Open Access Research Article
RELIABILITY AND VALIDITY OF BITE MARK ANALYSIS: CRITICAL EXAMINATION AND IMPROVEMENT OF CURRENT PRACTICES
Published Paper
Article Details
AUTHORED BY - SAHANA ASHOKUMAR
(B.COM (MM), LL.B (HONS), LLM
BITE MARK ANALYSIS:
Bite
mark analysis is a forensic practise/procedure in which the bite marks on the
victim’s skin are compared to the alleged biter’s teeth. The purpose of bite
mark analysis is to identify the biter with a reasonable degree of care and
certainty. Bitemark analysis is a process that includes examining patterned
injuries found at a crime scene, determining them to be bitemarks, and then
comparing these marks with dental impressions from a person of interest (POI).
This analysis relies on three main components:
1. The front
teeth of the presumed biter (POI’s anterior dentition),
2. Accurately
transferring the biter’s dental features onto a surface (like human skin) to
create a bitemark, and
3. Conducting
image analysis on the alleged bitemark to reveal the dental pattern, compare it
with the dental features of the person of interest, and interpret the findings.
v The
accuracy of bite mark analysis has been strongly disputed, and it is a
specialist discipline that necessitates substantial training and experience.
v The current
condition of the bite mark, the investigator’s expertise, and the availability
of bite marks with similar characteristics are only a few of the variables that
might determine how accurate a bite mark analysis is.
v Bite mark
analysis can be a useful tool in forensic investigations despite its
difficulties.
Stages of Bite
Mark Analysis:
The first stage of bite
mark analysis involves confirming if the injury is indeed a bite mark and
assessing its forensic significance.
1. Demographics:
(a)
Includes
victim’s name, case number, date of examination, referring agency, contact
person, age, race, and sex of the victim, and examiner’s name.
2. Location of Bite Marks:
(a)
Non-sexual
bite marks can be found on arms, legs, fingers, hands, chest, and ears.
(b)
Sexual
bite marks may be present on breasts, neck, thighs, genitalia, axilla, buttock,
upper back, arms, cheeks, etc.
(c)
Frequencies
of occurrence: breast, arm, genitalia, back, thigh, legs, nipple, hand,
buttock, abdomen, waist, face, neck, etc.
3. Shape, Size, and Arrangement of Teeth:
(a)
Bite
marks can be crescent, ovoid, round, or irregular in shape.
(b)
Human
incisors produce rectangular marks, while canines yield triangular marks.
(c)
Vertical
and horizontal dimensions of the bite mark are measured.
(d)
Comparison
of prominent dental features like tooth size, arrangement, and secondary
features like gaps or broken teeth.
(e)
Both
prominent and secondary dental features must match for a bite mark to be
considered a match.
(f)
Note
tooth numbers, missing teeth, and placement of tooth marks.
4. Size of Dental Arch:
(a)
The
size relationship of bite marks based on dental arches can indicate if it is a
child or adult bite.
(b)
Adult
arches’ average diameter from canine to canine is 25-40mm.
5. Suction Marks:
(a)
Suction
marks or hickeys are collections of punctate haemorrhages, resembling a ‘sun-burst.’
(b)
Usually
found after sexually oriented crimes due to suction or negative pressure
leading to blood leakage from capillaries.
6. Type of Injury:
(a)
Bite
marks can cause petechial haemorrhages, contusions (ruptured blood vessels),
abrasions (undamaging marks), avulsions (torn skin), lacerations (near puncture
of skin), incisions (neat punctured or torn skin), and artifacts (bitten off
piece of body).
(b)
They
can be classified into four degrees of impression: clearly defined, obviously
defined, quite noticeable, and lacerated.
7. Colour of the Wound:
(a)
The
colour of the bite mark, e.g., red, purple, etc., should be noted during
examination.
8. Evaluation of Bite Mark Photographs:
(a)
High-resolution
images are essential for examination, allowing amplification to life-sized
dimensions without pixilation.
Availability
and Implementation in India:
(a) The
implementation of advanced bite mark analysis techniques, such as digital
methods and computerized programs, may vary in different regions of India.
(b) Some
forensic facilities and institutes in India may have access to these
technologies, but the extent of their usage may differ based on resources and
expertise.
(c) As technology
advances, it is likely that more forensic institutions in India will adopt
these digital methods for bite mark analysis to enhance accuracy and efficiency
in criminal investigations and legal proceedings.
Comparison
Techniques in Bite Mark Analysis:
A. Direct Comparison Technique: Cast on
Photo Method In the direct method or cast on photo method, a straightforward
comparison is made between photographs and models or a fingerprint powder lift
model. This technique allows investigators to place models from the suspect
directly over a life-sized photograph of the bite mark for clear demonstration.
The finger print powder lift technique involves dusting the bitten skin with
appropriate powder and a brush, then using fingerprint tape to transfer the
marks onto a sheet of acetate. Caution is advised during the development of the
print to avoid any damage.
B. Indirect Method-Overlay: Utilizing
Transparent Overlays The indirect method involves the creation of transparent
overlays to record the suspect’s biting edges. This process entails free-hand
tracing the occlusal or incisal surfaces of a dental model onto an acetate
sheet, which is then placed over scaled 1:1 photographs for comparison.
