Issues in Human and Animal Bite mark (Bitemark) Analysis
Please check the latest forensic science book by Dr. Mike Bowers.
Forensic Dentistry: A Field Investigator's Handbook. 2004. The Publisher is Academic Press (Elsevier Publishing). It is available at Amazon.com
Write us for information on our 2nd Edition of Digital Analysis of Bite Mark Evidence published in September 2003. Available entirely in CD format.
April 20, 2004
Greetings,
I know a majority of you have never seen a human bitemark ( aka bite mark), but I hope the material I present will provide some light on the subject. The pictures on this website are unfortunately not at high resolution due to the file size limitations and downloading time required for high-resolution files. A excellent legal review on digital imaging and forensic evidence is available from the FBI Forensic Science Communication Newsletter. In addition, scroll down past the hyperlinks for the Table of Contents for a large section on bitemark analysis for Forensic Investigators.
Articles written by Dr. Johansen and myself have published in the April 2001 Forensic Dentistry issue of Dental Clinics of North America, the FBI newsletter Forensic Science Communication, the next edition 2004) of Medical Legal Investigation of Death by Spitz and Fisher, and the 2002 Edition of Modern Scientific Evidence (West Publishing) by Faigman, Kaye, Saks, and Sanders.
Digital Correction of Bite Mark Photographic Evidence |
Dr. Bowers 2004 Book on Forensic Odontology to be published by Academic Press |
Curriculum Vitae and Articles |
Creating Computer Generated Exemplars of Suspect Dentition
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Ted Bundy Bite Mark Case |
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December 2000 Bite Mark Article: Arguments on the Individuality of Teeth
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The Torgerson Case The Detection and Analysis of Photographic and Anatomical Distortion
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http://forensicdentistryonline.com/
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Bite Mark Literature 1960 to 1998
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Table of Contents: Bite Mark Analysis for Forensic Investigators
The Accuracy of Skin as a Substrate for a Bite Mark
Bruising as a Means of Aging Bite Marks
Bruising and Other Considerations
Arguments for the Individuality of Human Teeth
How Attorneys Regard Expert Witnesses
Proposed Limitations on Bite Mark Opinions
Methods of Comparison in Bite Mark Identification
The Use of Digital Analysis in Bite Marks
The Interplay of DNA Analysis and Bite Mark Evidence
Bite Marks: Measurement of Physical Characteristics of Two and Three Dimensional Evidence
Digital Control of Photographic Distortion
Evaluation of Photographic Distortion
Creating Computer Generated Exemplars of Suspect Dentition
Metric Analysis of Bite Mark Injuries
Bite Mark Literature Citations 1960-1998
In order for a physical comparison to be successful, this is in odontology as well as other forensic disciplines, the Questioned (Q) evidence photograph ( the bitemark) has to be accurately reproduced. The photograph must be created in a life-size dimension. Once this is done the Known (K) evidence (in this case, the plaster casts of the defendant's teeth) are used to analyze similarities and dissimilarities in shape, size, positioning, etc, seen in the bitemark. The first rationale you must realize is this next section.
The Accuracy of Skin as a Substrate for a Bitemark
The threshold variable in bitemark analysis is the fact that, in cases of physical assault having skin injuries, the anatomy and physiology of the skin, and the position the victim was in affects the detail and shape of the bitemark. There is one article from the early 1970's from England by Devore that showed how the positioning of the test bite (actually it was an inked circle) on a bicep varied whether the arm was flexed or pronated. In my recent case, the buttock is considered an area that does not show much variation in shape, so this was not an issue. What is significant is that there is no way to experimentally control or establish the amount of positional variation in an actual bitemark case. You can't use the actual victim (usually) and a deceased individual will also not be available. The bottom line is that skin is usually a poor impression material. No significant tests have been published on this subject since 1971 in the odont literature.
What also is a. major issue in bite mark cases is the amount of detail present in the bitemark. The injury may only be a series of reddened bruises at the time of the original photograph. If there were no three dimensional (i.e., tooth indentations) that could be used for increased detail the vagaries of inflammation and tissue response to trauma. The seminal California case for bitemarks was in 1975 (People v Marx). This case involved a deep bite made on a nose that had distinctive three dimensional features.
