|FORENSIC ODONTOLOGY: ORIGINAL ARTICLE
|Year : 2018 | Volume
| Issue : 1 | Page : 58-63
Human bite marks – A computer-based analysis using adobe photoshop
Lalitha Chintala1, Marthala Manjula2, Stuti Goyal3, Vinil Chaitanya1, Md K A. Hussain4, YC Chaitanya1
1 Department of Oral Medicine and Radiology, Malla Reddy Institute of Dental Sciences, Hyderabad, Telangana, India
2 Department of Oral Medicine and Radiology, Government Dental College, Vijayawada, Andhra Pradesh, India
3 Department of Oral Medicine and Radiology, Srinivasa Institute of Dental Sciences, Mangaluru, Karnataka, India
4 Department of Oral Medicine and Radiology, B.R. Ambedkar Dental College, Patna, Bihar, India
|Date of Submission||21-Sep-2017|
|Date of Acceptance||06-Mar-2018|
|Date of Web Publication||23-Apr-2018|
Dr. Lalitha Chintala
H. No: 11-142, Lakshmi Residency, Flat No. 203, Sahithi Nagar, Gaddi Annaram, Dilsukh Nagar, Hyderabad - 500 060, Telangana
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Aim: Identification of human bite marks on victims and to analyze them by computer-based superimposition technique using Adobe Photoshop software. Materials and Methods: Five bite mark cases were selected for this study. Five bite marks were identified on patients attending the hospital and were analyzed with computer-based superimposition technique using Adobe Photoshop software by two observers. Results: All the five bite marks on victims were analyzed by computer-based superimposition technique using Adobe Photoshop software and categorized as “not excluded as having made the bite mark with suspects dentition.” Conclusion: Computer-based superimposition technique using Adobe Photoshop software is an accurate and cost-effective method for bite mark analysis.
Keywords: Adobe Photoshop, human bite marks, overlay
|How to cite this article:|
Chintala L, Manjula M, Goyal S, Chaitanya V, A. Hussain MK, Chaitanya Y C. Human bite marks – A computer-based analysis using adobe photoshop. J Indian Acad Oral Med Radiol 2018;30:58-63
|How to cite this URL:|
Chintala L, Manjula M, Goyal S, Chaitanya V, A. Hussain MK, Chaitanya Y C. Human bite marks – A computer-based analysis using adobe photoshop. J Indian Acad Oral Med Radiol [serial online] 2018 [cited 2021 Nov 30];30:58-63. Available from: https://www.jiaomr.in/text.asp?2018/30/1/58/230899
| Introduction|| |
“Forensic odontology,” has been defined by Federation Dentaire International as “that branch of dentistry which, in the interest of justice, deals with the proper handling and examination of dental evidence, and with the proper evaluation and presentation of dental evidence.” The most complex and controversial challenge in forensic dentistry is the recognition, recovery, and analysis of bite marks. Bite marks can be found on tissues, food, and intimate materials. They can be of human or animal origin. Human bite marks may be associated with assault, homicide, child abuse, and or sexual assaults. Females are most often bitten on the breasts, arms, and legs during sexual attacks, whereas bites on males are commonly seen on the arms and shoulders. In defensive circumstances, as when the arms are held up to ward off an attacker, the arms and hands are often bitten.
When bite marks are involved in homosexual homicides, they tend to be on the back, arms, shoulders, face, and scrotum of the victim. Breast and thigh marks indicate heterosexual aggression and tend to be done slowly and sadistically, which leaves an excellent impression. Battered children have randomly placed bite marks that are generally diffuse and of poor detail.
Human dentition is unique because no two individuals have identical dentition with regard to the size, shape, and alignment. Bite marks are now accepted as evidence in courts of law. Life-and-death decisions can hinge upon the accuracy with which such evidence is interpreted. Courts have admitted evidence in different types of cases. No reported case has yet been rejected as bite mark evidence. Its acceptance is so well-established that its validity need not to be proved in every case.