However, the use of transparent overlays is considered subjective, easily manipulable,
and irreproducible. An alternative to free-hand tracing is the use of
photocopier-generated overlays, which provide a more reliable means of matching
the correct bite mark to the appropriate set of models. The four methods of
bite mark overlay production are:
1. Computer-based
2. Radiopaque
wax method
3. Xerographic
4. Hand-traced
Additional Special Methods for Bite Mark Analysis:
a. Stereometric Graphic Analysis: This
technique involves analysing bite mark patterns using a stereometric approach,
providing three-dimensional insight into the marks.
b. Vectron: Vectron is a specialized tool that
aids in bite mark comparison, helping investigators analyse and interpret complex
bite patterns.
c. Scanning Electron Microscopic Analysis: Utilizing
advanced microscopic technology, this method allows for high-resolution
examination of bite marks, revealing intricate details.
d. Image Perception Technology: This
innovative approach involves the use of advanced software and algorithms to
enhance image analysis and bite mark comparisons.
e. Experimental Marks: Researchers may conduct
controlled experiments to better understand and interpret bite marks,
contributing valuable insights to the field of bite mark analysis.
Factors
Influencing Severity of Bite Marks:
The severity of bite marks is
influenced by the force with which the biting teeth and tongue inflict the
injury. The negative pressure created during the biting process can lead to extra-vascular
bleeding, resulting in bruising at the centre of the bite mark injury. As the
injury undergoes a healing process in the living person’s skin, these bruises
may exhibit colour changes over time. There are four degrees of impression that
can be examined to detect the type of violence involved:
a. Significant
pressure
b. First-degree
pressure
c. Violent
pressure
d. Skin
violently torn from the body.
CLASSIFICATION OF BITE
MARKS:
Several classification systems have been
suggested for categorizing bite marks:
1. Cameron and Sim’s Classification: This
classification is based on the type of agent responsible for the bite marks and
the material on which the bite mark is found. The agents can be human or
animal, and the materials can include skin, body surfaces, food items, or other
materials.
2. MacDonald’s Classification: This
classification is widely used and focuses on the cause of the bite marks. It is
an etiological classification that identifies three types of bite marks: a.
Tooth Pressure Marks: These marks are produced when teeth directly apply
pressure to tissues. Typically, incisal or occlusal surfaces of teeth cause
these marks. b. Tongue Pressure Marks: These marks occur when the tongue
presses tissue against rigid areas like the lingual surface of teeth or the
palatal surface. These marks are sometimes referred to as “suckling” marks and
often involve a combination of sucking and tongue thrusting. c. Tooth Scrape
Marks: These marks result from the scraping of teeth across the bitten material.
Usually caused by anterior teeth, they appear as scratches or superficial
abrasions.
3. Webster’s Classification: This
classification categorizes bite marks based on the depth of tooth penetration
into the foodstuff.
a) Type 1: Food items that fracture easily
with limited tooth penetration, such as hard chocolate.
b) Type 2: Bite marks on food items where
fragments break off, and teeth penetrate considerably, like marks on fruits.
c) Type 3: Bite marks showing complete
penetration on food items with slide marks, such as cheese.
These
classifications aid in the analysis and understanding of bite marks, providing
valuable information in forensic investigations and criminal cases.
COLLECTION OF EVIDENCE IN BITE MARK ANALYSIS:
Collection
of Evidence from the Victim:
v DNA from
salivary trace evidence is obtained by swabbing the bite site using the double
swab technique.
v Photography
is a crucial element of dental forensic examination to document maxillary and
mandibular teeth, pathologies, and dental treatment.
v Close-up
photographs of bite marks are taken under high resolution with colour balance
maintained for accurate representation.
v The use of
a scale and proper camera orientation helps minimize distortion during
photography.
v Photographic
evidence is commonly used for recording skin bite marks, but postural effects
and secondary distortion should be managed.
Collection of Evidence from the Suspect:
v Extra oral
examination includes assessing hard and soft tissues, TMJ status, facial
asymmetry, and muscle zones.
v Intra oral
examination includes examining salivary evidence, tongue size and function, and
dental conditions.
v Dental
casts are obtained with ADA specified material to create a master cast for
further examination.
Analysis and identification of bite marks:
v Forensic
science uses individual traits and characteristics of the teeth and jaws to
identify the perpetrator of a bite mark.
v Recognition
of a patterned injury as a human bite mark is followed by pattern analysis to
provide information about the suspect or offender involved in the crime.
v Specific
teeth marks and characteristics are used for comparisons with the suspects’
teeth to determine the origin of the bite mark.
Physical Comparisons:
v Various
methods are used to physically compare suspect dentition and physical bite mark
injuries, including scanning electron microscopes, overlays, impressions, and
3D laser scanning of dental casts.
v Computer-generated
overlays have a high degree of specificity and accuracy, but they are not
widely used among forensic odontologists.
v Biological
techniques focus on salivary DNA recovery and the use of bacterial fingerprints
for suspect identification.
v Uniqueness
of The Human Dentition:
v The human
dentition is unique, and occlusal profiles differ among individuals, allowing
for the creation of a dental occlusal profile database.
v However,
dental occlusal profiles are not constant throughout life and may require
routine updates for accurate use in forensic analysis.
Bitemark Severity Index:
v The
bitemark severity index is a scale from 1 to 6 used to measure the severity of
bite marks.
v The index
should be easy to use, reproducible, applicable to both the living and the
dead, and allow for future statistical analysis.
v The index
is used to assess the forensic significance of bite marks, with 3 and 4 having
the highest forensic significance.
v Proper
education for crime scene police officers is essential for the effective use of
the bitemark severity index in bite mark analysis.
