In struggles between assailants and victims, there is a tendency for teeth to be used as a weapon. Sometimes it is the only defensive tactic for a victim to inflict serious injury on the assailant. It is a well known fact, that in sexual attacks including sexual homicide, rape and child sexual abuse, the assailants more often than not bite their victims. This can be viewed as an expression of dominance, rage and animalistic behavior. Not many people have the view that teeth can be such violent weapons (Sweet & Pretty, 2001).
Early recognition of bite marks is seen in old English Law where 'member proper for defense; including arms, legs and anterior teeth '. The first bite mark case in the United States was the famous Salem Witch Trials, in 1692. Rev. Burroughs who was persuaded and hungered used to bite his victims. During the trial his bite marks and of other people were compared to the victim's marks. The judges readily accepted the bite marks as evidence. In 1870, AI Robinson was suspected of murdering his mistress. Five bite marks were found on her arm. The bite mark evidence did not hold and Robinson was acquitted. Despite the negative outcome of the Robinson case, by 1890 bite mark evidence started to be recognized in scientific circles (Vale as cited Dorion, 2004).
Prior to 1950, the number of cases where bite marks were used as evidence was small when compared to today. A large proportion was reported in Europe and Japan, but most cases originated in the USA. In 2002, over 400 forensic odontologists were listed in the American Academy of Forensic Sciences (AAFS) (Dorion, 2004).
A major development in bite mark investigations in the USA began in 1962 when courses in forensic odontolgy began at the Armed Forces Institute of Pathology in Washington DC The development of forensic odontology was furthered by the publication of a book in 1966 by Gustafson, called 'Forensic Odontology'. This book had a substantial chapter devoted to bite marks and was the first major work to be published on this subject. Then in 1970, forensic odontology became a department in the AAFS, and became recognized as a specialty in forensic science. In 1976, the American Board of Forensic Odontology (ABFO) was organized. This was a step towards professionalism in the sector of forensic odontology. The ABFO started to provide a program of certification in forensic odontology. This furthered the science of forensic odontology and made it more reliable (Dorion, 2004).
A forensic dentist is not an ordinary dentist; s / he is a board- certified specialist who deals primarily with bite mark evidence. Although, one does not have to be a specialist to become an expert witness, it helps to strengthen the validity of the scientific evidence in court (O'Conner, 2006).
Forensic odontolgy is a branch of forensic medicine that in the interest of justice deals with dental evidence presented in the courts of law. The work of a forensic odontologist is to identify human remains through dental records, estimate age of both living and Deceased Persons, analysis of bite marks on victims and other substances such as foodstuffs and presentation of bite mark evidence in court as an expert witness (Sellar , 2002).
HUMAN BITE MARKS
Of all the components of the human body teeth outlast all other parts after death. Their durability makes it perfect for identification. Sometimes, they are the only means of identification left. A clear example is Adolf Hitler's dental records, which identified his corpse. It is claimed that no two people have identical teeth. Unlike fingerprints which remain unchanged, teeth become unique with wear and tear. For successful identification both ante and post mortem data should be available, even one tooth can be useful for identification (Evans, 2004).
There are about two hundred different tooth charting methods in the world, which provide an almost 100% reliable means of identification. The American approach, which is known as the universal system, gives a number to each of the thirty two adult teeth. Information is then recorded on each tooth according to the five visible surface of the tooth. With this information, the odontologists can complete a dental grid, unique to that person (Evans, 2004).
Human bite marks are found when teeth are used as weapons. They can be used as weapons of anger; weapons of excitement; weapons of control or weapons of destruction (Lotter, 2008). Bite marks are usually found on the skin of the victim. Females are usually bitten on the breasts and legs during sexual attacks, while men are usually bitten on the arms or shoulders and when in defensive postures bites can be found on the hands and arms (Sweet & Pretty, 2001).
The marks left by the teeth in a person may be used to identify an individual. Nowadays forensic odontologists have become reasonably skilled at identifying bite marks and relating it back to the person who has infected the mark (Horswell, 2004). A human bite mark is usually described as an elliptical or circular injury and the differences in size and shape of teeth can sometimes be easily noticed especially when teeth are missing or prominent (Lotter, 2008). However, a bite mark is not an overall accurate representation of the teeth; it also depends on the jaw movement and use of the tongue. The lower jaw is moveable and is the one that gives the most biting force, while the upper jaw is usually stationery and holds and stretches the skin (Evans, 2004). The most common type of bite marks are contentions. Incisions offer the best three dimensional images of the teeth. If avulsions and artefacts are combined, one can produce a three dimensional image too. There are seven types of bite marks; haemorrhage which is a small bleeding spot, abrasion which is an undamaging mark on skin, contusion which is a ruptured blood vessel bruise, laceration which is punctured or torn skin, avulsion were there is removal of the skin and artefact were a piece of the body is bitten off. These are then further divided into four degrees of impression, which when analyzed can help to note what kind of violence was executed and may be used as aggravating circumstances.