Bruising and Other Considerations
Recognition of the fact that bruising is actually subcutaneous bleeding demands that the investigator not assume that the reddened areas that appear to be teeth are an accurate representation of individual teeth. This is where the association of all the marks with each other is extremely important. I recommend that the bitemark be thoroughly analyzed FIRST. That means measurements, angles, and other features should be convincingly studied before any suspect(s) teeth be viewed. This provides a modicum of control where the determinations of the forensic value of the bitemark are establish prior to the dentist comparing the Known evidence. The reality of two dimensional (i.e., bruises) bitemarks is that individual (i.e., unique) features are extremely rare. The details of intertooth spaces, rotations, and blank spaces between teeth are the principal features of this type of injury.
Arguments for the Individuality of Human Teeth
The second foundation of bitemark analysis is that the total arrangement of a person's dentition creates a dental "profile" of sorts. An attempt to prove this was in 1982 when a small study of five identical twins was done at UCLA. This has nothing to do with dental restoration shape and position which are used in identification of missing and unknown individuals. There are experimental problems in this study involving the degree of depth necessary in a bitemark (the test used wax as an initial substrate) to differentiate one twin from another. In bitemark cases having only two dimensional markings, the conclusion of this 1982 study is irrelevant.
You probably can tell that I am not convinced that all bitemarks are of the level of forensic value necessary to identify just one individual. This is borne out by the fact that most dentist's opinions on a bitemark identification is of the "rule in" or "rule out" variety. This means the defendant(s) has some similarity to general features seen in the injury pattern. This is the weakest linkage possible and is not proof that the defendant made the bitemark, but "keeps the process" going. I will include the ABFO Bitemark Standards and Guidelines at the end of this section for your review on this subject.
What is typically argued at this stage is the forensic weight (value) that these characteristics possess. There is available orthodontic data on general dental characteristics such as racial variations in skeletal anatomy, jaw width, front tooth position, twisting of teeth (rotation), etc. They are seldom used in forensic cases and there are no specific studies from the forensic point of view on this topic. The dentist's opinion is based on "experience" and generally the jury believes or disbelieves this opinion based on other factors present in the dentist's testimony. These factors include years of experience, convincing court presentation, proper use of terminology, meticulous adherence to rules of evidence (i.e., not forgetting to bring his/her notes) and the like. This has been acceptable in court throughout the United States since 1954 (Doyle v. Texas). The advent of DNA profiling in criminal identification and certain US Supreme Court cases (Daubert, 1993; Kumho 1997) has awakened the courts to the nature of scientific proof versus personal opinion. This has developed generous conversation among the forensic identification disciplines (ballistics, toolmark analysis, odontology, fingerprints, anthropology) as to the real basis of testimonial expert opinion. This hasn't generated enough pressure to rule any of these opinions invalid in court at this date. What is significant, though, is the one area of identification called Questioned Document Examination that has been severely limited in its previous broad participation in court on the issue of handwriting analysis. This discussion is simply a trend that is slowly developing. Much more is to come, I believe.
Methods of Comparison in Bitemark Identification
The process of comparing the Questioned (Q) evidence to the Known (K) evidence is not succinctly controlled by the ABFO Standards and Guidelines. What is evident in the literature and in court is that dentists tend to adopt a method that other colleagues use. The testability of the accuracy of five common methods was started by Dr. David Sweet and myself in 1997 when we published an article in the Journal of the American Academy of Forensic Sciences. We found that there were differences in the outcome of these popular methods. These methods involve the duplication of the (K) evidence (teeth) in a manner which allows the outlines of the teeth to the placed OVER the photograph of the bitemark injury.
Previous articles had talked about the use of digital methods. (Sognnaes, and Naru). We used a desktop computer and an imaging program called Adobe Photoshop to create a transparent OVERLAY of the biting perimeters of the teeth (taken from scanning the dental casts). The older methods included hand tracing the tooth perimeters on clear acetate, Xeroxing the dental casts and then tracing the perimeters onto acetate, pushing the dental cast teeth into wax, and the use of xray film to capture the teeth impression which were filled with metallic powder. The motivation of this effort was to create data that could differentiate the variables in these methods and create an awareness that the use of the most accurate methods is mandatory in bitemark analysis. The results emphasize the accuracy of the computer method and the suggestion was advanced that hand tracing be abandoned. This has not been adopted by the ABFO.
