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
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
Ted Bundy Bite Mark Case
Arguments on the Individuality of Teeth
The Torgerson Case
The Detection and Analysis of Photographic and Anatomical Distortion
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
ABFO Bite Mark Guidelines
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.
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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.
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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 theJournal 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.
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Dentists testify in court regarding certain types of medical evidence involving teeth. The basis of many bitemark opinions is the direct superimposition of Questioned and Known sample photographs that have sufficient identification value to demonstrate features of common origin or establish an exclusionary result. These direct analysis methods all demand rigorous attention to scale dimensions and the detection of photographic distortion in these images of forensic interest. The dental techniques are generally analogous to the physical comparison of Q and K evidence in fingerprint, ballistics and toolmark studies. These disciplines have the criminalist using a comparison microscope to place the Q and K evidence samples side by side. The loops, whorls, striations, indentations, accidental, and class characteristics present in the evidence samples may then be visually compared. What is difficult to assess, however, in both the crime lab and the dental lab, are the dimensional parameters of the evidence samples. In dentistry, the traditional ruler and protractor measurements and shape comparison processes are manually derived from evidence photographs and plaster models of a suspectís teeth. These methods can vary between examiners. Alternatively, some crime lab analysts ignore size comparisons and focus on similarities in class and individual features. In both situations, the possibility of error arises from examiner-subjective methods and partial selection of the available physical information.
The recent development of easily available digital imaging software and image capture devices such as scanners and digital cameras has created an opportunity to better control these well-recognized variables and allows the forensic examiner to turn the computer monitor into a comparison microscope with the added benefit of the following functions:
The steps necessary to create a digital comparison are described in this section.
The examples are from a typical forensic dentistry evaluation of bitemark evidence and dental identification of unidentified remains. The application of these methods may also be useful to other areas of forensic investigation that require image comparison information.
Features of Digital Evidence
There are a number of formats in which forensic investigators receive two-dimensional bite-mark evidence. These include floppy disks, zipped (compressed) computer files, Zip Disks (100MB or 250 MB storage capacity) , compact disks (CD), email attachments, and most often photographic prints, slide or negatives.
The detail of a digital image is represented by the number of dots per inch (dpi) for scanners and digital cameras. Computer printers output these images in lines-per-inch (lpi). The computer storage necessary to store a photographic quality, 8 Ĺ " x 11" picture is over 20 Megabytes when 300 dpi is the selected resolution.
Storage of Archival Images
Digital imaging demands that the examiner document each original image and create a duplicate image for later use as a working copy.
Zoom settings on the computer monitor
Adobe Photoshop is a popular software program which allows for a multitude of imaging features, functions, enhancements and metric analysis. The initial working image can be enlarged using the Zoom tool. Increments of 25% up to 300 and 400% enlargements may be shown on the computer monitor using this tool. The only limitation is the very high resolution image (300 dpi required to avoid pixellation (fuzziness) of the magnified picture.
The tools within Photoshop can be used to detect and correct for certain angular distortions. This is an extremely important step as it forms the foundation for the comparison procedures that follow. The first issue with this picture is the scale's off-angle position relative to the bitemark.
Figure One:Angular Distortion
A photograph is a graphical representation of the objects with the range of the cameraís lens. The degree to which this graphic exactly reproduces those objects is influenced by many variables. When bitemarks are photographed or dental xrays are used as evidence, attempts are made to carefully control perspective variables in an effort to obtain an accurate representation of the bite mark or dental restoration for later comparative analysis. Unfortunately, these efforts are not always successful and distortion is often introduced into the image.
Photography of bitemarks and similar types of two and three-dimensional physical evidence should have the following features:
Correction for angular distortion focuses on the size and shape of the ruler present in the image. The sides of the scale or ruler must be parallel, the incremental lines perpendicular to these sides and equally spaced, and, if present, any circular reference shapes must be round (not oval). A two-legged scale (actually a two dimensional scale possessing a x,y axis) will have a 90 degree angle created at the intersection of the two legs. An ABFO #2 (Lightning Powder Co.,Inc., Salem Oregon) scale is used in the figures for this chapter.