1. significant pressure
2. first degree pressure
3. violent pressure
4. skin violently torn from body
BITE MARK ANALYSIS
In odontology, for a physical comparison of a bite mark to be successful, the questioned evidence (Q) photograph of the bite mark must be accurately produced. It must then be recreated in a life size dimension, and is then called the Known (K) evidence. After this is done, the plaster cast of the defensive's teeth are used to identify any similarities in shape, positioning and so on and forth (Bowers & Johansen, 2004). The methods typically used include the older ones for example hand tracing the teeth perimeters on clear acetate, then Xeroxing the dental casts and then tracing them on acetate too. The dental cast teeth are then pushed into wax and filled thereafter with metallic powder. After this is done an x-ray film is used to capture the teeth impression. The direct superimposition of Q and K photographs are used when dentists testify in court, to show that there is sufficient identification value to reach a result. These are all meticulously made to scale to be able to provide consistent and accurate comparison results (Bowers & Johansen, 2004).
Recently, digital imaging software and image capture devices have created a more advanced and accurate way to avoid any discrepancies and allows the examiner to use the computer functions into a microscope for comparison. The computerized system of analysis bite marks has the benefits of creating accurate means of measuring physical parameters of crime scene evidence, corrects common photographic distortion and size discrepancies, helps to eliminate any examiner subjectivity, betters the control of image visualization, standardizes comparison procedures, helps to create reproducibility of results between separate examiners and is ideal for electronic transmission and archiving (Bowers & Johansen, 2004). The better the bite mark, the better an expert can make a reliable comparison (O 'Connor, 2006).
The American Board of Forensic Odontology (ABFO) follows bite mark standards and guidelines. The ABFO provides a list of generally accepted methods that meet the criteria of the scientific model. This is to help forensic odontology to achieve the objective of universally acceptable methodology. The ABFO provides guidance on how to preserve bite mark evidence, which is saliva swabs of bite site, photographic documentation of the bite site which includes lighting and scale, obtaining impressions of bite site including victim's dental impressions, tissue specimens. Guidelines are also formulated on the evidence collection of suspected dentition and these include the photographic documentation of the dentition, clinical examination with extraoral and intraoral considerations and dental impressions. In 1994 the ABFO indicated that the most widely used methods of comparing bite mark evidence were; the generation of overlays (acetate), test bite media such as wax exemplars, Styrofoam and so on and comparison techniques mostly using acetate.
All ABFO diplomats are expected to use the most analytical standards and methods suggested. Certain vital information must always be recorded and noted. These are done both in the case of a living victim as a Deceased individual. Demographics include details such as name of victim, case number and date of examination, person to contact, age of victim, sex and name of examiner. The location of bite mark, which includes the anatomical location, description of surface contour and whether it is flat, curved or irregular and a description of the tissue characteristics with details on the underlying bone, cartilage, muscle and fat structure and if the skin is fixed or mobile. The shape of the bite mark must be described for example if it is round, ovoid, crescent, irregular etc. The color of the bite mark is also important to note, eg red, purple.
The size is also to be noted, whether it is vertical or horizontal and preferably noted in the metric system. The injury can be a petechial hemorrhage, contusion, abrasion, laceration, incision, avulsion or artifact. Other information that is to be collected if possible is either the skin surface of indented or smooth (Bowers & Johansen, 2004). Since the skin is elastic, and depending on the victim some bite marks may last for hours while others may last for days. All bite marks alter themselves as time elapses, therefore it is important to photograph the bite marks as consistent intervals over a period of hours and days as recommended by the ABFO (O'Connor, 2006).
BITE MARKS AND CRIMINAL JUSTICE SYSTEM
The criminal justice system has long endorsed odontology as a major source of valuable aid. Apart from identifying perpetrators of crime, odontology has also assisted in the identification of unidentified persons (FBI Laboratory, 1989 as cited in Brennan, Gray-Ray, & Hensley, 1997).
Differences in teeth are as different as those marks found by other tools and fingerprints. Although a person's teeth may look the same, they are different in size, shape, arrangement, wear, damage, age, quality and quantity and habits of the individual (Levine, 1972 ac cited in Brennan, Gray-Ray, & Hensley, 1997 ). The FBI Laboratory in 1989 has concluded that dental uniqueness is beyond any reasonable doubt.
Bite mark analysis and evidence has been judiciously accepted in the United States since 1954 (Doyle vs. State). It was only in 1975, that bite mark evidence gave us the Marx standard of admissibility (People vs. Marx, 1975). The identification of a biter has been useful and instrumental in criminal investigations especially in cases of homicide; sexual abuse and child abuse cases (Pretty & Sweet, 2000 as cited in Bowers & Johansen, 2001). The USA has quite a developed system of dental records based on the Universal system and this helps considering especially in identifying 'John / Jane Doe' victims (O'Connor, 2006).
The Forensic weight and value of the bite mark is based on the characteristics of the bite marks that are similar to the defendant's. Most dentists' though, rely on a 'rule in' or 'rule out' fashion and therefore provide a weak linkage. So at this stage, the forensic weight of this evidence can be argued (Bowers & Johansen, 2004).
