Forensic odontologists may also work backwards matching the bite marks on objects found at a scene to a suspect. They develop the skill of comparing dental impressions taken from a person's mouth to bite-mark impressions on the skin (or possibly the bones) of a victim. There are many factors to consider, including matching for striations, whorls, indentations, pitting, and abrasions, and often this is done through computer-enhanced photography. They can also analyse bite marks on food in cases where a perpetrator might have taken a bite out of something in the victim's home and left it behind. An example is given below. What experts seek are a sufficient number of points of similarity between the evidence and a suspect to be able to say with a reasonable degree of certainty that this is the perpetrator.
However, bite marks left on foodstuff offer a three-dimensional impression, which is superior to the two-dimensional impression often left on skin. 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. Conversely bite marks might be dismissed as simple bruising. Some bites are forceful enough to leave a good impression, others are not.
The physical characteristics of both the bite mark wound and the suspect's teeth include:
- the distance from cuspid to cuspid
- the shape of the mouth arch
- the evidence of a tooth out of alignment
- teeth width and thickness, spacing between teeth
- the curves of biting edges
- unique dentistry
- wear patterns such as chips or grinding.
All of these are examined in detail and than compared, preferably in a blind test in which the odontologist is not aware of which teeth impressions belong to the suspect. At the very least, the injury pattern itself should be completely analysed first before looking at the data from the suspect.
Currently, there is no agreement among forensic odontologists about the individuality (uniqueness) of dentition or the behaviour of human skin during biting. Although these issues have never been proven scientifically, much research is currently underway in an attempt to prove the suspicion that each human dentition is unique. The sizes, shapes and pattern of the biting edges of the anterior teeth that are arranged in the upper and lower dental arcades are thought to be specific to that individual.
The amount and degree of detail recorded in the bitten surface may vary from case to case. And, even if it is assumed that the dentition is individual enough to warrant use in forensic contexts, it is not known if this individuality is recorded specifically enough in the injury. In situations where sufficient detail is available, it may be possible to identify the biter to the exclusion of all others. Perhaps more significantly, it is possible to exclude suspects that did not leave the bite mark.