DENTIST AS AN EXPERT
WITNESS:
First use of dental evidence in court:
In 1814, in[1]
Scotland, the use of a dentist as an expert witness was documented in the case of Mrs. Janet McAlister. Dr. Granville Sheep
Pattison, a lecturer of anatomy, and two students were charged in the
high court in Edinburgh for violating Mrs. McAlister’s grave. Dental evidence
played a crucial role in the case, as a maxillary denture was discovered in the
dissecting room, near the college where they had moved her body after burial.
Dr. James Alexander, Mrs. Alister’s dentist, testified as a witness for the
prosecution. He confirmed that a set of dentures found matched only one of the
heads in the dissection room.
In 1831, a
woman named Caroline Walsh disappeared after moving in with an Irish
married couple. A woman later found on the streets in a destitute condition was
claimed to be Caroline Walsh. However, it was revealed during the trial that
this woman had lost her front teeth many years ago, whereas the real Caroline Walsh
had perfect teeth. Although Mrs. Walsh was never found, the accused was still
convicted based on the dental evidence presented in the case[2].
The first
documented use of dental evidence in court in India was in 1193 AD. During this
time, in the case of Jai Chand, the Raja of Kanauji, who
was murdered after his kingdom was destroyed by Muhammad’s army, he was
identified by his false teeth. This historical case marked the earliest
recorded instance of dental identification being utilized as evidence in the
Indian judicial system.
In the
fascinating evolution of forensic dentistry, dentists have played a crucial
role in providing expert testimony in court cases, helping to identify
individuals and solve mysteries that would otherwise remain unsolved. Some historical
cases that showcase the early use of dental evidence in legal proceedings are:
a) One
notable case occurred in the United States during the 19th century. Dr.George Parkman, a respected
professor at Harvard University, vanished on November 23rd, 1849. Among the
suspects was John White Webster, owing money to Dr. Parkman. Upon searching
Webster’s laboratory, human remains were discovered. To ascertain the identity,
Dr. Parkman’s dentist, Dr. Nathen Cooley Keep, was called upon. Three years
earlier, Dr. Keep had crafted upper and lower dentures for Dr. Parkman, and he
used these dentures to positively identify the body. Dr. Keep’s expert
testimony proved instrumental in convicting Webster, marking the first recorded
instance of a dentist testifying in a U.S. court[3].
b) Another
intriguing case involved William the
Conqueror, who fell
from his horse and died at the age of forty-four. Centuries later, in 1868,
when his tomb was opened, the remains were found to be remarkably
well-preserved. Forensic dentists utilized the remarkable durability and
longevity of teeth, even in severely damaged or long-buried bodies, to confirm
the identity of the historical figure[4].
c) In 1870,
the use of bite marks as evidence was explored in a trial where Mr.A.I.Robinson was accused of
murdering his mistress. The comparison of bite marks from Mr. Robinson’s five
maxillary teeth to the suspect’s bite marks led to identification, but he was
not found guilty[5].
d) Another
intriguing case from 1873 involved a body found in the ashes of a burned
cottage in Maryland. Mrs. Winfield S.
Gross was suspected of murdering her husband for insurance money.
The body was examined at the Baltimore College of Dental Surgery, and Dr. F. J.
S. Gorgas provided a detailed description of the jaws and remaining teeth. The
forensic dentist concluded that the remains did not belong to Mrs. Gross,
ultimately leading to the arrest of Mr. Udderzook, Mrs. Gross’s brother-in-law,
who was found in possession of the victim’s belongings.
e) In yet
another historical event, following the assassination of President Abraham Lincoln in 1865, rumours circulated that the
assassin, John Wilkes Booth, was still alive. In 1893, the body believed to be
Booth’s was disinterred and examined. The family dentist played a pivotal role
in identifying Booth’s body based on peculiar jaw formation documented in
dental records during a dental visit for filling restoration[6].
f) After
World War II, there were widespread rumours suggesting that Adolf Hitler had managed to escape
with his wife, Eva Braun. However, historical evidence has proven that both
indeed died together in 1945. Their bodies were burned and buried by Russian
soldiers, making it challenging to refute the rumours due to the lack of
pre-death and post-death records. Eventually, a breakthrough came when remnants
of a bridge were found among the pieces of Hitler’s jaw. The bridge’s unique
reconstruction and signs of periodontal diseases provided vital clues for
identification. In this critical process of dispelling the rumours, the work of
Hitler’s dentist, Hugo Blaschke, became crucial. By comparing the dental work
recorded by Blaschke with that of Hitler’s dental records, the authenticity of
Hitler’s death was confirmed, putting an end to the speculations surrounding
his fate[7].
These
early cases highlight the significant contributions of dentists as expert
witnesses in courtrooms, using their expertise to unravel mysteries, identify
individuals, and bring justice to the victims. The history of forensic
dentistry exemplifies the intersection of science, law, and human curiosity in
unravelling the truth behind some of history’s most fascinating cases.
FACTORS CONTRIBUTING TO UNRELIABILITY FOR BITE MARKS ANALYSIS:
There are
several factors that contribute to the unreliability of bite mark analysis.
A. First,
human skin is not a reliable surface to analyse because it changes over time
depending on swelling, healing, and skin elasticity.
B. Second,
bite marks can be distorted by the force of the bite, the position of the
victim’s body, and the clothing that the victim is wearing.