Forensic odontology is still new to criminal justice officials and its success in the criminal justice field has never been researched as yet. In the meanime two leading experts in the field, Dr. Haynes and Dr. West have been doing well by using ultra violet lighting to detect human bite marks on rape victims. With this method they have helped to capture and convict ten rapists. Bite marks in the investigation and prosecution of rapists is vital, since many rapists bite their victims. Bite mark evidence can be as conclusive as both DNA and fingerprint evidence in the case of rape. Valuable information can be obtained from the analysis of the bite mark. Odontology has proved to be exceptionally accurate in violent rape cases, since bite marks are mostly present in violent rape cases (Haynes and West, 1992 as quoted in Brennan, Gray-Ray, & Hensley, 1997).
It must be kept in mind that bite marks are not limited to skin. Teeth leave impressions on a number of things and if these are found at the crime scene they can help in the investigation, for eg a piece of chewing gum or food like cheese or chocolate (Geberth, 2006). As far back as 1906 in the UK, two burglars were convicted after one of them bit a piece of cheese which was found on the crime scene. The attorneys then showed that imprint exactly his front teeth (Evans, 2004).
The quality of the physical evidence, the variable nature of skin bruising and the insufficiency of scholars to accurately and scientifically prove that teeth are unique, create problems in the determination of positive identification to be used in court (Bowers, 2004). Legal challenges for bite mark evidence are usually two: relativity of analysis and whether it violates constitutional rights (Stimson & Mertz, 1997).
Although there are strong arguments that sustain that each human has a unique dental profile and is discernable in bite marks this has not been proved valid by any experiments and that causes serious problems when presenting bite mark evidence in the courts of justice. The amount and degree of detail of the bite mark may vary from case to case and if it is assumed that human dentition is unique it is sufficient to use as forensic evidence. In the case where it is not known whether this individual is specific, the most a bite mark can do is to exclude or include a person, as bite mark evidence is not sufficient to get a conviction (Bowers, 2004). More research is needed to prove beyond doubt that each human dentition is unique (Sweet & Pretty, 2001).
Other problems that are encountered with expert witnesses in court are that it is high that certainly their qualifications will ever be challenged on stand and most of the time odontologists work only on a part time basis with a law enforcement agency. Another issue is the problem if a standard protocol. In this particular field, specialists tend to use their own methods. There is also the digital divide, while others use the older methods (acetate). When comparing results this causes difficulties since the methods used are not the same and therefore blind reviews reflect poorly on the professionalism of odontologists (O'Connor, 2006).
FAMOUS BITEMARK EVIDENCE CASES
The most famous case where bite evidence led to a conviction is definitely the case of the serial killer Ted Bundy. Nowadays when referring to bite mark evidence, people still talk about the Bundy case. Bundy was never talked until the expert testimony of Dr. Sauviron secured a conviction and consequent execution. In the trial, photographic evidence of the bite marks and Bundy's teeth were shown. The acetate of the bite mark was then placed over the photo of Bundy's teeth leaving no doubt which teeth had left the impression.
Nobody is certain how many people Bundy killed between 1973 and 1978, but he was finally convicted for the murder of Lisa Levy of Florida. This was done because of the bites that were found on her body. Forensic bite mark analysis showed beyond doubt that the impressions were left by Bundy's irregular teeth (Lotter, 2008).
There were other cases were men were unfortunately convoked because of erroneous bite mark identification evidence. Ray Krone was jailed for ten years for a crime he had not committed. A waitress, in Phoenix was murdered in 1991 and Krone was sentenced for her murder. After DNA testing was done, Krone was free and the true perpetrator was identified. Forensic DNA was not available at the time of the prosecution and only a bite mark found on the victim's breast connected Krone to the murder. Even though the evidence was very weak, he was persuaded because of the bite mark a forensic odontologist had said matched the dentition of Krone. After an appeal, the tank top the victim was wearing was re examined and salvia was found that did not belong to Krone (Unknown Author, 2008). In 1992, Roy Brown was persuaded of stabbing, beating, biting and strangling a social worker in New York. The case rested on one piece of evidence, a bite mark. A local dentist tested that they matched Brown's teeth. He has been released in January 2007. DNA testing has proved that the saliva left in the bite mark did not match Brown's. Other inconsistencies were that Brown had two missing front teeth, but the expert tested that these could have been filled by twisting the skin (Santos, 2007).
Unfortunately there were cases were the prosecution used bite mark evidence to secure convictions, even if the person was innocent. With DNA and other evidence becoming more broadly available, most cases have been overturned where justice had not been served. Bite mark evidence must be used carefully and the over zealousness of candidates in acquiring a conviction must not interfere with evidence. In fact, in 1995 forensic odontologists have started to avoid using the term 'match' to eliminate errors, since other evidence should have produced together with bite marks (Santos, 2007). CSI effects on the general public has exaggerated the accurateness of bite mark evidence. Bite mark evidence can determine whether a subject can be excluded or whether the suspect could be the one who infected the bite. More research is needed since bite mark evidence on its own does not always produce comprehensive results.