DEPARTMENT OF ORAL & MAXILLOFACIAL PATHOLOGY

DR. ABHAY KUMAR FORENSIC ODONTOLOGYBITE MARKS

FORENSIC ODONTOLOGY IN CRIME INVESTIGATIONS :•BITE MARKS•LIP PRINTS

IMPORTANCE OF BITE MARK IN CRIME INVESTIGATIONS : - Bite mark can accurately depict the unique pattern of Biter’s teeth - Helps to identify the culprit or exclude an innocent person

Picture of Abdomen Bite

DIFFERENCE BETWEEN A HUMAN OR AN ANIMAL BITE human animal

Arch size and shape broad, U- shaped, circular or oval Narrow , anterior aspect , V shaped & elongated

Teeth Broad central and narrow lateral incisors; more blunt

Broad laterals, narrow centrals, sharper, longer canines

Injury pattern Commonly bruishing ; laceration and avulsion less common

Severe laceration and avulsion , greater skin damage

sites In females usually on breast, abdomen, nipple, thigh, back & shoulder in case of sexual assault in fight & violence

Extremities such as feet , legs , hands, arms ,exposed skin

Cat BiteDog Bite

Monkey Bite

Human Bite

• BITE MARK defined as: “The mark made by human or animal teeth in the

skin of alive people, cadavers or unanimated objects with relatively softened consistence”

• A mark caused by the teeth either alone or in combination with other mouth parts

WHAT IS A BITEMARK?• Bitemark considered as :

– A physical alteration in a medium caused by the contact of teeth

– A representative pattern left in an object or tissue by the dental structures of an animal or human

• Cutaneous Human Bitemark:– An injury in skin caused by contacting

teeth (with or without the lips or tongue) which shows the representational pattern of the oral structures

• Bite mark analysis, in a forensic investigation, can elucidate the kind of violence and the elapsed time between its production and the examination

• Indicates , if the bite was produced intra-vitam or post-mortem

• In case of several bite marks, helps in identification of the sequence

• By observing, analyzing and interpreting, the bite marks constitute a important medical-judiciary proof in some cases of offense and help in suspects exclusion or point out the culpability elements

• Size , shape and pattern of the incisal or biting edges of upper and lower anterior teeth to be specific to an individual

IS BITEMARKS USEFUL?

• Bitemarks used to carry out bitemark analysis i.e. a comparison of a known person’s dentition to a patterned injury which appears consistent with a bitemark

• This type of comparison is used to confirm or eliminate the identity of a suspect in relation to the bitemark

1) 3rd Molar (wisdom tooth)

2)2nd Molar (12-yr molar) 3)1st Molar (6-yr molar) 4)2nd Bicuspid (2ndpremolar) 5)1st Bicuspid (1st premolar) 6)Cuspid (canine tooth) 7)Lateral incisor 8)Central incisor

.

17) 3rd Molar (wisdom tooth) 18) 2nd Molar (12-yr molar) 19) 1st Molar (6-yr molar) 20) 2nd Bicuspid (2nd premolar) 21) 1st Bicuspid (1st premolar) 22) Cuspid (canine/eye tooth) 23) Lateral incisor 24) Central incisor 25) Central incisor 26) Lateral incisor 27) Cuspid (canine/eye tooth) 28) 1st Bicuspid (1st premolar) 29) 2nd Bicuspid (2nd premolar) 30) 1st Molar (6-yr molar) 31) 2nd Molar (12-yr molar) 32) 3rd Molar (wisdom tooth)

9)Central incisor 10)Lateral incisor 11)Cuspid (canine tooth) 12)1st Bicuspid (1st premolar) 13)2nd Bicuspid (2nd premolar) 14)1st Molar (6-yr molar) 15)2nd Molar (12-yr molar) 16)3rd Molar (wisdom tooth)

- Tooth arrangement is different in everyone- Teeth can be arranged in 1.36 x 1026 combinations (12 anterior teeth combination)

- The Uniqueness is reproduced in the bite marks

Evidential Value of Bitemarks

• By establishing the uniqueness of the biter's teeth and then applying those unique properties to the bite pattern, a degree of confidence relating the biter's teeth to the injury pattern is obtained

• This opinion can range for excluded (the suspect did not do the

biting) to likely and without a doubt (the bite was witnessed and there is not question the suspected biter inflicted the bite)

• Despite the unique nature of the position and arrangement of the

human teeth, it is usually easier to rule out a suspect as a potential biter than it is to include a suspect as a potential biter

Various Bite Marks

CLASSIFICATION OF BITE MARKS

1) Cameron and Sims’ classification:- Based on the type of agent producing the bite

mark and the material exhibiting it- Agents: Human Animal- Material: Skin , Body tissue Foodstuff Other Materials

• MacDonald’s classification:- Suggested an etiologic classificaation- Pertinent for human bite marks1) Tooth pressure Marks- - direct application of pressure by teeth causes marks on

tissue - by incisal or occlusal surfaces of teeth2) Tongue Pressure Marks- - tongue presses tissue against rigid areas (lingual surface of

teeth) - combination of sucking and tongue thrusting involved - known as suckling marks