Placing A Grid on the Image
The degree of distortion can be preliminarily checked by placing a digital circle over the circular reference target and using it to evaluate the scalesís sides, incremental lines, and angles for parallelism. In this case the corner of the "L shaped" ruler was in the same plane as the injury pattern and later this could be used to establish the life-size dimensions of the picture. I used 1.5 centimeters of the ruler to accomplish this.
Figure Two: Digitally Created Circle Placed in Corner of "L" Shaped Ruler and Red Box Showing Undistorted Length of Scale.
Simple Rotation and Cropping of the Bite Mark Image
The evidence image must have the scale oriented along the x/y axis of the entire image in order to perform later manipulation based on this scale.
Excess perimeters in the image may be removed using the Crop tool.
Figure Three: Cropped and Scale Rotated to the proper x,y axis.
Determination of Theta
The next step in evaluating the bite mark photograph is to refer to the circular reference shapes present on the scale. (Using the digital circle as a guideline).
An elliptical shape proves the camera angle was incorrect. The angular amount of non-parallelism is determined by:
The angle Theta may be determined by solving Theta = COS-1 A/B
Placement of Perfect Circles Over Scale
A non-metric method for detection of angular distortion is to visually compare the reference shapes of the scale with a perfect circle. (As seen above in Figure Two).
Correcting for Photographic Distortion
If it has been determined that significant distortion exists, it must be corrected before the bite mark photograph is resized and/or enhanced. Only then can a meaningful comparison analysis be accomplished.
Type I Distortion
The scale and bite mark on plane but camera back is not parallel to either.
This non-parallelism of the camera can be corrected.
When the image of the scale is brought back to its original size and shape, the image of the bite mark will also be corrected (rectification). This assumes that the scale itself is on a single plane and there is no parallax distortion relative to the bite mark.
Type II Distortion
If the scale is not on the same plane as the bite mark, rectifying the scale will adversely affect the proportions of the injury pattern. In situations like this it is best not to try to rectify the scale but do the later resize ( 1:1) procedure based on the scale "as is."
The amount of parallax distortion present will obviously affect the accuracy of the results. The weight given to the results will contribute to the ultimate decision in the case. The investigator must decide what amount of distortion is acceptable in order to produce a meaningful comparison
Type III Distortion
In some cases, one leg of a two-dimensional scale will have perspective distortion but the other leg will not
Notice in this illustration, the vertical of the scale is distorted but the horizontal leg is not. Here, we can use the non-distorted leg to do the resizing procedures with good results. This would be similar to performing a resize based on a one-dimensional scale (i.e., a straight ruler) in the image.
Type IV Distortion
In this instance, the scale itself may be bent or skewed.
Look at the scale and decide if this type of distortion is present. There can be forensic value if the scale is relatively flat in the area directly adjacent to the bite mark. Peripheral scale inaccuracies can be discounted. Use only the area next to the mark for the resizing procedures. Do not use the entire scale. There must be at least a 5 cm. Length of no-distorted scale in close proximity to the bite mark.
Application to other two and three-dimensional objects.
The above scenarios encompass most of the physical distortion seen in bite mark and other evidentiary photographs. When detected and properly corrected, the resulting image modification will result in an accurate resize and a meaningful comparison.
Limitations to this method
There are cases in which the image is so severely distorted, due to poor photographic technique, that it is of no use. The subject matter must be re-photographed. Unfortunately sometimes physical evidence is transitory, fragile, or evanescent in nature, thus preventing these remedial efforts.
It is important to realize which type of distortion, if any, is present within the original bite mark photograph. This can often be a difficult task and requires some experience. Also of concern is the fact that we are asking a two-dimensional object (the scale) help us analyze a three-dimensional bite mark. In some instances, this is not a big problem. For example, if the bite mark is on a relatively flat surface. Other times, with a bite mark on a very curved surface, it is a very significant concern.