The aim of this study was to identify and analyze human bite marks by computer-based superimposition technique using Adobe Photoshop software.
| Materials and Methods|| |
Five cases were selected for this study. These cases were selected from the patients attending Dental OP, at Government Dental College and Hospital, Hyderabad, Casualty of Osmania General Hospital, and autopsy bodies at Forensic Department of Osmania Medical College, Hyderabad. Cases where bite marks are clearly visible on the body are included in the study. Bite marks on food stuff, other objects, and animal bite marks were excluded from the study. Patients and bodies were examined thoroughly. Details of the suspects were also taken, and questioning regarding the crime was recorded. Particulars were noted in a specially prepared proforma. Bite mark analysis was carried out after taking permission from concerned authorities. Bite mark analysis was done with computer-based superimposition technique using Adobe Photoshop software by comparing each bite mark with five overlays by two different observers.
Bite mark analysis was carried out in the following three steps:
- Identification of bite mark
- Evidence collection
- Analysis of bite marks using Adobe Photoshop
Identification of bite mark
(a) On victim: Identification of the bite mark is a crucial step in bite mark analysis. Many times bite marks go unnoticed by medical, dental, and other healthcare providers as well as criminal investigators during clinical examination or during autopsy. Demographic information, that is, name, age, sex, and race, were obtained in cases of both living and deceased victims. Asking probing questions to the victim about the behavior of perpetrator is stressful; keeping in mind that not only physical injuries but also mental abuse and intimidation are a part of abuse, careful history from the victim was taken. Permission was sought to photograph suspicious injuries. Bite mark injuries were documented.
Both the victim and the suspect were examined, and evidence from each was gathered for comparative study and evaluation.
(a) Examination of bite marks: The bite marks were visually examined and the following details were documented according to American Board of Forensic Odontology (ABFO) guidelines:
- Anatomical location of bite mark or object and tissue characteristics
- Type of injury (abrasion, laceration, ecchymosis, and petechial hemorrhage)
- Physical appearance (color, size), orientation
- Bitten surface contour (e.g., flat, curved, or irregular), texture, and elasticity of the bite site
- Differences between upper and lower arches and between individual teeth
- Identification features within a bite mark-like rotations, translations, or other anomalies of teeth.
(b) Photography of the bite marks: Bite marks present on the victim were documented by photographs with the use of scale and Sony cyber shot camera with 12.1 megapixel and 5 optical zoom. Photographs of bite marks were taken using the following instructions:
- The presence of scale is oriented on the same plane as the bite mark or evidence sample
- The orientation of the camera back (film plane) to the scale is parallel.
(c) Evidence collection from the suspect: A standard case history and informed consent were obtained before any evidence recovery procedure from the suspect. An intraoral and extraoral examination of the suspect is completed. After detailed clinical examination, the following evidences were collected from the suspect:
- Photographs of the suspect's teeth
- Maxillary and mandibular impressions were made with alginate impression material, followed by cast pouring with dental stone.
Analysis of bite marks using Adobe Photoshop
- Scanning the bite mark: Photograph of the bite mark was scanned and resized to a life-size photograph using Adobe Photoshop software. The impressions of the subject's dentition were obtained, and the casts were poured. Two coats of cold mould seal (separating media) were applied to the casts using a thin-haired brush. After the separating media were dried, the casts were pressed with moderate pressure, into stamp pad such that the plane of occlusion was parallel to the surface of the ink pad to select the incisal edges. Then the cast was scanned along with the ABFO No. 2 scale placed beside it. The scanned image was then transferred to Adobe Photoshop. The Magic wand tool cursor was clicked on the blue colored inked incisal edges of the teeth. The Magic wand tool selects an area of similar pixel tone. To add to the selected area of a tooth or to select additional teeth, the Shift key was held down while making additional selections. Thus, keeping the Shift key pressed, the blue colored inked incisal edges of the rest of the teeth were also selected. In this way, all the incisal edges of the six teeth were selected and were subsequently smoothed
- Construction of the overlay:Since the overlay will be on a layer separated from the Background, a new layer was created. The selected edges were outlined by clicking Edit > Stroke > Stroke dialog box > Stroke width > 1, Location > Inside > OK > Ctrl + D
- Nonmetric analysis of the bite mark and suspect's dentition: When the bite mark image and the overlay are completed, a nonmetric analysis was carried out. This analysis involves superimposing the overlay onto the bite mark injury and investigating points of concordance or discrepancy. A typical bite mark comparison image includes the bite mark image as the background layer, the maxillary arch overlay layer, and a mandibular overlay layer. Each of these layers can be enhanced or moved individually.
| Results|| |
Based on the gross, class, and individual features [Table 1], overlays of teeth of the perpetrator were matched with the bite mark on the skin of the victims. For each bite mark, all the five overlays were tried and interpreted by two different observers.