3) Tooth Scrape Marks- - Scraping of teeth across the bitten material - Caused by anterior teeth - Scratches or superficial abrasions

• Webster’s classification: - bite marks on foodstuff1) Type I - food item fractures readily with limited depth of tooth

peneteration, e.g. hard chocolate2) Type II - fracture of food fragment with considerable penetration of

teeth e.g. bite mark in apple and other firm fruits3) Type III - complete or almost penetration of the food item with slide

marks , e.g. cheese

BITE MARK APPEARANCE

CONTUSION (bruises) :-Edema subsides and subcutaneous bleeding apparent-Most common presentation of bite marks-Appears reddish or purplish discoloration of skin surface

LACERATION:- Breakage in the integrity of skin surface , due to great intensity of bite

ABRASIONS

AVULSION:- Extreme form of bite mark injury - part of the tissue is bitten off

TYPES OF INJURYINDENTATIONS :-Ideal for bite mark analysis-Seldom persist for more than a few minutes unless the victim is dead

IDENTIFYING THE INJURY AS A BITE MARK

• Characteristics for human bite marksGross features:- Circular or elliptical mark , on skin with a central area of

ecchymosis- Caused by upper and lower arches and ecchymosis due to

sucking action- Injury from other things differ from typical bite mark

Class features:- Made by different classes of teeth are distinct- Allows to differentiate tooth type within a bite mark- Incisors – Rectangular Canines – Triangular or Rectangular(depending upon amount of attrition)

Premolars & Molars – Spherical or Point - shaped

Bite mark appearance varies

Individual features:- Class features having fractures , rotations , spacing etc- Bite marks are distinct

The typical bitemark

Normal Adult Human Teeth

PHYSICAL CHARACTERISTICS :

•distance from cuspid to cuspid

• tooth alignment

• teeth width, thickness, spacing

• missing teeth

• wear patterns including chips and grinding

• dental history including fillings, crowns, etc.

Site of bite marks

• Breast - 40%• Arms & Legs – 27%• Head & Neck – 13%• Genitals – 6%• Abdomen – 2%

BITE MARKS OCCURS

SEX CRIMES FIGHT AND ABUSE

MECHANISM OF BITE MARKS

• Result of teeth pressure on skin (combination of force )

• Starts with mandibular closure, followed by suction of skin (as a negative pressure) and action, in the opposite direction, thrusted by the tongue; hence, have projection on teeth incisor and lingual surfaces

• In general, a person bites an object, the superior teeth hold the object while the inferior ones cut it

• The mark left by the superior teeth, is extremely relevant in order to provide information such as:

Dental alignment, Size and Shape of dental archs

• Bite mark generally - circular or ovoid, and can have an appearance similar to sweet dough, like a doughnut or the dental arch may be registered as horseshoe shape patches

• Human adult dentition consists of 32 teeth and each one of them has its own size, shape and features

• Unique in every individual due to extractions, bad alignment, bad positioning, bad development, spaces, dental fractures, restorations and other numerous factors

• Therefore, action of the dental arch on the skin may produce many kinds of lesions, as the dental elements act as incisive instruments or even incisive-cut

• Evidence of a bite mark is usually crucial to establish that two subjects have been involved in a violent contact in a crime scene

• Greatest challenge in Forensic Dentistry are bite marks found in human skin, because of the distortion presented and the time elapsed between the production and the analysis

• Factors that can affect the structure of the lesions produced by bite marks, include:

Applied force, Bite duration and Movement between tissues and teeth

BITE MARK INVESTIGATION

Preliminary questions

• Is the injury a bite mark?• Was it caused by human teeth?• How is the BM clarity?• Caused by adult or child?• Does it correspond to the crime?• Are there individual characteristics?

Collecting evidence from victim

• History & Physical examination• Case Demographics (Case no., name of victim , age , sex , date ,

examiner’s name)

Visual examination :- Visual examination and documentation orientation and location of the mark type of injury colour , size and shape contour, texture ,and elasticity of the bite site difference between upper and lower arches and

between individual teeth

PHOTOGRAPHY

•Provides a permanent record of bite marks

•Orientation photography – location of bite mark in body

•Close up photograph ABFO No. 2 scale

•Another closeup photograph without scale

•Should be taken perpendicularly to injured area

•In case of alive victim, photographs can be repeated every 24 hours for 3-4 days to record progressive changes in appearance of bite marks

Photography

SALIVA SWABS :

• Taken from bite mark or if bitten from clothes then collect it from clothes

• Saliva have WBC’s & sloughed epitheloid cells which are potential source of DNA

• Cotton swab moist with distill water used for swabbing

• Swab is air dried at room temperature (30mins), placed in labeled envelopes and refrigerated to prevent DNA degradationand bacterial growth

• Use of high intensity alternative light source(Uv light) used to locate stains from body fluids enable saliva traces to recver , in absence of visible bite marks

