Forensic Odontology: Bite Marks as Evidence in Criminal Case
Forensic odontology is a branch of dentistry that deals with the examination and analysis of dental evidence and analysis of bite marks created by the teeth on the victim’s body relating it to be presented as in the interest of justice. It also deals with the use of teeth and oral structures for identification in a legal context.
Various techniques involved in forensic odontology not only help with bite mark analysis it also deal with the identification of victim remains from terrorist attacks, arson cases, accidents, mass disasters, etc.
The principle basis in bite mark analysis and dental identification lies in the fact that no two oral cavities are alike and the teeth are unique to an individual hence the bite mark created by a set of teeth would also be different.
The dental evidence of the deceased recovered from the scene of crime/occurrence is compared with the antemortem records for identification.
Dental Formula is expressed as: The number of each type of teeth in the upper jaw / The number of teeth on one side of the lower jaw.
Dental Formula (permanent) = (2 incisors 1 canine 2 premolar 3 molar) / (2 incisors 1 canine 2 premolar 3 molar).
Dental Formula (temporary) = (2 incisors 1 canine 0 premolar 2 molar) / (2 incisors 1 canine 0 premolar 2 molar).
Forensic odontologists attempts to match bite marks found at the crime scene with the dental impressions taken from the suspect. Usually, crimes like sexual assaults hold bite marks to be common evidence. In these cases deep bite marks around the victim’s private area, neck, or sometimes even hand are common.
When the body is discovered at the crime scene, odontologists along with a medico-legal expert typically search for bite marks. Although bite mark evidence has been used across the world in many criminal prosecutions, there is no real scientific support or research into the accuracy or reliability of bite mark evidence.
Part of this is because victims of violent crimes can suffer multiple injuries, and what looks like a bite can be an unrelated injury. This is because, unlike a dental impression at a doctor’s office, bite marks are found on materials like skin, clothing, and soft tissue. Human skin is elastic; it swells, heals, and it can deform or warp a bite so that it does not align properly.
Furthermore, experts often use pictures to compare a person’s dentition to the bite mark on the victim, increasing the unreliability of bite mark evidence.
Another problem with bite mark evidence is its similarity to other “sciences” such as fingerprint analysis and firearm analysis: they are subjective to the person evaluating the evidence. Different experts have found widely different results when looking at the same bite mark evidence. Such subjectivity has no place being touted as science in the courtroom, as it is extremely persuasive to a jury, especially where someone has been wrongfully accused.
The process of comparing bite marks with a suspect’s dentition includes analysis and measurement of size, shape, and position of individual teeth in both the marks done carefully using measuring instruments and other techniques. Most of it includes the fabrication of overlays.
Some of the techniques involved in producing overlays include hand tracing from dental study casts, hand tracing from wax impressions, hand tracing from xerographic images, and the radiopaque wax impression method.
Other than these, bite marks from the crime scene could also be on some leftover food, or during an attack, the victim could bite the assailant as a part of self-defense, etc. In food, it could indicate the presence of an outsider who would have eaten half of the food, whichever might be during the crime. This could directly link the evidence to the culprit.
Collection of Bite Marks From Crime Scene
Collection of bite marks follows certain vital information in case of both living and deceased, some of them include Demographics(name, age, sex, race, date of examination of the victim and the name of the examiner), location of the bite mark- describing it anatomically is important, such as its contour, tissue characters, shape, and color. Recording the type of injury caused by the bite mark is important, sometimes the bite mark would have developed into abrasions or contours.
Photography of the bite mark is the most important and first step while collecting bite marks. This preserves the positioning and features of the raw bite mark before any alterations or changes have been made while transporting the victim or any substance on which bite marks are present. All the photographs should be taken with the camera at 90º (perpendicular) to the injury.
While taking swabs potential presence of salivary traces should not be overlooked and it should be collected in the presence of respective department specialists like a serologist. Swabs should be taken as soon as possible after the bite is inflicted and before the area is cleaned or washed. If it can be determined that the bite was inflicted through clothing, attempts should be made to seize the clothing for DNA analysis.
Bite mark analysis is relatively a new field and has been employed in certain cases in the United Nations and a few other countries. However, in India, it is an extremely rare field of interest and requires much more development.
Human dentition is influenced by genetic factors. It is said that a lot more paired DNA sequences are yet to be found among humans, bite marks are also dependent and could not be completely reliable because what a human can do at a cellular level or micro level is beyond imagination and is still a mystery to the world of science.