The final analysis of each case depends upon the quality of the evidence presented. In cases where all the variables are carefully controlled and little distortion exists, greater certainty of opinion is possible than if the quality of the evidence is weak. In come case the quality of the bite mark photograph may be so poor that it precludes a meaningful analysis altogether.
The variations present in bite mark cases present challenges to the examiner regarding the value of the injury pattern and the relationship to a suspect(s) teeth. Photoshop can help in a large number of these cases but, again, it is up to the investigator to understand how much distortion is significant, how it affects the analysis and its impact on the strength of the ultimate opinion.
This should emphasize the need to follow strict protocol and use a tripod whenever possible when photographing bite mark injuries and other types of physical evidence
A. Simple overlay
A major purpose of using digital imaging in the analysis of a suspectís dental evidence is to produce a properly rectified, scaled, reproduction of the teethís biting edges. The term Hollow Volume refers to the outline or perimeter of each biting surface. This product is called an overlay. The final process is to place the overlay onto the bite mark evidence and evaluate the physical correspondence between the two. The increased accuracy of this digital process is the chief improvement over the conventional methods of overlay production. The dental examiner uses the computer program to select the biting edges, rather than having to hand draw them directly from the plaster models of the suspectís teeth.
Figure Four: Scan of dental models. If you look real closely, the outline of the front teeth have been selected as a black outline.
From this selection of the biting edges of the teeth, their outline is used to produce the computer-generated overlay.
Figure Five: Computer Generated Hollow Volume Overlay
You will notice that the upper curve of teeth do not rest on top of anything visible in this bitemark. The evidence picture did not contain any discernible upper teeth present in the injury.
The actual computer comparison uses each dental arch (upper and lower) separately. This is because the examiner's scan of the dental casts has the relationship of the upper and lower teeth just set arbitrarily on the scanner plate. This position on the scanner plate does not reproduce the actual upper and lower jaw relationship of the suspect.
Figure Six: Digital Comparison
The use of digital imaging allows the examiner to establish physical data parameters for bite mark cases. The application of certain of Photoshopís tools and functions will provide the dental examiner with concise physical evidence data that will create linear and angular information useful to support the final conclusions regarding a case.
Bite mark injuries AND suspect(s) teeth possess pertinent physical characteristics which are amenable to digital measurement. The most obvious are:
Step One: Analysis of Bite Mark Injury
It is recommended that the injury pattern be completely analyzed before the dentition of a suspect(s) is evaluated. This insures a measure of blindedness when features of the injury are vague and ambiguous. This establishes hard data sets for this Questioned sample before commencing the analysis of the suspectís teeth.
Figure Seven:Typical Metric and Spatial Analysis of Bite Mark (Data Points Placed at Central Portion of Each Mark in Injury. Teeth #8 and #9 are not clearly seen in bite mark and are not included. Tooth # 5 has the data point placed in its central fossa. )
Step Two: Analyzing the Suspect Dentition
Identical steps are then performed using the scanned images of the suspectís plaster dental casts.
Metric Analysis of Dentition Casts using the following features of each tooth.
Step Three: Comparison Data of Hypothetical Case (only two features noted in this example))
Bitemark: Upper Jaw Distance
Cuspid to cuspid
Suspect; Upper Jaw Distance
Cuspid to cuspid
Tooth 6 to Tooth 10
Angle: + 14.5 Degrees
Angle: + 12.52 Degrees
Figure eight: A very mean dog made this bite, Thanks to Dr. Gary L. Bell for this picture.
