Forensic odontology is the application of dental science to legal investigations, primarily involving the identification of the offender by comparing dental records to a bite mark left on the victim or at the scene, or identification of human remains based on dental records.
Criminals have been known to leave bite mark impressions at the crime scene, whether it be in food, chewing gum or, more commonly, on the victim. When a bite mark is discovered, numerous steps should be taken. Once the mark has been sufficiently photographed, a saliva sample is taken from the area for potential DNA evidence. Casts or moulds can then be made. If another bite impression is found elsewhere or if a teeth impression is taken from a suspect, a comparison can be made.
Bite marks have been divided into seven classifications:
Haemorrhage: A small bleeding spot.
Abrasion: Undamaging mark on the skin.
Contusion: Ruptured blood vessels, bruising.
Laceration: Punctured or torn skin.
Incision: Neat puncture of the skin.
Avulsion: Removal of the skin.
Artefact: Bitten off piece of body.
Bite marks may be found on the flesh of victims of a violent attack, particularly on the stomach, breasts or buttocks. Alternatively they may be found on the suspect, left by the victim during self-defence. The quality and accuracy of a bite mark are dependent on numerous factors, including time-dependent changes, where the bite mark was found, damage to soft tissue, dental similarity among individuals, and quality of photography, impressions or measurements. If a bite mark is only represented as a bruise, it is often extremely difficult to detect any individual characteristics.
In identifying human remains based in their teeth, dental records should ideally be obtained and compared to those of the unidentified body. If this is not possible, other clues in the teeth may be useful. Tooth eruption is linked to a certain extent with age, giving a possible rough estimation of the victim. When working with a young victim, the stage of development of a child’s teeth may be used to determine their age, though this can only be an estimate. The state and wear patterns of an individual’s teeth may give insight into the person’s age, diet, and dental history, as well as personal habits such as pipe-smoking and eating disorders.
A common method of comparing bite marks is to use transparent overlays to record the biting edges of a suspect’s teeth and compare them with the crime scene sample. These are often drawn on sheets of acetate, which can then be placed over one another for comparison. If it is possible, a dental cast will be made of the bite mark for later comparison to a suspect sample.
However the reliability of forensic odontology has been called into question on numerous occasions. The skin itself is not a good medium for dental impressions, often having a number of irregularities that will cause distortion. Bite marks can be altered through stretching, movement, or change in environment after the bite. There is also no set standard by which to analyse and compare bite marks.
Aside from criminal cases, forensic odontologists and dentists are greatly involved in the identification of victims of mass disasters. Dental records in particular are beneficial in identifying such victims.