Presentation Transcript

1. Bite mark analysis Lecture III 1- 36
2. Bite marks Bite-mark has a placeevidence in crime-scene analysis Cases shown on forensic TV shows reveal bite-mark evidence as conclusive and leading to identification of a perpetrator Bite-mark evidence and dental injuries are seen in abuse cases, involving children and also associated with elder abuse and violent crime(rage expression).
3. Bite marks cases The use of bite mark evidence began around 1870 with the Ohio vs. Robinson case. The case involved A.I. Robinson, a well-regarded member of his community, who was suspected of murdering his mistress.  There were five distinct bite marks located on the victim's arm which revealed five maxillary anterior teeth. Robinson happened to only have five maxillary anterior teeth, which Dr. Taft, a dentist, testified in court that Robinson’s dentition matched the bite marks from the victim.
4. Bite marks cases Another early case was Doyle v. State, which occurred in Texas in 1954. The bite mark in this case was on a piece of cheese found at the crime scene of a robbery. The defendant was later asked to bite another piece of cheese for comparison. A dentist evaluated the bite marks independently and concluded that the marks were made by the same set of teeth.
5. Bite marks In another case, there were only three suspects. The bites on the victim’s body indicated that the upper right first bicuspid of the biter was missing the buccal cusp. Two of the suspects had intact bicuspids, which left the third as the guilty party. After being confronted with this evidence, he confessed, and then was convicted and sentenced to prison.
6. Bite marks Cases Another landmark case was People v. Marx, which occurred in California in 1975. A woman was murdered by strangulation after being sexually assaulted. She was bitten several times on her nose. Walter Marx was identified as a suspect and dental impressions were made of his teeth. Impressions and photographs were also taken of the woman’s injured nose.
7. Bite marks Cases These samples along and casts were evaluated using a variety of techniques, including two-dimensional and three-dimensional comparisons, and acetate overlays. Three experts testified that the bite marks on the woman’s nose were indeed made by Marx and he was convicted of voluntary manslaughter.
8. Bite marks cases Few cases can conclusively be proven using bite-mark evidence alone, provided that the bite marks are well-recorded . In one case, a body with more than 100 bite marks was found. The bites were extensive and deep enough that most of the perpetrator’s tooth characteristics were well-recorded on the victim’s skin.
9. Bite mark analysis The bite mark analysis is stemmed from the fact that the human dentition is not identical from person to person.  A bite mark is known as the registration of the cutting edges of teeth on a substance caused by a jaw closing. Bite marks are as specific to a person as DNA or fingerprint analyses, similarly, No two individuals will have the exact same dentition in regards to shape, size and alignment of teeth.
10. Bite marks Human bite marks mark may be in the shape of a doughnut with characteristics recorded around the perimeter of the mark. The bite may be composed of two U-shaped arches that are separated at their bases by an open space.  Typically the diameter of the injury is from 25-40 mm.
11. well-recorded well-recorded
12. Bite marks Often the injury has a central area of bruising seen within the bite mark. This is caused by pressure from the teeth as they compress the tissue inward from the perimeter of the mark. It can also be determined from the type of bleeding beneath the skin whether the victim was alive or dead at the time the bite mark was delivered.
13. Bite marks Human bite marks on victims are most often found on soft tissue areas of all parts of the body. When a person is in defensive circumstances, such as when the arms are held up to ward off an attacker, the arms and hands are often bitten. On males the bite marks are commonly seen on the arms and shoulders.  Bite marks are often found on children who are abused. Bite marks can be altered through stretching, movement, or change in environment after the bite.
14. Bite marks Bites can occur on the flesh of a victims of a violent attack or the suspect. Teeth are used as weapon by the attacker. Alternatively they may be found on the suspect, left by the victim during self defense.
15. Bite marks When bite-mark evidence is associated with a crime, it is necessary to consider the bite might be from the victim. During the perimortem time (when an individual is dying), a victim may self-bite as a way to lessen the fear and pain associated with the assault.
16. Bite marks cases In Maplewood, Minnesota, there was such a case, which led the investigation was off track until the bite mark was analyzed. On the victim’s right wrist was a bite mark and the immediate assumption was that it was from the assailant. When her new boyfriend was arrested and impressions were made of his dentition, it was obvious that his arch width was far too great to have been the biter. At the morgue, impressions were made of the victim and it was determined that she had bitten herself during the assault.
17. Factors that may affect the accuracy of bite mark identification Factors related to dental profiles : The loss of teeth or the alteration of dental arch pattern is common in human populations. The onset of oral diseases such as dental caries has been shown to alter the arch and tooth configuration and must be taken into account when comparing a dental profile to the bite mark after a significant amount of time has passed since the mark was made.