C. Third,
there is no standardized method for collecting and preserving bite mark
evidence.
REVIEW REPORTS ON BITE MARK
ANALYSIS:
In recent years, there have been several
calls for reform in the practice of bite mark analysis. In a 2009 report, the
National Academies of Sciences, Engineering, and Medicine urged greater
investigation into the validity and reliability[8].
According to the draft review, the scientific
basis of forensic bitemark analysis is insufficient due to the lack of support
for its three key premises.
i.
Firstly, there is no evidence to suggest that human
anterior dental patterns are uniquely specific to individuals.
ii.
Secondly, the consistent transfer of these patterns to
human skin has not been established.
iii.
Lastly, the accuracy of analysing defining
characteristics of bitemarks to include or exclude individuals as their source
has not been demonstrated.
The report
also called for the development of standardized methods for collecting and
preserving bite mark evidence[9].
The draft review highlights three key unsupported premises in forensic bitemark
analysis.
1. Firstly,
there is no evidence to prove the uniqueness of dental patterns formed by a
person’s front-most biting teeth. No population studies have been conducted to
determine the prevalence of such distinguishing features.
2. Secondly,
the accuracy of transferring these dental patterns to human skin is questionable.
Bitemarks can be distorted by skin elasticity, victim movement during the
biting, and subsequent swelling or healing, making it challenging to reflect
the true dental characteristics of the biter.
3. Lastly, the
ability of bitemark examiners to accurately analyse skin injuries is uncertain.
Previous studies, including one from 2016, demonstrated inconsistencies among
practitioners in identifying bitemarks and determining their source, be it
adults, children, or animals.
A draft
evaluation of the scientific underpinnings of bite mark analysis was published
by the National Institute of Standards and Technology (NIST) in 2022[10]. The NIST
review found that bite mark analysis lacks a sufficient scientific foundation.
The review also found that there is no evidence that bite mark analysis can be
used to identify a biter with a reasonable degree of certainty[11].The NIST review
has been met with mixed reactions. Some experts have argued that the review is
too critical of bite mark analysis, while others have argued that the review is
justified. Despite the controversy, there is a growing consensus that the
practice of bite mark analysis needs to be reformed. In order to improve the
reliability and validity of bite mark analysis, there is a need for more
research, the development of standardized methods, and the education of
forensic dentists.
The
American Board of Forensic Odontologists (ABFO) revised its guidelines in 2018
for collecting and assessing bitemark data from victims and potential biters. The
evaluation process involves the following steps:
1.
Determining if the pattern is indeed a bitemark by
taking photographs of the mark, identifying arches and midline, and checking if
individual teeth marks are distinguishable and comparable to normal human
variation.
2.
Interpreting and analysing bitemark features,
including locating the pattern, noting size, shape, and anomalies, and
collecting evidence for further assessment.
3.
Comparing the bitemark data to the dentitions of
Persons of Interest (POIs) and non-POIs using various methods like overlays,
test bites, and additional techniques such as transillumination or scanning
electron microscopy.
4.
Forming conclusions with levels of certainty:
whether the subject and non-POI dentitions can be excluded, not excluded, or
remain inconclusive as the cause of the bitemark pattern. The ABFO does not
endorse terms indicating an absolute match to a specific dentition.
It is important to note that the ABFO’s language in
the 2018 document reflects a sense of uncertainty in their conclusions, using
terms like “excluded,” “not excluded,” or “inconclusive.” The document does not
endorse a definitive link between a specific dentition and a particular
bitemark.
APPLICATIONS IN
MEDICO-LEGAL CONTEXT:
Forensic
Dentistry takes a diversified approach and specific expertise to be
effective in both criminal and civil cases, it includes the inspection,
analysis, and presentation of dental evidence, assisting in the detection and
prosecution processes[12].
The identification of deceased individuals using an inclusive range of
techniques, such as those employed by forensic dentists, is fundamental which
includes the analysis of periodontal tissues[13],
analysis of bite marks on human tissues[14],
assessment of anatomical structures[15],
and anthropological studies[16].
Law enforcement
officials, forensic pathologists, forensic odontologists, forensic
anthropologists, serologists, participants, and other parties must collaborate
in a collaborative way while carrying out a forensic identification. Every
individual on the team offers their own knowledge and perspective to the
investigation and legal proceedings. The accuracy, reliability, and
exhaustiveness of forensic identifications are guaranteed by this collaborative
method.
In
medico-legal applications, forensic dentistry is essential for assisting to
identify an individual when employing more conventional methods of
identification is challenging or impractical. Dental evidence, including bite
marks, dental anomalies, restorations, and dental records, can offer crucial
information that confirms or contradicts witness testimony and aid in
identifying suspects or victims. Forensic dentists are instructed to carefully
examine dental evidence, make comparisons, and clearly and impartially explain
their conclusions within the bounds of the law.
EVIDENTIARY VALUE OF HUMAN
BITEMARKS:
1.
General
Considerations:
v Once a
pattern is identified as a human bitemark, its forensic significance or
evidentiary value should be evaluated before comparing it to dentitions.
v Induced
skin distortion and other factors related to human skin nature can impact the
recording of dental features, arch size, and shape in the bitemark.
v Various
factors influence the interpretation of bitemarks on human skin.
2.
