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Title: Forensic dentistry : bite mark distortion
Author: Sheasby, Douglas Robert
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1998
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Abstract:
The major challenge in forensic dentistry is the analysis of bite marks in human skin. A recurring difficulty in analysis arises from the distortion which is a variable feature of bite marks. Distortion may complicate or even preclude proper comparison of the bite mark and the causal dentition. Distortion may arise in a number of ways. The action of biting may produce tissue distortion and dynamic distortion. Evidence recording of the bite mark may produce posture distortion and photographic distortion. Ante and post mortem changes may also introduce distortion. The present research initially consisted of a retrospective review of forensic bite mark cases analysed in Glasgow between 1971 and 1989. The review, reported in Chapter 2, demonstrated that the breast was the most commonly bitten anatomical location in females and that the quality of recording of individual tooth elements in the bite marks was variable; good quality elements formed the minority group. Experimental research of human bite marks in human skin is, by its nature, difficult to conduct. Consequently, previous studies have mainly used experimental bite marks in animal skin or experimental bite marks in artificial media. One study in America recorded bite marks accurately in wax and established criteria which would require to be satisfied in bite mark cases. The retrospective review of bite mark cases found that bite marks which demonstrated good quality individual tooth elements formed the minority group and consequently the requirements for valid comparisons set by the American research were infrequently met in case work. A particular forensic bite mark case in Liverpool demonstrated distortion of a bite mark in the female breast; the posture distortion was produced by varying the victim's arm position during evidence recording. The posture distortion percentage values were of the order of 25%. This case provided the stimulus to research posture distortion in the female breast. In addition, the relevance of the female breast as an anatomical site for study had been established in the retrospective review. A preliminary study of two subjects was undertaken to quantify posture distortion in the female breast, to compare posture distortion in different breast sites and to study the influence of arm movement on posture distortion. The preliminary study is described in Chapter 3. As an alternative to experimental bites, a die stamp was designed with approximate dimensions of a human bite. Marks were made on different areas on the breast with the subject's arm in several positions. Dimensional changes were measured and expressed as percentage changes. The posture distortion percentage values of the preliminary study were similar to those in the Liverpool case. Therefore, the preliminary study was assessed as realistic in demonstrating posture distortion comparable to that in a forensic bite mark case. The preliminary study produced general conclusions which provided the basis for further research. The initial stages of the main study, reported in Chapter 4, of 20 subjects of varying ages and anatomical proportions was undertaken to quantify posture distortion in the female breast, to compare posture distortion in multiple axes of four breast sites and to study the influence of arm movement on posture distortion. In addition, the main study assessed the influence of age, bust size, cup size and ptosis on posture distortion, The dimensions of the marks were recorded photographically and defined elements of the marks were digitised manually for computer analysis. The study showed that maximum posture distortion was mainly related to older subjects with increased ptosis and a larger cup size. In view of the large volume of data, it was considered appropriate to concentrate initially on certain measurements from the left breast. The longest measurements in each axis reflected the major dimensions encountered in bite mark cases. In this way the main study produced six measurement tables of data. The analyses of the six sets of measurements are presented in Chapters 5, 6, 7 and 8. The main study researched posture distortion in the female breast. Clearly, the technique could be applied to other relevant anatomical sites which are potentially liable to posture distortion. In this way, a scientific database of posture distortion values and significant factors would be created.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (D.D.S.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.788710  DOI: Not available
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