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A bite mark left behind at the scene of a crime can be a highly effective way by which investigators can identify criminals.
It is a popular belief that the role of a forensic odontologist is to identify remains by their dental remains. This form of identification dates back as far as 66AD, the time of Nero, and has been used on Adolf Hitler, Eva Braun, the Waco Branch Davidien siege and numerous airline disasters.
In fact, criminal dental experts have many roles and one of these is to match bite mark impressions on victims, food, or other materials to the tooth structure of the suspect. Unlike analysis of dental remains, though, bite mark comparison is relatively recent dating back to the mid 70’s.
The most famous incident where bite mark evidence led to a conviction, was in the case of the notorious serial killer, Ted Bundy. Bundy who was responsible for an undetermined number of murders between 1973 and 1978 was finally tied to the murder of Lisa Levy through bites that he had inflicted on her body.
One of the officers at the scene of the crime had the forethought to place a yellow ruler next to the marks on the body which were then photographed.
Following Bundy’s arrest police obtained a search warrant allowing them to take a dental impression from Bundy and photograph his front upper and lower teeth and gums.
In the trial, the prosecution produced the photographic evidence of the bite marks and of Bundy’s teeth. They then proceeded to place an acetate overlay of the bite mark on the photo of the teeth.
This left no reasonable doubt that it was Bundy’s highly irregular teeth that left the impressions. On this evidence Bundy was convicted and sentenced to die in the electric chair.
THE EVIDENCE OF BITE MARKS
In the event of a suspected bite mark being found at a crime scene, a forensic odontologist is summoned and their first task is to obtain a saliva sample from the bite from which DNA analysis and blood typing can be undertaken later.
Next a linear scales, one for width and one for height, are placed near the mark and photographs are taken, color, black and white, and digital. On flat surfaces the phots are taken at a ninety-degree angle while on curved surfaces images are taken from varying angles. Video footage may also be used.
Following this, a variety of impressions, molds or casts are made particularly if the mark shows a good impression. These can be made from a variety of materials such as silicon rubber, plastic and powders.
In the case of human tissue the bite mark may then be excised for further analysis or the whole body may be taken to a facility where it may be examined using techniques such as scanning electron microscoipy and computer digitization.
With this type of information and with the benfit of computerized bite analysis software a highly detailed picture of the bite mark can be developed.
Once teeth impression are taken from a suspect these can be compared (in a blind test preferably) against the bite mark data and matched for upto seventy-six comparison factors.
These include whorls, indentations, chips, abrasions, striations, distances between cuspids, tooth width and thickness, alignment and mouth arch.
If, in the opinion of the forensic odontologist, the teeth match the bite mark, the evidence is then introduced in court, and usually involves the presentation of photography and transparent overlays, as in the Bundy case.
Bite marks left on human tissue may also be used to determine the time of attack and time of death as well as ways in which the body may have been moved.
While some bite mark evidence, such as in the case of Ricky Amolsch, in1994, has resulted in wrongful convictions, this field of forensic science has proved, on the whole, immensely useful to investigators.
In a remarkable case, the body of Karla Brown was exhumed in 1982, four years after having been buried. The impression that was lifted from the intact skin on her neck later led to a conviction.
Far more mundane was the burglar who left a piece of chewing gum, resplendent with a nice clear tooth marks, behind at the scene of the crime. Needless to say this genius got caught.
There are many cases, ranging from the bizarre to the ridiculous, where bite mark analysis has proved fruitful in the pursuit and incarceration of villains.
As technology advances further, this somewhat little noted field of forensic science will continue to gain greater and greater prominence.
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