Criteria
for Determining Evidentiary Value:
Conditions
and features of bitemark evidence that indicate sufficient evidentiary value
for comparisons to dentitions include, but are not limited to:
v Adequate
and properly focused photographs of the bitemark with and without a reference
scale.
v Properly
illuminated and exposed images made with the image receptor parallel or
correctable for the angle theta (?) using image-management software.
v Locatable
maxillary and mandibular arches with determinable midlines.
v Visible
marks caused by individual teeth, recognizable based on class characteristics
and relative location.
COLLECTION OF EVIDENCE:
The
process of collecting evidence in bite mark analysis involves the following
steps:
Collection of bitemark evidence
from the bite victim[17]:
1. Documentation: A written record detailing the
location, appearance, colour, size, and orientation of the bite mark.
2. Photography: Comprehensive photography
capturing various angles, with and without ABFO No. 2 scale, in colour and
black and white, using on and off-camera flash, and UV photography. Close-ups
are taken at a 1:1 scale, and multiple body positions are photographed to
assess the impact of movement.
3. Salivary swab: The deposition of saliva during
the biting process is inevitable. A double-swab technique is recommended for
recovery. Swabs are taken from the bitten surface using moistened cotton wool
followed by a second dry swab. Control swabs are also taken from the victim for
comparison.
4. Impression of the bite injury: Impression
materials such as vinyl polysiloxane are used to capture irregularities
produced by the teeth, such as cuts and abrasions on the bitten surface. These
impressions are then cast in plaster to create a lasting record of the injury.
EVIDENCE COLLECTION FROM THE BITE SUSPECT:
1. History and Dental Records: Dental
records obtained from the suspect’s dentist play a crucial role in establishing
the identity of the suspect.
2. Photographs: Both intraoral and extraoral
photographs of the suspect are taken. Extraoral photographs include profile and
full-face views, while intraoral photographs cover frontal, lateral, and
occlusal views of both dental arches.
3. Impressions and Study Casts: Impression
taking and fabricating study casts of the suspect’s dentition are important for
the examination of bite marks.
4. Test Bites: Test bites are performed to
investigate the position, shape, and alignment of the suspect’s incisal edges
using materials like baseplate wax, aluwax, coprwax, and silicone.
5. DNA Samples: Non-invasive procedures like
saliva extraction or invasive procedures using the suspect’s whole blood are
performed to collect DNA samples for comparison with biological evidence found
at the crime scene.
BITEMARKS MADE BY DIFFERENT
DENTITIONS:
Distinguishing
bitemarks made by adult teeth from those made by children’s teeth should
consider not only size but also class characteristic differences between
permanent and primary dentitions. Bitemarks made during the mixed dentition
phase may exhibit characteristics of both permanent and primary dentitions[18].
Here are
some specific ways to improve the practice of bite mark analysis:
v Conduct
more research on the reliability and validity of bite mark analysis.
v Develop
standardized methods for collecting and preserving bite mark evidence.
v Educate
forensic dentists about the limitations of bite mark analysis.
v Use bite
mark evidence in conjunction with other forensic evidence, such as DNA
evidence.
In the case
of State v. Green[19], it
was highlighted that the dental expert must be aware of the scale displayed in
the picture for accurate analysis. Therefore, it is crucial to include a
measurement method like a ruler or tape measure in the photographs of the bite
mark and the defendant’s teeth[20].
Additionally, a plaster cast of the defendant’s dental impressions can be
utilized to create a plastic overlay, aiding in the marking of contact points,
and forming a representation of the defendant’s bite marks or the cutting edges
of their teeth[21].
There is a significant issue at
present regarding the improper use and misinterpretation of bite mark evidence
in the field of forensic odontology. The scrutiny of forensic evidence in
criminal cases, has reached unprecedented levels of legal and scientific
examination. Certain subfields of forensic science, particularly those
involving pattern-matching, have recently been acknowledged as having weak
foundations and making exaggerated claims, casting doubt on their admissibility
as evidence in court. Some of these forensic testimonies had been accepted for
decades without raising any judicial concerns. The most significant and
official criticism of these flaws was made in the 2009 report by the National
Academy of Sciences’ Committee on Identifying the Needs of the Forensic Science
Community[22].
A report in 2022 from the
National Institute of Standards and Technology (NIST) is titled “Critical
Examination and Improvement of Current Practices.”[23].
The report provides a critical examination of the scientific foundation of
bitemark analysis and identifies areas where research is needed to improve the reliability
and validity of the discipline. The report finds that there is no scientific
consensus on the three key premises of bitemark analysis:
1.
That
human anterior dental patterns are unique at the individual level.
2.
That
those patterns are accurately transferred to human skin consistently.
3.
That
defining characteristics of that pattern can be accurately analysed to exclude
or not exclude individuals as the source of a bitemark.
The report also finds that there is a
lack of empirical research on the accuracy and reliability of bitemark
analysis. This is due in part to the difficulty of conducting controlled
studies on bitemarks, as they are often found in the context of violent crimes.
The report makes several recommendations for improving the reliability and
validity of bitemark analysis, including:
a)
Conducting
more empirical research on the accuracy and reliability of bitemark analysis.
b)
Developing
standardized protocols for the collection, preservation, and analysis of
bitemarks.
c)
Increasing
the transparency of bitemark analysis procedures.
d)
Educating
law enforcement and the courts about the limitations of bitemark evidence.
The report concludes that bitemark
analysis is a promising forensic tool, but that more research is needed to
establish its scientific foundation and reliability.
