Bite-mark analysis

DEFINITION: Examination and comparison of wounds caused by biting during physical attacks.

SIGNIFICANCE: The bite marks analyzed by forensic scientists may include marks made by attackers on victims and marks made by victims on attackers. Also, in some cases, crime victims and the perpetrators of crimes leave bite marks on objects found at crime scenes. Bite-mark analysis can sometimes provide important physical evidence linking an offender to a victim or crime scene.

The reliability of the resulting from bite-mark analysis depends greatly on the skill and experience of the forensic odontologist who conducts the analysis. The occurrence of bite marks in criminal cases is not common; when bite marks are found, they are seen most often in cases of violent sexual crimes or child abuse.

Procedures

When investigators that a particular wound is a bite mark, they record every detail about it, including its appearance, color, location on the body, and size, and whether the bite seems to be human or animal. They also photograph the mark from all possible angles, laying a ruler alongside the mark in each photo to show both the mark’s length and its width. If a ruler is not available, another object of known size, such as a coin, is included in the photographs to clarify the size of the mark.

If the indentation of the bite mark is sufficient, an impression is made of the mark before the skin is able to smooth over or change shape. Obtaining a good impression of a bite mark can be difficult, particularly if the skin was distorted before being bitten or the teeth slid across the skin while biting. The suspected bite-mark area is also wiped with sterile cotton swabs to collect any saliva or other evidence left behind by the biter that might yield (deoxyribonucleic acid) for analysis; the swabs are placed in sterile tubes to preserve the evidence.

If a suspect has been identified, a dentist or forensic odontologist then makes an impression of the suspect’s teeth. From this impression, a transparency or computer image of the bite mark that would be left by that suspect’s teeth is created. The dentist also examines the suspect’s bone and muscle structure to determine if any unusual factors are present that would affect the suspect’s bite. Also taken into account in the analysis of a suspect’s bite are factors such as fillings, lost teeth, the curve of the teeth, and any spaces between teeth.

The American Board of has set specific guidelines regarding the presentation of bite-mark evidence in court. In testifying as expert witnesses regarding such evidence, forensic odontologists are held to the standard of “reasonable medical certainty,” which means that they must be confident in their conclusions.

Questionable Evidence?

In a study conducted in 1999, a member of the American Board of Forensic Odontology found that bite-mark analyses wrongly identified the persons who made the bite marks about 63 percent of the time. This study concluded that bite-mark analysis is always subjective and that no standards are accepted across the forensic odontology field.

Some widely publicized cases of men wrongly convicted based at least in part on bite-mark evidence include those of Ray Krone, Roy Brown, and Ricky Amolsch. Krone was convicted of murdering a woman based on a bite mark on the victim’s breast; he was later released when DNA evidence showed another man had left the bite mark. Brown was also convicted of murder but was freed after serving fifteen years in prison when DNA analysis of the saliva left in the bite marks on the murder victim showed that the saliva was not his. Based on the flawed of a forensic dentist, Amolsch spent ten months in jail, during which time he lost his life savings, his home, and his children. He was freed when the work of the same dentist was called into question in another case involving bite-mark evidence.

In 2009, the National Academy of Sciences issued a report on all forensic science disciplines. Bite-mark analysis was severely criticized. By 2023, forensic odontology had revised its approach to the method and established standard guidelines. For example, rather than refer to findings as a "match," experts recommend examiners use phrases such as "can exclude" and "cannot exclude."

Bibliography

Bowers, C. Michael. Forensic Dental Evidence: An Investigator’s Handbook. San Diego, Calif.: Elsevier Academic Press, 2004.

Cardoza, Anthony. "Forensic Odontology and Bite Mark Analysis: Understanding the Debate." Journal of the California Dental Association, vol. 51, no. 1, 2023, doi.org/10.1080/19424396.2023.2210332. Accessed 14 Aug. 2024.

Dorion, Robert B. J., ed. Bitemark Evidence. New York: Marcel Dekker, 2005.

Johansen, Raymond J., and C. Michael Bowers. Digital Analysis of Bite Mark Evidence. Santa Barbara, Calif.: Forensic Imaging Institute, 2000.

Libal, Angela. Fingerprints, Bite Marks, Ear Prints: Human Signposts. Philadelphia: Mason Crest, 2006.