The first case was that of sexual assault on a 70-year-old female victim. Bite marks were found on her breast, right pubic area, and back. Bite marks on the breast and back were not significant. Bite mark on the pubic area was quite significant. It was roughly circular in shape and there were two teeth marks of the upper arch and two of the lower arch, and they were rectangular in shape. There were central and peripheral suck marks present indicating that it was a sexual assault. There were no teeth marks present on the left side in the upper arch on the bite mark. On clinical examination of the suspect, many teeth were missing 11, 12, 13, 14, 15, 16, 17, 24, 31, 34, 36. Numbers 22 and 25 were supra erupted. No. 25 was mesially drifted and it was slightly rotated. Numbers 32 and 33 were also mesially drifted. Overlays of the scanned casts were compared with the bite mark photograph. No. 22 and rotated 25 which were supra erupted, and 32 and 41 were matched with the bite mark.
The second case was that of domestic violence. The victim was bitten by the suspect. Bite marks were found on the right arm of the victim [Figure 1]. The photographs were taken 2 days after the injury showing crust formation. At the site of bite, there were multiple bite marks present resulting in slight overlap of the bite marks. The bite marks were found on the curved surface and they were roughly circular in shape. Four teeth marks of the upper arch with rectangular shape represent incisors. Three teeth marks were seen in the lower arch, one pointed in the center and two were triangular in shape representing canines. On clinical examination of the suspect's teeth, there was full complement of teeth present with spacing between 11, 12 and 21, 22. [Figure 2] and [Figure 3] Mesio incisal edges of 31 and 41 were slightly lingually rotated. Dental caries of 15 and 26 were seen. Overlays of the scanned casts were compared with the bite mark photographs of 11, 12, 21, 33, 43 and mesioincisal edges of 31 and 41 coincided with the bite mark [Figure 4] and [Figure 5].
|Figure 2: Suspects' maxillary arch with spacing between 11, 12 and 21, 22|
Click here to view
In the third case, a 2½-year-old female patient has bitten a BDS student while taking an IOPA radiograph. Bite mark was present on the palmar surface of left-hand index finger. Bite mark was caused by the mandibular teeth. There were two teeth marks present which were rectangular in shape suggesting incisors. On clinical examination of the suspect's teeth all the teeth were deciduous. Overlays of the scanned casts were compared with the bite mark photographs; 31 and 32 coincided with the bite mark.
In the fourth case, the victim has bitten himself on his forearm in anger. Bite mark was roughly circular in shape. Four teeth marks in the upper arch which were rectangular in shape represent incisors. Five teeth marks of the lower arch were present, in that four were rectangular indicting incisors and one was triangular indicating canine. On clinical examination of the victim's teeth, full complement of the teeth was present. Lower arch crowding was seen. Overlays of the scanned casts were compared with bite mark photograph; 11, 12, 21, 22 and 31, 32, 41, 42, 43 coincided with the bite mark.
In the fifth case, the perpetrator has bitten the victim in anger during a fight. Photographs were taken after 1 day. As the post mortem changes have already started, the body was swollen making bite mark analysis difficult. Bite marks were found on the abdomen region. The mark was oval in shape and the teeth marks resembled ecchymotic marks. Teeth marks were slightly dragged; six teeth marks of the upper arch and six teeth marks of the lower arch were seen. On clinical examination of the suspect, all teeth up to second molars were present. No. 12 was placed slightly labially. Mandibular anterior teeth crowding was seen. Overlays of the scanned casts were compared with the bite mark photographs; 11, 12, 13, 21, 22, 23 and 31, 32, 33, 41, 42, 43 coincided with the bite mark.
All the cases were examined by two observers separately by comparing all five bite mark overlays and it was analyzed by computer-based superimposition technique using Adobe Photoshop. According to ABFO bite mark methodology standards and guidelines, all the five cases were categorized under “not excluded as having made the bite mark” [Figure 6].
| Discussion|| |
It has long been recognized that bite marks are unique , and can be attributed to specific individuals. A study in 1991 has established dental uniqueness beyond a reasonable doubt. Even the dentition of identical twins is not identical. It has been estimated that in about 2.5 billion people, there may be two persons who produce identical bite marks. This means that in India, with a population of 1 billion, no two persons will have identical bite marks.