THE
VALIDITY OF BITE MARKS:
The validity of bite marks in Indian
courts is a complex issue. There is no clear consensus on whether bite mark
evidence is reliable enough to be used as the sole basis for a conviction. On
the one hand, bite marks can provide valuable information about the identity of
the perpetrator. The shape and size of teeth, as well as the spacing between
them, are unique to everyone. This means that bite marks can be used to exclude
suspects from a crime scene, or to identify a suspect if there is a match. On
the other hand, there are several factors that can make bite mark evidence
unreliable. The condition of the bite mark can deteriorate over time, making it
difficult to match to a suspect’s teeth. The bite mark may also be contaminated
by other factors, such as dirt or food, which can make it difficult to identify
the perpetrator. In addition, there is a lack of scientific consensus on the
reliability of bite mark analysis. Some studies have shown that bite mark
analysis can be accurate, while others have shown that it is not reliable
enough to be used in court. As a result of these factors, the validity of bite
marks in Indian courts is still being debated. Some courts have admitted bite
mark evidence, while others have excluded it. Ultimately, the decision of
whether to admit bite mark evidence is up to the judge in each case.
Here are some additional points to
consider:
a)
Bite
mark evidence is often used to corroborate other evidence, such as eyewitness
testimony or DNA evidence.
b)
The
reliability of bite mark evidence can be improved by taking careful photographs
of the bite mark and by obtaining dental impressions from the suspect.
c)
Bite
mark analysis is a specialized field, and it is important to choose an experienced
expert who is familiar with the latest research.
DENTAL SCIENCE IN LEGAL CONTEXT:
Forensic odontology encompasses the
application of dental science to the legal field. There are four major areas of
interest that it may be broadly divided into:
Dental
identification of the Unknown Body:
This involves comparing dental records and X-rays with those of a deceased
individual (or remains that cannot be identified by other means) to establish
their identity.
v Trauma and
the Oral Tissues: This area focuses on interpreting
oral injuries and their relevance to legal matters.
v Dental
Malpractice and Negligence:
Here, the treatment provided by a dentist is analysed, and the findings are
presented in a court of law in cases involving allegations of malpractice or
negligence.
v Bite Mark
Comparison: This controversial aspect involves
comparing bite marks found on a victim with the dental impressions of potential
criminal suspects.
Among these areas, bite
mark comparison has been particularly contentious within the field of forensic
odontology.[24]
FACTORS
INFLUENCING THE EVIDENTIARY VALUE OF BITE MARKS IN FORENSIC ANALYSIS:
The evidentiary value of bite marks
in forensic analysis can be significantly influenced by several factors. These
factors include the distortion of the skin, degradation of DNA, time interval
between the bite and examination, movement, overlapping of bite marks, and
more. Human dentition consists of 32 teeth, each with five anatomical surfaces,
resulting in a total of 160 dental surfaces with individual characteristics.
The evidentiary value of bite mark evidence is influenced by the surface on
which the bite mark pattern is transferred. Bite marks are commonly found on
the skin of victims and occasionally on food items. However, skin is not an
ideal material for accurately capturing dental patterns. Compared to modern
dental materials, it provides a less clear medium for recording human
dentition. Skin is highly viscoelastic, which means that indentations created
by teeth during biting tend to rebound. This rebound effect hampers the skin’s
ability to accurately retain the three-dimensional structure of the biting
edges of teeth, resulting in a lack of comprehensive records.[25]
However, during bite mark analysis, only a limited number of teeth (typically
four to eight) are often present in the bite mark evidence. Moreover, only the
edges of the front teeth contact the skin, meaning that the information
recovered from bite marks is considerably less comprehensive compared to other
forensic identification techniques such as fingerprints or DNA. Additional
factors such as restorations, decay, malposition, and injuries contribute to
individuality but provide limited information during bite mark analysis.
Research studies have shown that even models of dentition from different
individuals may exhibit indistinguishable similarities when considering the
front six teeth. The substrate onto which bite marks patterns are transferred
also impacts the evidentiary value. Skin, the most common surface for bite
marks, is an inadequate medium for accurately recording dental patterns
compared to modern dental materials. Skin is highly viscoelastic, causing
indentations left by teeth during biting to rebound and distort, leaving no
potential record of the three-dimensional structure of the biting edges. This
distortion is attributed to the elastic fibres in the dermis, which deform
under pressure and subsequently recoil back to their original position. The
degree of distortion depends on factors such as age and anatomical location.
Additionally, bite marks are essentially bruises that consist of blood from
crushed capillaries, further affecting precise measurements during bite mark
comparison. The pliability, elasticity, and reactivity of skin pose significant
limitations to the validity of forensic odontology, as highlighted in the
National Academy of Sciences (NAS) report[26].
Bite mark distortion on the skin is
influenced by the position and movement of both the biter and the bitten person
during the injury. Violent crimes involving biting often occur during struggles
when the skin is stretched, resulting in the formation of bite marks. However,
when the skin returns to its normal shape, the transferred bite marks become
distorted to an unknown extent. Distortion can also occur during photography
and post-mortem procedures due to body movement and changes in position.
Research studies have discussed the impact of Langer’s lines (tension lines
indicating collagen Fiber orientation) on bite mark appearance, noting that
bites crossing these lines are more prone to distortion. The biting process and
the skin’s response to trauma can lead to further distortion due to edema and
subsequent resorption.