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Bite mark Standards and Guidelines
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©American Board of Forensic Odontology
ABFO BitemarkTerminology Guidelines
Collection of Bitemark Evidence from Suspect
Collection of Evidence from Victim
Certainty of Bitemark Diagnosis
Degrees of Certainty
Evaluation of Bitemark Evidence
How to Describe a Bitemark
Methods to Preserve Bitemark Evidence
Standards for Analytical Methods
Report Writing of Bitemark Evidence
In 1993, the ABFO Bitemark Workshop #2 Committee distributed a questionnaire on Bitemark methodology. About half of our members responded to the Bitemark Methodology survey reviewed at the three day Bitemark Workshop in San Antonio on February 12-14, 1994. The methods used by those that responded to collect and analyze Bitemark evidence were presented. This project is an update of the efforts begun in the 1984 Bitemark workshop. This set of guidelines is not intended to invalidate the document generated as a result of the 1984 workshop.
Please read Bitemark Methodology with the following perspective:
There is a need for forensic dentists to agree on basic methodology used in bitemark cases so as to maximize the quality, completeness and validity of the collection and analysis of bitemark evidence. It is not expected that this document is ideal to all forensic dentists. However, it represents majority opinions and has the highest level of acceptance to the largest number of odontologists. All Diplomates (and other forensic odontologists) will have to make some compromises if the science of forensic odontology is to achieve the higher objective of universally agreeable methodology. There is no intention for the ABFO to mandate methods but instead to provide a list of generally accepted valid methods for this point in the development of our science. This document is not meant to stifle the development of new valid techniques that meet the criteria of the scientific method. There is every intention for the ABFO, as a credible body of experts, to present a clear and unified message as to what its members use and accept as valid methods for the collection and analysis of bitemark evidence. This document will present methods that have been agreed upon and approved as valid preservation and analysis procedures. In keeping with the commitment not to stifle the development of new methods, individuals should continue to develop new and possibly better techniques. These new techniques should be backed up by the use of accepted techniques and should satisfy the basic concepts of the scientific method.
General Considerations - It should be recognized that often the Forensic Odontologist is not involved in the initial examination and collection of the Bitemark evidence. This does not necessarily preclude the ability of the Forensic Odontologist to render a valid opinion. The below listed methods are not meant to be an all encompassing list of preservation methods; however, it does list those methods that are used by the Diplomates of the ABFO. The use of other methods of documenting the Bitemark evidence should be in addition to these techniques.
2. Evidence Collection of Suspected Dentition
A 1994 survey of Diplomates of the American Board of Forensic Odontology indicated that they presently use the following analytic methods in the comparison of Bitemark evidence.
Bitemark Analysis Guidelines
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.
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
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:
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
If all teeth that can be individually identified in the bitemark are also present in the suspectís 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 suspectís 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 ó 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.
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 suspectís 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.
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 suspectís 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
Features Analyzed Nbr. of Points Max. Mand. Discrepancy
All teeth in mark present in suspectís 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 and tooth mark in same
labiolingual position *One per tooth
Tooth and mark in same
(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
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
Suspect has one edentulous arch and this is reflected in bite mark Three
Total, each arch:
*Three points if feature is significantly distinctive.
**Only in case permitting accurate measurement.
2/20/84 Committee on Bite Mark Guidelines
back to ABFO Bite Mark Guidelines
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.
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.
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.
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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 biterís teeth.
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.
COMMENT: A consensus of odontologists indicated that in the hierarchy of the terminology, "unique" implies greater rarity than "distinctive".
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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.
The pattern strongly suggests or supports origin from teeth but could conceivably be caused by something else.
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.
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.
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A Point, Concordant Point, Area of Comparison, Match, Consistent
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 doesnít imply any degree of specificity and not a characteristic.
Area of Comparison:
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 suspectís 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 suspectís teeth, as it might to a large percentage of the population.
Consistent (compatible) With:
COMMENT: If used to represent the odontologistís 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.
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.
Criteria: bitemark shows some degree of specificity to the individual suspectís 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.
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COMMENT: Using numbers and percentages to represent opinions is inappropriate unless a specific statistical analysis on a case has been done.
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The following list of Bitemark Terminology Standards have been accepted by the American Board of Forensic Odontology.
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.