Mac Donald defined bite mark as “a representative pattern left in an object or tissue by the dental structures, either alone or in combination with other oral structures of an animal or human.” Bite marks may be caused by humans or animals. They may be on tissue, food items, or other objects. Many forensic odontologists classified bite marks according to Cameron and Sims classification, Mac Donald's classification, and Webster's classification.
The terms commonly used in bite mark analysis are as follows:
- Victim –the recipient of the bite mark
- Perpetrator – the person who caused the bite mark
Vernon Gaberth  in practical homicide investigation points out that homosexual homicides, when they have bite marks involved, tend to have them on the back, arms, shoulders, face, and scrotum of the victim. Breast and thigh marks indicate heterosexual aggression and tend to be done slowly and sadistically, which leaves an excellent impression. Battered children have randomly placed bite marks that are generally diffuse and of poor detail. Human bite marks are most often found on the skin of the victims and they may be found on almost all parts of the human body. Female are most often bitten on the breasts, arms, and legs during sexual attacks (e.g., first case), whereas bites on males are commonly seen on the arms and shoulders (e.g., fifth case; third case). In defensive circumstances, as when the arms are held up to ward off an attacker, the arms and hands are often bitten.
Wood et al. in their study of a bite mark analysis of a sexual assault case have used radiographic, xeroradiographic, and computer-based technique. They stated that among the three methods, radiographic and xeroradiographic methods lack accurate details. They were able to match accurately with computer-based method. This study was done on five cases, and all the cases were matched which shows that the computer-based method is more accurate when compared to other methods.
Whittaker DK  conducted a study on 84 bite mark cases. Bite marks were voluntarily created on wax and pig skin. Comparison was done based on a visual method depending on arch curvature, width of teeth, angulations of teeth, and spacings between teeth. Only 68% cases were matched, and they stated that visual matching using subjective criteria is less accurate. This study uses computer-based method which is more objective in nature and the results were statistically significant (96%). National survey of the incidence of missing anterior teeth conducted by Lopez et al. stated that missing teeth act as a potential useful tool in the bite mark analysis. Similarly, in this study in one case (e.g., first case), the suspect had missing teeth which helped in bite mark analysis.
According to Rawson et al., a curved body surface which allows visualization of the entire bite mark has a small amount of photographic distortion similar to one case (second case) though the bite mark was found on the curved surface, that is, on the right arm, suspects teeth were matched with the bite mark. This is because the visualization of entire bite mark has a surface angle that was too small to produce significant photographic distortion.
Sweet et al. described computer-based method and they used this method on a number of cases involving human bites on skin and they stated this to be an accurate method. In this, five cases of bite marks on skin were compared with the suspects' teeth; using this method among them five cases were matched. The results indicate that the computer-based method is an accurate method and also indicates that human teeth and bite marks they create are indeed unique.
Previously, many authors tried to fabricate overlays of suspect's teeth by various methods such as photographic, wax imprint, radiographic, and xeroradiographic. The disadvantage of these methods was that they are more subjective in nature. This study uses computer-based method which is more objective when compared to the other methods. The computer-based method uses Adobe Photoshop software in which various tools digitally select the incisal edges of the teeth and fabricate overlays.
These overlays can be easily compared with the life-size image of the bite mark. Another advantage of this method is the reproducibility. This method reduces examiner variability and also reduces human errors. This study was carried out based on a nonmetric method, but in future metric analysis and 3D bite mark analyses  may be used to be more precise.
| Conclusion|| |
Bite marks are usually associated with sex crimes, violent fights, child abuse, and thefts. If the teeth leave definitive marks, it should be possible to individualize them to a particular person. Hence, matching the bite mark to a suspect's dentition may enable law to implicate the suspect in the crime. Bite marks on the skin, food stuff, or on any other material can be considered as a type of physical evidence and it has an evidentiary value in court of law. This study was done on identification and analysis of human bite marks by computer -based superimposition technique using Adobe Photoshop software. This method is easy and cost-effective and gives reproducible results.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]