18. The physical characteristics of both the bite mark wound and the suspect's teeth include: the shape of the mouth arch the curves of biting edges the distance from cuspid to cuspid teeth width and thickness, spacing between teeth wear patterns such as chips or grinding the evidence of a tooth out of alignment missing teeth unique dentistry procedures.
19. Bite mark analysis All of these are examined in detail and then compared, preferably in a blind test in which the odontologist is not aware of which teeth impressions belong to the suspect. The injury pattern itself should be completely analyzed first before looking at the data from the suspect.
20. How It's Done Experts first determine whether the bite is human or animal. They identify then the dental patterns by examining either a whole or partial set of teeth. Then record every detail about size, appearance, color, and location of the bite on the body, as well as the presence of other bites.
21. How it's Done Photographs involve using two rulers, one laid against the length and one against the width for size estimation. If rulers are not available, then something like a coin or matchbox is used for size comparisons Photographs are also taken without these items as well, to ensure that no one can say that evidence was hidden beneath them.
22. How It's Done Care is taken with the camera angle to make sure it is perpendicular to the bite mark. Photographs can then be enhanced with computer technology. Older techniques involved hand tracing on clear acetate.
23. Equipment used in photographing Properly scaled photographs are important to the legal process, as is the type of equipment used. Manually operated cameras with close focusing capability are best, with off-camera flash. The camera has to be rigidly supported, as with a tripod, because the details must be precisely recorded.
24. Equipment used in photographing Both color and black-and-white film is preferable to using only one or the other. Sometimes the bite-mark area has to be shaved to get a proper photo, and this has to be done with extreme care. When the wound is on a curved surface, photographs are made from several angles to capture the arch.
25. The direct method of bite mark analysis A dental model of the suspect’s teeth is compared to a life-size photograph of the actual bite mark. or The use of the “fingerprint powder lift” technique : It involves dusting the bitten skin with black fingerprint powder and using fingerprint tape to transfer the bite marks onto a sheet of acetate.
26. The direct method of bite mark analysis If the bite mark shows a good indentation rather than being smooth, an impression can be made. This is done right away before the skin changes, and a special frame is made to support it. If the impression is left on food, care is taken to prevent dehydration or rot.
27. Bite mark analysis A dental impression or mold is then made of the upper and lower set of teeth of the suspect. From this, the odontologist creates a transparency using free-hand tracing of the occlusal surfaces or uses computer imaging.
28. The indirect method of bite mark analysis The indirect methods involve the use of transparent overlays to record a suspect’s biting edges. Transparent overlays are made by free-hand tracing the occlusal surfaces of a dental model onto an acetate sheet. The use of transparent overlays is considered subjective (biased), easily manipulated and irreproducible.
29. The indirect method of bite mark analysis A photocopier-generated overlays is considered to be the best method in matching the correct bite mark to the correct set of models without the use of free-hand tracing (technique is sensitive, reliable, and inexpensive).
30. Digital close-up image of the bite edges of a suspect's teethplaced next to injury pattern seen in bite mark.
31. Computer generated outline of teeth placed ontodigital picture of a human bite mark.
32. Bite mark analysis Most bite mark analysis studies use pigskin, because it is histologically comparable to the skin of a human. the technique is using simulated pressures to create bite marks A G-clamp on an articulator is used to standardize the amount of pressure used to produce experimental bite marks instead of applying manual pressure to models on pigskin.
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34. Bite mark analysis Lecture IV 37-75
35. Factors that may affect the accuracy of bite mark identification time-dependent changes of the bite mark on living bodies damage on soft tissue where the bite mark was found Most bite marks demonstrate a “drag pattern,” as the person is likely moving in an attempt to prevent the injury. This further distorts tooth characteristics. Some similarities in dentition among individuals, as bite marks are not fingerprints.
36. Other Factors that may affect the accuracy of bite mark identification Poor photography, Poor impressions, as skin is not a good medium for dental impressions Poor measurement of dentition characteristics. For the bite mark to be accurately analyzed, the body must be examined in exactly the same position it was in when the bite occurred which can be a difficult if not an impossible task to accomplish.
37. Critics of bite mark comparison One particular case that highlighted the lack of uniqueness in bite marks involved two suspects (A&B) accused of attacking a man that had sustained a bite mark injury. Two separate forensic dentists, one representing the prosecution and one the defense, were brought in to analyze the mark. They reported conflicting results. One found the mark to come from suspect A and the other said it was from suspect B.
38. Critics of bite mark comparison This disagreement resulted from the fact that even though the two suspects had dental features making them unique, the bite mark itself was not detailed enough to condemn one of them. The vague outcome demonstrated in the case emphasizes the difficulty in proving uniqueness.