Bite mark evidence contains valuable
biological material, specifically DNA derived from leftover oral epithelial
cells. However, the presence of nucleic acid-degrading enzymes in saliva,
combined with the skin’s temperature, can accelerate the degradation of DNA in
living victims. Environmental factors also affect DNA integrity. Photographic
distortion is another concern in bite mark analysis, particularly when the bite
marks are not recorded with the American Board of Forensic Odontology (ABFO)
scale at a 90° angle. Inadequate documentation may lead to photographic distortion.
Some skin conditions, such as pityriasis rosea, can mimic bite marks, adding
complexity to the analysis. Distinguishing bite mark patterns from those caused
by animal or insect predation can also be challenging. Overlapping bite marks
present further difficulties during comparison, and factors like clothing, bite
force, and victim movement can affect the appearance of bite marks.
Bite marks undergo shape and clarity
changes within a relatively short period, both in living individuals and after
death. The time interval between the injury and examination can introduce
distortion due to contraction and healing artifacts, particularly in cases of
lacerations and abrasions. Such changes affect the dimensions and appearance of
bite marks. Studies conducted using pig skin and human dentition have
demonstrated that incorrect identifications increase significantly over time.
Additionally, the skin and flesh undergo changes after death due to
decomposition, animal predation, insect activity, and other environmental factors.
Considering the inevitability of distortions, the comparison of bite marks on
skin with dentition raises significant questions about its reliability in
forensic analysis.
Forensic odontology in India:
A branch of forensic science
identified as forensic odontology uses dental expertise to identify individuals
and conduct legal investigations. Forensic dentistry is a relatively new but
fast-growing specialty in India that has been extremely helpful in both
criminal and civil matters.
Although forensic odontology has a
long history in India, one of the oldest incidents of identification by teeth
was recorded in 1191. The artificial anterior teeth on M. Raja Jayachandra
Rathore of Canouj’s body made it easy to identify him after he passed away on the
battlefield. One of the first cases of dental identification in India is
thought to have occurred in this case.
The Nirbhaya case, also known as the
Delhi gang rape case, which took place in 2012, is a notable and well-known
case involving forensic odontology in India. On January 1, 2013, the Delhi
Police requested assistance from the forensic odontology division in Dharwad in
the “Nirbhaya” case, which occurred in New Delhi. The investigation of the bite
marks discovered on the victim required assistance. The next day, a
sub-inspector from the Vasant Vihar Police Station went to the SDM College of
Dental Sciences & Hospital in Dharwad personally and handed over photos of
the bite marks on the victim’s body as well as dental models of five adult male
suspects who were thought to be involved in the case. Bite marks are frequently
discovered in sexual assault-related crimes and, like fingerprints, they might
resemble the perpetrator’s teeth. Five to six bite marks were found on the
victim after inspection, which were meticulously verified and compared with the
dental records of the five suspects. During the investigation, a 2D digital
analysis on a computer was performed. A complete report that was
delivered to the police after five days of investigation found that two of the
suspects’ dentition matched some of the bite marks. The doctor was called as an
expert witness to the Saket Court in New Delhi on May 6, 2013, where the
defence attorneys cross-examined him. The honourable judge accepted the
submitted testimony and report was significant in leading to the conviction of
two of the defendants. Additionally, in its ruling on May 5, 2017, the Supreme
Court of India upheld the analysis and report. The significance of forensic
odontology in criminal investigations and legal proceedings is demonstrated in
this case.
The Paper Mill Colony Case (2012):
In 2012, a
startling incidence involving a horrifying crime against a woman took place in
India. Visible bite marks on the victim’s body were found, and these marks
served as critical evidence in the inquiry. Odontologists were among the
forensic specialists enlisted to examine the bite marks to compare them with
the dental records of prospective suspects. The professionals were able to
identify the distinctive features of the bite marks and associate them with a
specific person by using cutting-edge dental examination techniques. The
identification and conviction of the criminal guilty for the crime depended
heavily on the forensic evidence.
The Perumbavoor Case (2016):
The
brutality of the Perumbavoor Case in Kerala, India, in 2016 horrified the
entire country. The body of a young woman who had been raped and killed was
discovered, and bite marks on it served as vital evidence in the investigation.
To thoroughly investigate the bite marks and take teeth impressions of
prospective suspects, forensic odontologists were called in. The experts were
able to establish a direct connection between the bite marks discovered on the
victim and the dental features of the perpetrator through thorough study and
comparison. The authorities were able to identify and apprehend the criminal
with the use of this crucial evidence, ensuring that he was held accountable
for his acts in a court of law.
The Paper Mill Colony Case (2012): In
2012, a startling incidence involving a horrifying crime against a woman took
place in India. Visible bite marks on the victim’s body were found, and these
marks served as critical evidence in the inquiry. Odontologists were among the
forensic specialists enlisted to examine the bite marks to compare them with
the dental records of prospective suspects. The professionals were able to
identify the distinctive features of the bite marks and associate them with a
specific person by using cutting-edge dental examination techniques. The
identification and conviction of the criminal guilty for the crime depended
heavily on the forensic evidence.
Forensic Odontology International:
In numerous international cases,
forensic odontology has also been crucial in assisting with identification and
offering important evidence. One such instance involved identifying John Wilkes Booth, the man who killed Abraham Lincoln.
