Bite Marks

The use of bite mark evidence began around 1870 with the Ohio vs. Robinson case.19,20 The case involved A.I. Robinson, a well-regarded member of his community, who was suspected of murdering his mistress. There were five distinct bite marks located on the victim’s arm which revealed five maxillary anterior teeth.21 Robinson happened to only have five maxillary anterior teeth, which Dr. Taft, a dentist, testified in court that Robinson’s dentition matched the bite marks from the victim.21

A bite mark is known as the registration of the cutting edges of teeth on a substance caused by a jaw closing.22 The scientific premise regarding bite mark analysis is stemmed from the fact that the human dentition is not identical from person to person.20 Bite marks are as specific to a person as DNA or fingerprint analyses, similarly, no two individuals will have the exact same dentition in regards to shape, size and alignment of teeth.20

Bite marks are either left on the victim (by the attacker), on the perpetrator (by the victim of an attack) or an inanimate object found at the crime scene.21 Human bite marks on victims are most often found on the skin and soft tissue areas of all parts of the body.21 Area bite marks on female victims are most often found on the breasts and legs produced during sexual attacks.21 On males the bite marks are commonly seen on the arms and shoulders.23,24 When a person is in defensive circumstances, such as when the arms are held up to ward off an attacker, the arms and hands are often bitten.13 Bite marks are often found on children who are abused.19,22

The duration of a bite mark is determined by the magnitude and how long the victim had been bitten.22 Human bite marks are described as an elliptical or circular injury that records the specific characteristics of the teeth.25 The bite mark may be in the shape of a doughnut with characteristics recorded around the perimeter of the mark.13 Also it may be composed of two U-shaped arches that are separated at their bases by an open space. Typically the diameter of the injury is from 25-40mm.13 Often the injury has a central area of bruising seen within the bite mark.13 This is caused by pressure from the teeth as they compress the tissue inward from the perimeter of the mark.13

Guidelines have been established for bite mark analyses by the American Board of Forensic Odontology (ABFO) (Table 2) for the ABFO Guidelines.21,26 When collecting dental evidence, a description of the bite mark in regards to demographics, location, shape, size, color, type of injury and any other information needs to be recorded.21,25,26 The collection of evidence from the victim includes photographs, salivary swabbing, impressions and tissue samples.21,25,26 Even collection of evidence from the suspect(s) is needed, which includes history, photos, extraoral examination, intraoral examination, impressions, sample bites and study casts.21

Table 2. ABFO Guidelines for the Collection of Victim Evidence.13,29
  • Photography
    Orientation and close up photographs should be obtained with and without the presence of a scale placed adjacent to the bite mark. The scale must be positioned within the same plane as the bite mark and should include a linear and circular reference to aid in eliminating possible distortion. The film resolution should be high quality with proper color balance. Serial photographs are recommended in living victims.
  • Salivary Swabbing
    Saliva swabs should be collected in circumstances in which the bite site area has not been altered from the time when the bite was inflicted.
  • Impressions
    Impressions of the bite site area should be taken when there is sufficient surface detail which may yield beneficial information. The material used must meet the American Dental Association specifications and suitable support should be included for proper support and reproducibility of the body site contour.
  • Tissue Samples
    Tissue samples should be retained if it appears it may yield useful information.

Upon collection of dental evidence, the forensic odontologist analyzes and compares the bite marks.21,26,27 Studies have been performed in an attempt to find the simplest, most efficient and most reliable way of analyzing bite marks.27 Early forensic investigators analyzed marks left by dental casts in wax, clear overlays, and other mediums.27 Others attempted to simulate the consistency of human tissue by using articulated dental models to “bite” baker’s dough and sponge rubber.28 The ABFO has guidelines established for bite mark methodology to preserve bite mark evidence.29,30 Considerations that need to be made when photographing and documenting the bite site are lighting and the utilization of a scale in the photo to provide an accurate account of the bite site size.13,25,26,29 The methods for comparing bite mark evidence are the use of overlays, test bite media, comparison techniques and technical aids employed for analysis.13,21,29

There are factors that may affect the accuracy of bite mark identification which include time-dependent changes of the bite mark on living bodies, effects of where the bite mark was found, damage on soft tissue, and similarities in dentition among individuals.27 Elasticity and the inflammatory process of human tissue hinder the identification process of bite mark registration.27 Placement of the limb in the exact position when the attack occurred is necessary to recreate the correct bite relationship; this may not always be known in the case of a decedent.27

In regards to famous bite mark cases, Ted Bundy the serial killer would be the one that comes to mind. Dr. Richard Souviron was the forensic dentist, who was requested to come to Tallahassee, Florida to examine evidence that had been discovered on the body of one of the victims from the Chi Omega sorority house in January of 1978.23 Dr. Souviron, by accepting a part in the case, became part of the legal process regarding the case.20 Therefore, Dr. Souviron was responsible for thorough documentation of the evidence.20 He found, upon arrival to view the evidence, the tissue was from a breast and buttocks that had been excised and placed in fluid without retaining rings.23 Though the materials were of limited value, Dr. Souviron was able to determine the person who bit the victim had poorly aligned teeth.23 This information assisted in establishing probable cause which was necessary in order to obtain a search warrant; this warrant allowed Dr. Souviron to take dental impressions, bite records, and photographs of Ted Bundy’s dentition.23 Then he provided a photograph of the bite injury (Figure 4).11,23

Figure 4. Dr. Richard Souviron presents evidence at Ted Bundy's appeal trial - Tallahassee, Florida.
Dr. Richard Souviron presents evidence at Ted Bundy's appeal trial - Tallahassee, Florida.
Mark Foley - Photographer
Source: http://www.floridamemory.com/items/show/133904

In addition, Dr. Lowell Levine and Dr. Norman Sperber also examined independently the evidence and all three examiners concluded the evidence did implicate Ted Bundy as the perpetrator of the bite marks.11,23 Once the evidence was admissible, Dr. Souviron presented a series of slides to the grand jury and ended up testifying at the trial.p11,23 Ted Bundy was convicted on seven counts and sentenced to death.11,23