The continuation of this effort by myself and Dr. Raymond Johansen recently produced a one day program in Santa Barbara on August 12, 2000 and a small (118 pages) manual on the subject of "Digital Analysis of Bite Mark Evidence." The manual is available from Amazon.com © at the link above.
The following material is an abstract of an upcoming textbook on Forensic Science. I will include a dog bite and the end. (dogs have eight front teeth in each jaw and VERY long canines). The entire ABFO Bitemark Standards and Guideline will complete this section.
I promise to give you more images of bitemarks and digital analysis as time and file size allows.
Figure eight: A very mean dog made this bite, Thanks to Dr. Gary L. Bell for this picture.
Bite mark Standards and Guidelines
©American Board of Forensic Odontology
ABFO BitemarkTerminology Guidelines
Collection of Bitemark Evidence from Suspect
Collection of Evidence from Victim
Certainty of Bitemark Diagnosis
Evaluation of Bitemark Evidence
Methods to Preserve Bitemark Evidence
Standards for Analytical Methods
Report Writing of Bitemark Evidence
Bitemark Analysis Guidelines History These guidelines are the result of a collective effort of the participants of the bitemark workshop of the American Board of Forensic Odontology assembled in Anaheim, California, February 18th through 20th, 1984. These guidelines are considered dynamic, not static, and will be modified as significant developments evolve. Careful use of these guidelines in any bitemark analysis will enhance the quality of the investigation and conclusion. Both in the case of a living victim or deceased individual, the odontologist should determine and record certain vital information.
Collection of Evidence From Victim It is assumed that evidence gathering from bitemark victims will be done with authorization from the appropriate authorities. It should first be determined whether the bitemark has been affected by washing, contamination, lividity, embalming, decomposition, change of position, etc.
back to ABFO Bite Mark Guidelines Collection of Evidence from Suspect Before collecting evidence from the suspect, the odontologist should ascertain that the necessary search warrant, court order or legal consent has been obtained, and should make a copy of this document part of his records. The court document or consent should be adequate to permit collection of the evidence listed below:
back to ABFO Bite Mark Guidelines Many methods have been used to study bitemark information and it is not the intent of these guidelines to mandate specific methods of analysis. As part of the analysis, it is suggested that the findings be evaluated in accordance with the following system. IMPORTANT NOTE: PLEASE READ BEFORE UTILIZING THE FOLLOWING "SCORING GUIDE": The January, 1988, Journal of Forensic Sciences published the following letter authored by Gerald L. Vale, DDS, DABFO, JD; Raymond D. Rawson, DDS, MA, DABFO; Norman D. Sperber, DDS, DABFO; Edward E. Herschaft, DDS, DABFO: Dear Sir: In the Oct. 1986 issue of the Journal, we published an article entitled "Reliability of the Scoring System of the American Board of Forensic Odontology for Human Bitemarks." It was felt that this article would generate discussion and feedback relative to the Board's scoring guide. Subsequent discussion and review have led the authors to the conclusion that much more work and consideration will be needed before a stable and accurate index is developed that can be widely applied. The presence of voluminous "statistics" in the article may have led eager readers to form conclusions that are unwarranted by the data at this time. We therefore urge all the professionals involved in forensic odontology to regard the summary and descriptive statistics in the referenced article as preliminary results only. While the Board's published guidelines suggest use of the scoring system, the authors' present recommendation is that all odontologists await the results of further research before relying on precise point counts in evidentiary proceedings. This does not mean that the investigator should not use the scoring system or other method of analysis that he or she may find helpful. It does mean that the authors believe that further research is needed regarding the quantification of bitemark evidence before precise point counts can be relied upon in court proceedings. Scoring Guide for Bitemark
Analysis General Instructions:
Gross If all teeth that can be individually identified in the bitemark are also present in the suspect’s mouth, award one point. This merely establishes that the mark could have been made by the suspect because he has the requisite teeth. If the number and assortment of teeth present is distinctive, award three points. Example: Suspect has teeth #'s 6, 7, 10, 11 and is missing #'s 8 and 9. This clearly reflected in mark. Award three points. If mark shows teeth that were not present in suspect’s mouth when bite was made, suspect is eliminated. If the size of the mark is approximately the same as the arch, award one point. If the size of the dental arch is unusual and the bitemark matches, award three points — in exceptional cases only. If the shape of the arch and bitemark are consistent, award one point. If the shape of the dental arch is distinctive and the bitemark matches, award three points. Example: Suspect has narrow, V-shaped arch and this is reflected in bitemark. Award three points. Tooth Position If the tooth and the corresponding tooth mark are in the same labiolingual position relative to the rest of the arch, award one point. If the tooth position is distinctive, award three points. Example: Six anterior teeth are visualized in the bitemark. All are well aligned except #7 which is 2mm to the labial. If this matches suspect’s teeth, award one point for each of the five well-aligned teeth and three points for tooth #7. Total score: 8. If the tooth and the mark show the same rotational position, award one point per tooth. If the rotation is distinctive, award three points. If mark is too diffuse to demonstrate rotations, do not score. If a tooth has a distinctive vertical position above or below the occlusal that is reflected in the bitemark, award one point. Example: Tooth #10 is diminutive (a "peg lateral"). All other anteriors are normal and touch the incisal plane. All anteriors are visualized in bitemark, but #10 barely marks. Award one point. If there is an identifiable spacing between the marking edges of adjacent teeth in the bitemark, award one point per space. Award three points if distinctive. Intradental Features NOTE: INTRADENTAL FEATURES CAN BE SCORED ONLY IN BITEMARKS REFLECTING DETAILED DENTAL ANATOMY. In the rare case in which the mesiodistal width of an individual tooth appears to be accurately registered in the bitemark, award one point per matching tooth. If the incisal edge of one or more anterior teeth has a distinctive curvature that is also evident in the bitemark, award a maximum of three points per matching tooth. Example: Incisal edge is extremely curved, or is absolutely straight and is similarly seen in bitemark. Award three points. If the labiolingual width of the tooth matches the mark, or if the worn incisal edge matches, award three points per tooth - only in a well-demarcated case permitting accurate comparison. Example: The mark clearly shows the cusp tip of a maxillary first bicuspid and one abraded (i.e. worn) lower incisor, which match suspect’s teeth. Award three points per tooth, totalling six points. If there are other distinctive features of individual teeth that cross-match, award three points per tooth. Example: Teeth #8 and #9 have fractured incisal edges that cause jagged marks in the skin. Award |
Award three points per tooth. Note that this feature might also have been awarded three points per tooth under mesiodistal width. ABFO Scoring Sheet for Bite Mark
Analysis Case Name: Features Analyzed Nbr. of Points Max. Mand. Discrepancy (if any) Gross All teeth in mark present in suspect’s mouth *One per arch Size of arches consistent (i.e. mark not larger than dental arch) *One per arch Shape of arches consistent *One per arch Tooth Position Tooth and tooth mark in same labiolingual position *One per tooth Tooth and mark in same rotational position (whether rotated or normal) *One per tooth Vertical position of tooth reocclusal plane matches depth *One per of mark (use only in unusual case) matching tooth Spacing between adjacent marking edges *One per space Intradental Features Mesiodistal width of tooth matches mark (use only if individual tooth is clearly marked) *One per tooth Labiolingual width of tooth matches mark OR attrition of edge matches mark **Three per tooth Distinctive curvature of tooth incisal edge matches mark (use only in unusual case) **Three per tooth Other distinctive features (fractured teeth, unusual anatomy) Three per tooth Miscellaneous Suspect has one edentulous arch and this is reflected in bite mark Three Total, each arch: Grand Total: *Three points if feature is significantly distinctive. **Only in case permitting accurate measurement. Signature Date 2/20/84 Committee on Bite Mark Guidelines ABFO Bitemark Terminology Guidelines back to ABFO Bite Mark Guidelines History In 1993, the ABFO Bitemark Workshop #2 Committee distributed a questionnaire on Bitemark terminology. About half of our members responded and provided the basis of the Bitemark Terminology survey reviewed at the three day Bitemark Workshop in San Antonio on February 12-14, 1994. Suggestions for modifications were made at that time and these were incorporated into the finished work-product which was accepted by the Diplomates of the ABFO on February 13, 1995, in Seattle, Washington. Rationale Please read Bitemark Terminology with the following perspective:
Terms Used to Describe and Interpret Bitemarks Bite mark vs. Bitemark The noun bite mark (two words) is used more frequently in the literature than bitemark (one word) and was preferred 3:1 in the ABFO survey. Dr. S. Miles Standish presented a cogent rationale for the single term, bitemark, as the preferred grammatical form. A professor of English at the University of Louisville concluded that, because language is a living thing, either term is acceptable. Bitemark implies a type of mark whereas bitemark connotes an entity unto itself and recognizable as such. Bitemark would be considered the more progressive term, signifying that odontologists have a sufficient body of work and evolved in similar fashion. Dr. Standish also adds that, when used as a compound adjective, bite mark is hyphenated as in Bitemark analysis. After evaluating all these opinions, it is the feeling of the ABFO that the meaning of the word in any of its forms is clear and there is no need for the ABFO to endorse a particular form. Component Injuries Seen in Bitemarks Abrasions (scrapes), contusions (bruises), lacerations (tears), ecchymosis, petechiae, avulsion, indentations (depressions), erythema (redness) and punctures might be seen in bitemarks. Their meaning and strict definitions are found in medical dictionaries and forensic medical texts and should not be altered. An incision is a cut made by a sharp instrument and, although mentioned in the Bitemark literature, it is not an appropriate term to describe the lacerations made by incisors. The term latent injury or wound was preferred over occult or trace wound when referring to an injury which is not visible but can be brought out by special techniques. A Characteristic (as it pertains to bitemarks) A characteristic, as applied to a bitemark, is a distinguishing feature, trait or pattern within the mark. Characteristics are two types, class characteristics and individual characteristics. Class characteristic: a feature, trait or pattern preferentially seen in, or reflective of, a given group. For example, the finding of linear or rectangular contusions at the midline of a Bitemark arch is a class characteristic of human incisor teeth. "Incisors" represent the class in this case. The value of identifying class characteristics is that, when seen, they enable us to identify the group from which they originate. For instance, the class characteristics of incisors (rectangles) differentiates them from canines (circles or triangles). If we define the class characteristics of human bites, we can differentiate them from animal bites. Via class characteristics, we differentiate the adult from the child bite or mandibular from maxillary arch. The original term "class characteristic" was applied to toolmarks and its definition has been modified to make it more applicable to bitemarks. Individual characteristic: a feature, trait or pattern that represents an individual variation rather than an expected finding within a defined group. An example of this is a rotated tooth. The value of individual characteristics is that they differentiate between individuals and help identify the perpetrator. The number, specificity and accurate reproduction of these individual characteristics determine the confidence level that a particular suspect made the bitemark. Bitemark Definitions Bitemark:
Cutaneous Human Bitemark:
COMMENT: These represent succinct, workable definitions. They lack 100% precision because they exclude the rare cases of denture markings and tooth contact marks without biting action. However, a definition that encompasses all possible tooth/mouth-to-medium contacts would be too cumbersome for practical application. back to ABFO Bite Mark Guidelines Description of the Prototypical Human Bitemark A circular or oval (doughnut) (ring-shaped) patterned injury consisting of two opposing (facing) symmetrical, U-shaped arches separated at their bases by open spaces. Following the periphery of the arches are a series of individual abrasions, contusions and/or lacerations reflecting the size, shape, arrangement and distribution of the class characteristics of the contacting surfaces of the human dentition. Variations of the Prototypical Bitemark Variations include additions, subtractions and distortions.
COMMENT: This list excludes variations caused by individual characteristics of the biter’s teeth. Unique This term is variably defined as either one of a kind or rare and unusual. In its most conservative interpretation the following connotations apply:
To those who use a more liberal interpretation the following would apply:
COMMENT: Forensic odontologists should specify their meaning when they use the word unique. Distinctive
COMMENT: A consensus of odontologists indicated that in the hierarchy of the terminology, "unique" implies greater rarity than "distinctive". back to ABFO Bite Mark Guidelines Terms Indicating Degree of Confidence That an Injury is a Bitemark Possible Bitemark: An injury showing a pattern that may or may not be caused by teeth; could e caused by other factors but biting cannot be ruled out.
