Bite-mark has a place evidence 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). Bite marks
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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
Robinsons dentition matched the bite marks from the victim.
Slide 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.
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Bite marks In another case, there were only three suspects. The
bites on the victims 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.
Slide 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 womans injured nose.
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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 womans nose were indeed made
by Marx and he was convicted of voluntary manslaughter.
Slide 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 perpetrators tooth characteristics were well-recorded on the
victims skin.
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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.
Slide 10
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. Bite marks
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well-recorded well-recorded w e l l - r e c o r d e d
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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.
Slide 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.
Slide 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.
Slide 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.
Slide 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 victims 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.
Slide 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.
Slide 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.
Slide 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.
Slide 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.
Slide 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.
Slide 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.
Slide 23
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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.
Slide 26
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.
Slide 27
The direct method of bite mark analysis A dental model of the
suspects 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.
Slide 28
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.
Slide 29
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.
Slide 30
The indirect method of bite mark analysis The indirect methods
involve the use of transparent overlays to record a suspects 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.
Slide 31
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).
Slide 32
Slide 33
Digital close-up image of the bite edges of a suspect's teeth
placed next to injury pattern seen in bite mark.
Slide 34
Computer generated outline of teeth placed onto digital picture
of a human bite mark.
Slide 35
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.
Slide 36
Thank You
Slide 37
Lecture IV 37-75
Slide 38
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.
Slide 39
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.
Slide 40
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.
Slide 41
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.
Slide 42
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.
Slide 43
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.
Slide 44
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.
Slide 45
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.
Slide 46
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 suspects dental profile and the bite
mark.
Slide 47
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)
Slide 48
Description of bite marks Demographics Location of the bite
mark Shape, color and size Type of injury
Slide 49
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.
Slide 50
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.
Slide 51
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
Slide 52
Collection of evidence from victim Photography Saliva evidence
Impressions Tissue samples
Slide 53
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.
Slide 54
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.
Slide 55
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.
Slide 56
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.
Slide 57
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.
Slide 58
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.
Slide 59
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.
Slide 60
Collection of evidence from victim Impressions - 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.
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Collection of evidence from victim Impressions - 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.
Slide 62
Collection of evidence from victim Impressions - 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.
Slide 63
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.
Slide 64
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.
Slide 65
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.
Slide 66
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.
Slide 67
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.
Slide 68
Collection of evidence from suspect 3 - External examination
Factors that influence biting dynamics such as: 1.Tempromandibular
joint status 2.Facial asymmetry 3.Muscle tone and balance
Measurement of maximal opening of the mouth Any deviation in
opening and closing Any significant occlusal disharmony Any facial
scars
Slide 69
Collection of evidence from suspect Intraoral examination:
1.Saliva evidence if saliva swab has been taken from the victim
(same laboratory specifications) 2.Size and function of the tongue
3.The periodontal condition ( mobility, area of inflammation or
hypertrophy) 4.Dental chart of teeth 5.If anterior teeth are
missing or badly broken down it should be determined how long these
conditions have existed.
Slide 70
Collection of evidence from suspect 5 - Impressions : 1.Two
impressions for the dental arches, using accepted impression
technique and following the manufacturers instructions 2.Record of
the occlusal relationship. 3.The impressions taken should be
poured.
Slide 71
Collection of evidence from suspect 5 - Impressions : 1.Two
impressions for the dental arches, using accepted impression
technique and following the manufacturers instructions 2.Record of
the occlusal relationship. 3.The impressions taken should be
poured.
Slide 72
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.
Slide 73
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 suspects
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.
Slide 74
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).
Slide 75
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.