Bite-mark Evidence

When a bite-mark is left behind during the commission of a crime it is called bite-mark evidence.  The bite-mark may be left in food, an inanimate object, or on a human being.   Bite-mark evidence has been used many times in the past in court cases; one of the most famous cases involving bite-mark evidence involved the trial of Ted Bundy.  Ted Bundy’s teeth were compared to bite-marks left on one of his victims and a positive ID was made from the bite-mark to Bundy.

The big question today is how reliable bite-mark evidence is.  Bite-mark evidence has been used to convict a number of people, but has, with the advent of DNA, been proven to do so wrongly in a number of cases.  Many cases have surfaced in which people have been convicted of a crime using bite mark evidence and have been exonerated, unfortunately years later, using DNA.  In fact, a 1999 study found a 63% rate of false identification using bite-mark evidence.

Bite-mark analysis works much like shoe impression or fingerprint analysis, both class and individual characters are examined in order to make a positive ID.  The class characteristics for bite-marks, which narrow down evidence as belonging to a small group, include size, shape, and bite of the teeth. Individualizing characteristics of bite-marks, accidental traits that make the bite-mark impression unique to one person, include fractures, wear, and congenital malformations of teeth as left behind in the bite-mark impression.  So why is bite-mark evidence proving to be so unreliable?

Bite-mark evidence is mainly at issue when it involves the human skin.  Most of the problems come from some of the basic characteristics of skin.  Skin shifts when it is bitten, skin also stretches in different ways when a person is in different positions, so if the victim was moving and the skin was shifting during the bite incident how accurate of a pattern can the bite-mark leave behind for comparison?  Another factor that can influence the bite-mark and its examination is time.  One must consider how much time elapsed between the infliction of the bite-mark and when it is to be examined for comparison.   The natural healing and bruising process changes the skin and the wound over time, changing the pattern as it heals.

Given these uncertainties, many agree that bite-mark evidence, particularly on skin, is mainly helpful in excluding suspects but should not be used as an individualizing tool.   Everyone one agrees that the most important tool for examining a bite-mark is a DNA test. The saliva from a bite-mark, more than anything else, can be used to make a positive match to a suspect.