Probable Bitemark: The pattern strongly suggests or supports origin from teeth but could conceivably be caused by something else.
Definite Bitemark: There is no reasonable doubt that teeth created the pattern; other possibilities were considered and excluded.
COMMENT: These terms are opinions, representing 3 zones of confidence and do not convey a statistical or mathematical measurement of precision. A lesser quality bitemark can be elevated to definite if multiple bitemarks are present or if amylase is positive. Terms to indicate that an injury represents a bitemark Ordinate Ranking of Terms Connotation
COMMENT: The above ranked terms are to define the injury itself as opposed to the terms used to describe the degree of certainty that a particular set of teeth caused the wound. Please refer to the "Terms to indicate the Link Between Bitemark and the Suspect(s)" for acceptable terms used to describe the comparison opinion. back to ABFO Bite Mark Guidelines Descriptions and Terms Used to Link a Bitemark to a Suspect A Point, Concordant Point, Area of Comparison, Match, Consistent Point:
COMMENT: This term is used as a convenience in reports to address specific components of the bitemark which are being compared to teeth. A point doesn’t imply any degree of specificity and not a characteristic. Concordant Point:
Area of Comparison:
Match:
COMMENT: This term "match" or "positive match" should not be used as a definitive expression of an opinion in a Bitemark case. The statement "It is a positive match" or "It is my opinion that the bitemark matches the suspect’s teeth" will likely be interpreted by juries as tantamount to specific perpetrator identification when all the odontologist might mean is that a poorly-defined or nonspecific bitemark was generally similar to the suspect’s teeth, as it might to a large percentage of the population. Consistent (compatible) With:
COMMENT: If used to represent the odontologist’s conclusion, the term "consistent with" should be explained in the report or testimony as indicating similarity but implying no degree of specificity to the match. This is necessitated by the fact that our survey showed that this term varied in meaning among odontologists to indicate everything from " possible" to "absolute certainty"; its message is unreliable. However, when used as proposed, it is an acceptable term for those odontologists who are reluctant to suggest culpability of a suspect. Possible Biter:
Criteria: there is a nonspecific similarity or a similarity of class characteristics; match points are general and/or few, and there are no incompatible inconsistencies that would serve to exclude. COMMENT: This term is approximately synonymous with "consistent with" but has a more universally understandable meaning. Probable Biter:
Criteria: bitemark shows some degree of specificity to the individual suspect’s teeth by virtue of a sufficient number of concordant points including some corresponding individual characteristics. There is an absence of any unexplainable discrepancies. Reasonable Medical Certainty:
Criteria: there is a concordance of sufficient distinctive, individual characteristics to confer (virtual) uniqueness within the population under consideration. There is absence of any unexplainable discrepancies. COMMENT: The term reasonable medical certainty conveys the connotation of virtual certainty or beyond reasonable doubt. The term deliberately avoids the message of unconditional certainty only in deference to the scientific maxim that one can never be absolutely positive unless everyone in the world was examined or the expert was an eye witness. The Board considers that a statement of absolute certainty such as "indeed, without a doubt", is unprovable and reckless. Reasonable medical certainty represents the highest order of confidence in a comparison. It is, however, acceptable to state that there is "no doubt in my mind" or "in my opinion, the suspect is the biter" when such statements are prompted in testimony. back to ABFO Bite Mark Guidelines Degrees of Certainty Describing The Link Between the Bitemark and Suspect Terms Connotation
COMMENT: Using numbers and percentages to represent opinions is inappropriate unless a specific statistical analysis on a case has been done. back to ABFO Bite Mark Guidelines ABFO Standards for "Bitemark Terminology" The following list of Bitemark Terminology Standards have been accepted by the American Board of Forensic Odontology.
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A Famous Bite Mark Case Reviewed
This is the Florida bite mark case you might know as People v. Bundy. The overlays are hand drawn. |