IMPRESSIONS– For tooth indentations

Material of choice – Vinyl Polysiloxane

-Imperession material reinforced with dental stone, auto polymerizing acrylic or impression compound to prevent dimensional change

PRECAUTION – Owing to the elastic nature of skin, indentation soon disappear as skin regains its original contour

Evidence collection from victim• Visual examination & documentation ( BM location , size , shape , colour , injury type)- Take Pix , Saliva , Swab , make Impression

Wrong Photograph

Collecting evidence from a suspect

• Obtain Consent

• Clinical Examination

• Photographs

• Casts/Bite Sample

• Saliva Swab

BITE MARK ANALYSIS AND COMPARISON

• ONE OF A SPECIFIC ELEMENT OF FORENSIC DENTISTRY –

BITEMARK ANALYSIS

A dentist is required to compare the impressions and bruises left in the skin by one person biting another to a suspect’s teeth

Bitemark Analysis

• In a bitemark comparison, you are looking for and matching unique features between the bitemark and exemplar castings. These features may include:– Gaps– Rotation (angle)– Size of teeth (e.g. width at tip)– Width from tooth to tooth (e.g. cuspid to cuspid)

How are bite marks analyzed?Over 20 different methods of bitemark analysis are thereThe most common used are:1.Comparing an acetate overlay manually fabricated from study

models to a life size photograph of the wound2.Comparing study models to a life size photograph of the wound3.Comparing an acetate overlay manually fabricated from bites in

wax to a photograph of the wound 4.Comparing an acetate overlay manually fabricated from x-rays of

radiopaque material placed in a wax bite to a life size photograph of the wound

5. Comparing an acetate overlay manually fabricated from a photocopy of study models to a life size photograph of the wound

Sample Analysis

Sample AnalysisBitemark : Upper Jaw Distance Suspect; Upper Jaw Distance

Cuspid to cuspid Cuspid to cuspid

38mm 42mm

 

Bitemark: Distance Suspect: : Distance

Tooth 6 to Tooth 10 Tooth 6 to Tooth 10

 44.25mm 39.65mm

Angle: + 14.5 Degrees Angle: + 12.52 Degrees

ACETATE OVERLAYS• Most of these techniques involve the fabrication of an

acetate overlay• An acetate overlay is an outline of the biting edge of

someone’s teeth as traced onto and seen on a clear transparency

• Fabricated in a number of ways• A review of the literature has found over 15 methods• Include tracing from dental models, photographs, wax

bites, photocopies

COMPUTER PROGRAMS

• Have been developed to overcome some of these problems• Theoretically they can;

– Correct for distortion– Generate the overlay objectively– Carry out the comparison objectively– Reproduce the overlay

Computerized re-construction of bite mark

BITE MARK ANALYSIS & COMPARISON

INDIRECTLY –

- By comparing the bite mark separately with the cast of the suspect

DIRECTLY –

- By computer software 3-D/CAD

Bite marks are photographed with a scale- Bite marks on skin are taken over repeated intervals

Casts of impression are takenImpression traced onto transparenciesCasts of suspects teeth are takenComparison between suspect cast and bite mark

Computer Odontology Automatic dental code matching

- Bites are run through the computer to find a match

OdontoSearch- Compare a data base of missing peoples, felons, government workers

Automatic dental identification system- A few minutes will produce a list of people who have the same dental code number

3D Bite mark analysis- 3D scans of dental casts are used to generate overlays using various pressure and deviation- The overlays are compared with the photograph of the bite marks

SUMMARY:

• Identification of bite marks on victims

• Comparison of bite marks with teeth of a suspect

• Identification of unknown bodies through dental records

• Age estimations of skeletal remains

• Victim identification through DNA analysis

Analyse the bite mark

Analyse suspect’s casts & delineate bite edges

Bite edges superimposed on BM

CHALLENGES IN BITE MARKS INVESTIGATION• Two bite marks , same bitter!

1

2

Considerations &

Limitations

CRITISISMS OF BITEMARK ANALYSISIn recent years, Bite Marks questioned as a reliable scientific

tool ??????????Based on:1. Numerous methods of fabrication2. Relies on manual fabrication3. Subjective element in fabrication4. Subjective element in comparison5. Distortion which occurs

- As a result, suggested that bitemark analysis using acetate overlays are inaccurate, subjective and non-reproducible

Accuracy of Skin as a Substrate for a Bitemark• Threshold variable in bitemark analysis is the fact -In cases of physical assault having skin injuries, anatomy and

physiology of the skin, and the position the victim affects detail and shape of the bitemark

• No significant way to experimentally control or establish the amount of positional variation in an actual bitemark case

• Reality - skin is usually a poor impression material No significant tests have been published on this subject since

1971 in the odontology literature

Consider the Following

- Outlines of the same set of teeth-Different perimeter shapes depend on how far the teeth are pressed into the test substrate

Report & Conclusion• Description of evidence , comparison and degree of

certainty of link between BM & suspect’s teeth• Grades of conclusion:- Reasonable medical certainty that it is the biter (Definite Biter)- Probably the biter- Possibly the biter- Excludes the suspect- Insufficient evidence

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