Following the killing, as Booth fled, there were claims that he managed to
avoid capture. Booth’s body was unearthed to confirm his death, and his family
dentist, Dr. William Merill, recognized him based on his unusual jaw and the
gold restorations he had only recently created for Booth. The identification of
President John F. Kennedy’s assassin Lee Harvey Oswald was another well-known
instance in which forensic odontology was used. Two days after the murder,
Oswald was found and later shot dead by Jack Ruby. When questions and rumours
regarding Oswald’s identity surfaced fourteen years later, his body was dug up
and examined in 1981. Antemortem dental records were used by forensic
odontologists to establish Oswald’s identification and put an end to the
rumours.
In cases of person identification in
mass casualties or incidents involving prominent personalities, forensic
odontology has also been applied. The identification of Saddam Hussein’s sons, Uday and Qusay Hussein,
who were murdered by the US forces in 2003, serves as an illustration of this.
Dental records were used to identify the bodies despite being severely charred,
demonstrating the significance of forensic odontology in such cases.
These instances highlight the
important contributions forensic odontology has made both nationally and
internationally, with a focus on its function in the administration of justice,
identification, and criminal investigation.
In the
case of Doyle v. State in Texas[30]
in 1954, In a US court, dental evidence was used in an unconventional manner.
The burglary suspect, Doyle, is suspected of leaving his teeth marks in a
cheese slice that was only partially consumed. The evidence was examined by
dentist Dr. William J. Kemp, a qualified dental expert for the State of Texas.
The suspect was requested to bite into a different piece of cheese so that the
bite marks could be compared. Dr. Kemp testified that Doyle was responsible for
the crime because the bite patterns on both pieces of cheese matched. Forensic
dentistry is a relatively new and developing subject in India. Despite having a
long history in forensic science, the country is still in the early phases of
applying scientific and technology approaches for crime detection and
investigation as well as for the administration of justice. However, forensic
odontology is proving to be extremely helpful in both criminal and civil cases,
providing exciting chances for the legal system to advance[31].
One notable case in Florida’s legal
history is the bite mark case involving Ted Bundy. This case played a
significant role in solving the murder of Lisa Levy and Martha Bowman. On
January 15, 1978, these two young girls were brutally killed using a wooden club.
A witness saw a man with his face covered fleeing from the scene. The
investigators were faced with a gruesome and merciless murder. Levy was
strangled, beaten, and raped, while Bowman was strangled and severely beaten.
Surprisingly, there were no signs of struggle, and the crime scene had been
wiped clean, with the murder weapon missing. The investigators suspected that
Ted Bundy, known for his accuracy, was responsible for these killings. However,
in a court of law, evidence is essential, and mere presumptions are not
sufficient. The investigators collected various pieces of evidence, including
blood, some smudged prints, and sperm samples, but these were inconclusive. It
was the recovery of a bite mark that became the centrepiece of evidence during the
trial. The bite mark found on Lisa Levy’s buttock and breast was carefully
documented and photographed with a yellow scale as a reference. Dental
impressions were taken from the suspects for comparison with the suspicious
bite mark, but Bundy refused to cooperate. A search warrant was obtained,
allowing investigators to obtain the impressions by any means necessary. Dr.
Souviron, an experienced dentist, took photographs of Bundy’s upper and lower
jaw, noting the distinct uneven pattern. These dental photographs were then
compared to the photographs of the impression on Lisa Levy’s buttock, as it was
more prominent than the one on her breast. The analysis focused on the shape of
the teeth, their sharpness, the applied pressure, and the arrangement of the teeth,
considering that the tissues near the impression had deteriorated over time.
Peculiar features were identified, which contributed to Bundy being found
guilty. The expert witness explained that the attacker had bitten twice,
keeping the upper jaw in the same position while moving the lower jaw sideways.
Bundy was ultimately sentenced to death by electric chair for his crimes. This
case serves as an example of how bite mark evidence and expert testimony played
a crucial role in securing a conviction[33].
In 1692, during the Salem Witch Trials, Rev. George
Burroughs was accused of witchcraft and
conspiring with the Devil, with biting his victims supposedly being evidence of his
crimes. His bite marks and the bite marks of other people were compared to the
victim’s marks. The judges readily accepted the bite marks as evidence and this
was the first time in what would become the United States that bite marks were
used as evidence to solve a crime. He was later convicted and hanged. About two
decades later, he was exonerated by the State, and his children were
compensated for the wrongful execution.
One of the first published accounts
involving a conviction based on bite marks as evidence was the “Gorringe case”,
in 1948, in which pathologist Keith Simpson used bite marks on
the breast of the victim to seal a murder conviction against Robert Gorringe
for the murder of his wife Phyllis. Another early case was Doyle’s
case 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 burglary. The defendant was later
asked to bite another piece of cheese for comparison. A firearms examiner and a
dentist evaluated the bite marks independently and both concluded that the
marks were made by the same set of teeth. The conviction, in this case, set the
stage for bite marks found on objects and skin to be used as evidence in future
cases.
Another landmark case was People v. Marx[36],
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. These samples along with other models 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.
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Article Information
RELIABILITY AND VALIDITY OF BITE MARK ANALYSIS: CRITICAL EXAMINATION AND IMPROVEMENT OF CURRENT PRACTICES
Authors: SAHANA ASHOKUMAR
- Journal IJLRA
- ISSN 2582-6433
- Published 2024/03/02
- Issue 7
About Journal
International Journal for Legal Research and Analysis
- Abbreviation IJLRA
- ISSN 2582-6433
- Access Open Access
- License CC 4.0
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