such as dental restorations present, mobility of teeth and fractured or missing teeth. Multiple dental impressions are made using approved materials and these are poured in dental stone. Bite relationships are recorded. All of the procedures as well as the dentition should be photographed. Materials should be marked appropriately and sealed as exhibits according to the chain of custody.

Using materials obtained from the victim and the suspect(s), the information is compared.

Metric and pattern association analysis are used. In metric analysis, measurements are made such as length, width, and depth of markings and noted as well as spacing and rotation of teeth. Detailed analysis of other comparative points is made. Pattern association is most often obtained when overlays of the dentition of the suspect are fabricated using accepted procedures and compared with photographs of the injury that have been produced at a 1:1 ratio.

The odontologist makes a conclusion regarding the degree of concordance among the exemplars of victim and the suspect(s). This conclusion is usually one of the following categories: the evidence is of on evidentiary value, the suspect(s) is/are ruled out, it is improbable that the biter is the suspect(s), it is possible that the suspect(s) is/are the biter, it is probable or very probable that the suspect(s) is/are the biter, and it is a reasonable medical certainty that the suspect(s) is/are the biter.⁵

The opinion of the forensic odontologist is then considered with the other appropriate evidence including the DNA evidence to aid in the determination of guilt at trial.

There are four national forensic dentistry organizations. The American Society of Forensic Odontology has approximately 1,000 members who have an interest in forensic dentistry, but are not necessarily dentists. The American Academy of Forensic Sciences has an odontology section that consists of approximately 500 members. Only dentists may be members of this section at this time. The American Board of Forensic Odontology has less than 100 active members and is the most restrictive of the organizations, requiring case presentation and examination for membership. The American College of Forensic Examiners has about 5,000 members in 11 sections including dentistry.

Bitemark testimony can prove to be pivotal in a trial, but if the bitemark is not initially recognized, or if the information is not gathered and processed properly, this testimony will never be available to the court.

David A. Williams, DDS, MS, is a practicing general dentist, is the president of the Maryland State Dental Association, is a consultant with the Maryland Office of the Chief Medical Examiner and is the Franklin County (Pennsylvania) coroner.

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