39. Bite marks Bite mark has limitations: Bite marks are not DNA and should be used cautiously when presented as crime-scene evidence. Bite marks can be used for inclusions or exclusion of the biter from a group of suspects, but rarely for a definitive conviction. To positively identify the biter individual tooth characteristics such as rotations, missing teeth, malformations, diastemas, and occlusal and incisal anatomy need to be present.
40. Bite mark uniqueness to make a positive identification The study of Rawson et al.suggested that if five teeth marks can be matched to five teeth, it can be said with confidence that only one person could have caused the bite, and if eight teeth were matched to marks this would be a conviction. However, there are a number of ways that the dental profile can be changed. For example, braces can be used to apply force to specific teeth, in order to shift the placement of multiple teeth. In an ideal situation, a bite mark should be swabbed for DNA while the victim is at the crime scene; this evidence could positively identify the biter.
41. Guidelines for bite mark analysis In 1984 the American Board of Forensic Odontology ( ABFO) established Guidelines for Bite Mark Analysis to enhance the quality of investigation and conclusions .
42. Bite marks In 1984, the ABFO began making an attempt to diminish the inconsistency and increase the power of bite mark analysis by creating bite mark methodology guidelines. The guidelines establish standards in describing bite marks and that reduces the risk of biased results. The ABFO also provides instructions on how to collect and preserve evidence.
43. Bite marks For example, they recommend that the collection of DNA evidence and detailed photographs of bites be taken together at the crime scene. The guidelines also outline what a forensic odontologist should record information such as the location, contours, shape, and size of a bite mark. They also provide a system of scoring to match a suspect’s dental profile and the bite mark.
44. Guidelines established for bite mark analyses by the American Board of Forensic Odontology (ABFO) Description of the bite marks Collection of dental evidence from the victim Collection of evidence from the suspect(s)
45. Description of bite marks Demographics Location of the bite mark Shape, color and size Type of injury
46. Description of bite marks Demographics This will include age, sex, race, name of the victim, examination date, referring agency, case number and name of the forensic dental examiner.
47. Description of bite marks Location of the bite mark The anatomical location of the mark, its surface contour (flat, curved or irregular), Tissue characteristics, Relative skin mobility.
48. Description of bite marks Shape, color and size The shape of the mark(round, ovoid, crescent or irregular), The horizontal and vertical measurements of the bite. Presence of an of injury in the bite mark Petechial hemorrhage, or ecchymosis Abrasion ,laceration or incision
49. Collection of evidence from victim Photography Saliva evidence Impressions Tissue samples
50. Collection of evidence from victim Photography Photographs are very important documentation especially in living victims since the tissue with bite mark cannot be excised. Close-up photographs should be taken. The scale must be positioned within the same plane as the bite mark. Resolution should be of high quality Accuracy of color balance assured Photographs are taken with no distortion In case of living victim, it is recommended to obtain serial photographs of the bite mark.
51. Collection of evidence from victim Photography Photographs of bite mark should be taken with a scale in place. Photographs without a scale in place is used to document that no injuries have been hidden by the scale. The ABFO No.2 reference ruler was developed by the American Board of Forensic Odontology for use in bite mark photography.
52. Collection of evidence from victim Photography The use of reflective ultraviolet(RU) photographic technique to enhance the image when the bite mark itself was not detailed enough. This technique identify concealed images of the teeth which remain after the bite mark has clinically disappeared. Reflective ultraviolet(RU) photography enhance the image by identifying photoactive melanin pigment in the injured tissue.
53. Collection of evidence from victim Saliva evidence Collection of saliva swabs from the surface of the bite injury. A cotton swab moistened in sterile saline is used. The bite mark is rubbed and the cotton is permitted to air-dry . The cotton swab is placed in a test tube and refrigerated A control sample is obtained from an area that is not associated with bite.
54. Collection of evidence from victim Saliva evidence Identification of organic ions such as thiocyanate and polymorphic enzymes such as alkaline phosphatase and amylase. Thiocyanate is 2.5 times higher in smokers than nonsmokers Identification of serological parameters including blood groups, serum polymorphic enzymes.
55. Collection of evidence from victim Impressions Impressions should be taken of the surface of the bite mark in dead or living individuals when there is sufficient surface detail to yield useful information. The material used must meet the American Dental Association specifications. The first impression should not be used, but kept in a safe place because it is a critical evidence that should not be exposed to any risks. Subsequent impressions should be numbered for future reference.
56. Collection of evidence from victim Impressions A small dam of wax or other material should be used to keep the impression material in the desired place. If the skin is hairy , it should be gently clipped. Shaving might cause other artifacts (remove scab or blood clot) Good impression material of low to medium viscosity should be used, whereas heavy body materials tend to distort the injured area due to pressure used to apply the material.
57. Collection of evidence from victimImpressions - cont. Premixed amounts of base and catalyst are injected directly onto the injured site with a syringe with a small orifice tip. The material is injected slowly to allow it to flow into the deep areas of the mark without creating bubbles in the impression. The setting time must be tested first Don't accelerate the setting time because it changes the properties of he material used. Materials that produce exothermic reaction must be used carefully in living individuals suffering burns. The heat generated might change the bite mark area in the deceased individual.
58. Collection of evidence from victimImpressions - cont. Some materials are used to support the thin impression material to prevent distortion: Orthopedic thermoplastic mesh material, Laboratory stone and acrylic impression tray material. Orthopedic thermoplastic mesh material: - It is a gauze-like material that should be softened in hot solution before being molded into place. - Another layer of impression is injected over the mesh to lock it in place, as it will bond to the first layer of impression material.
59. Collection of evidence from victimImpressions - cont. Laboratory stone: Dental stone can be used for backing, and staples can be used as a right angle mechanical locking of the stone to the impression material . Staples are placed into end of the impression away from the injury site.
60. Collection of evidence from victim Acrylic impression tray material: the material is mixed and molded to the approximate shape of the area of injury, using similar area on the opposite side of the body. For retention of the impression material, a tray adhesive is painted on the underside of the acrylic mold or holes are made. Before removal of the finished impression , the anatomical location, date, time, and initials of the dentist is written with a permanent pen.
61. Collection of evidence from victim Tissue samples: The dermis and underlying muscle and adipose tissue can be removed with wide margins in all directions for microscopic analysis. The specimen is placed immediately in a plastic bag, and can be kept in the freezer for a considerable length of time. There may be some changes due to the formation of ice crystals in the tissue .
62. Collection of evidence from suspect Before collecting evidence from the suspect, the odontologist should make certain that search warrant and legal consent has been obtained Evidence collection from the suspect includes: History. Photography. External examination. Intraoral examination Impressions. Study casts.
63. Collection of evidence from suspect 1- History History of any dental treatment subsequent to the date of bite mark. Medical history to document any medication the suspect has been taking at or before the date of bite. Saliva analysis with special techniques can detect the presence of some drugs.
64. Collection of evidence from suspect 2-Photography: Two extraoral photographs: Full face and profile. Five intraoral photographs: frontal view, two lateral views, occlusal view of each arch. Photograph of the maximum mouth opening with a scale in place.
65. Collection of evidence from suspect 3- External examination Factors that influence biting dynamics such as: Tempromandibular joint status Facial asymmetry Muscle tone and balance Measurement of maximal opening of the mouth Any deviation in opening and closing Any significant occlusal disharmony Any facial scars
66. Collection of evidence from suspect Intraoral examination: Saliva evidence if saliva swab has been taken from the victim (same laboratory specifications) Size and function of the tongue The periodontal condition ( mobility, area of inflammation or hypertrophy) Dental chart of teeth If anterior teeth are missing or badly broken down it should be determined how long these conditions have existed.
67. Collection of evidence from suspect 5- Impressions : Two impressions for the dental arches, using accepted impression technique and following the manufacturer’s instructions Record of the occlusal relationship. The impressions taken should be poured.
68. Collection of evidence from suspect 5- Impressions : Two impressions for the dental arches, using accepted impression technique and following the manufacturer’s instructions Record of the occlusal relationship. The impressions taken should be poured.
69. Collection of evidence from suspect 6- Study casts Any anatomical landmark on the master casts should not be altered by carving or trimming. Additional models are duplicated from master casts using accepted procedures.
70. Analysis of the evidence The forensic dentist first determines whether the pattern is truly a result of biting or whether it is an artifact. The bite mark pattern is then matched to the suspect’s dentition( for inclusion or exclusion). The dentist should use methods accepted in the courts which include computer images of bite mark and suspect teeth that have been enhanced and overlaid for matching.
71. Bites in other materials Criminals may leave their dental signature in bitten apple, chocolate, or cheese. Criminals may leave their bite mark on torn off section of an adhesive tape used to bind his victim. Food yields better information (good impression of the bite and less distortion). Swabs should be taken to detect salivary contamination ( DNA and serological parameters).
72. Nonhuman bites Animal bite is dependent on the dentition of the animal (scavenging dogs, cats and rats). The classic carnivore bite is characterized by 4 puncture wounds produced by large and aggressive canine.
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