咬痕及其法医学鉴定

咬痕(bite mark)是指某一个体的牙齿或牙齿与口腔其它部分一起作用于物体(人体、食物和其它物体),造成该物体在形态学上发生改变而留下的痕迹[1].1874年,美国"防止虐待动物学会"报告了第一例儿童虐待案例--玛丽.艾伦案,其中首次涉及到咬痕证据[2].咬痕多见于暴力案件和性犯罪案件,在受害人和加害人身上均可发现.许多学者认为,咬痕可以作为证据,因为咬痕特征具有明显的个体差异和相对稳定性,许多案件可以根据咬痕鉴定提供的线索和证据去破获或作正确的判决,由此可见,咬痕的法医学鉴定具有重要的实用价值.     

咬痕及其法医学鉴定

咬痕(ｂｉｔｅｍａｒｋ)是指某一个体的牙齿或牙齿与口腔其它部分一起作用于物体(人体、食物和其它物体),造成该物体在形态学上发生改变而留下的痕迹[1]。1874年,美国“防止虐待动物学会”报告了第一例儿童虐待案例———玛丽·艾伦案,其中首次涉及到咬痕证据[2]。咬痕多见于暴力案件和性犯罪案件,在受害人和加害人身上均可发现。许多学者认为,咬痕可以作为证据,因为咬痕特征具有明显的个体差异和相对稳定性,许多案件可以根据咬痕鉴定提供的线索和证据去破获或作正确的判决,由此可见,咬痕的法医学鉴定具有重要的实用价值。一、咬痕的发生情…     

Digital bite mark overlays--an analysis of effectiveness.

U.S. courts have stated that witnesses must be able to identify published works that define operational parameters of any tests or procedures that form the basis of scientific conclusions. Such works do not exist within the field of bite mark analysis. As the most commonly employed analytical technique in bite injury assessment. this study defines quantifiable variables for transparent digital overlays. A series of ten simulated, postmortem bites were created on pigskin and, with accompanying overlays, assembled into cases. Using two separate studies with four examiner groups, the study defined values of intra- and inter-examiner reliability, accuracy. sensitivity, specificity, and error rates for transparent overlays. Methods and statistical treatments from medical decision-making and diagnostic test evaluation were employed. Forced decision models and receiver operating characteristic analyses were utilized. Sensitivity and specificity values are described. and the results are consistent with other dental diagnostic systems. It was concluded that the weak inter-examiner reliability values explain the divergence of odontologists' opinions regarding bite mark identifications often stated in court. The effect of training and experience of the examiners was found to have little effect on the effective use of overlays within this study. The authors conclude that further research is required so that the results of the current study can be placed into context, but this represents a significant first step in establishing the scientific basis for this aspect of forensic dentistry.     

Analysis of distortion in preserved bite mark skin

In addition to other methods for conservation of bite mark evidence, preservation of actual skin from deceased victims is often suggested. This study was undertaken to analyze the dimensional stability of such specimens. Utilizing a prefabricated template, marks approximating "bites" were made in postmortem skin of Miniature Hanford pigs, producing imprints with distinct margins and indentations. Tissue samples were stored in 10% formalin after affixing an acrylic support ring with cyanoacrylate adhesive and sutures. Measurements of the six tooth mark analogues and cross-arch dimensions were taken at intervals of up to 38 days. Data from these measurements indicate a wide range of amount and type of distortion in preserved tissue. Although some samples were dimensionally stable, there was both contraction and expansion of bite mark specimens, even within individual skin samples. It appears that standard techniques for storage and preservation of bite mark samples will not produce reliable dimensional accuracy.     

A comparison between direct and indirect methods available for human bite mark analysis

Comparison techniques used in bite mark analysis are many and varied, the choice of technique depending largely on personal preference. Until recently, no one technique has been shown to be better than the others, and very little research has been carried out to compare different methods. This study evaluates and compares the accuracy of direct comparisons between suspects' models and bite marks with indirect comparisons in the form of conventional traced overlays of suspects' models or a new method using photocopier-generated overlays. Artificial bite marks in pigskin were made using standardized sets of models and recorded as photographs and fingerprint powder lifts on tape. The bite mark photographs and fingerprint lifts were coded and randomized so that a blind comparison could be made with the models, traced overlays, and photocopier-generated overlays using a modified version of the American Board of Forensic Odontology Scoring (ABFO) System for Bite Marks. It was found that the photocopier-generated overlays were significantly more accurate at matching the correct bite mark to the correct models irrespective of whether the bite mark was recorded photographically or as a fingerprint lift. The photocopier-generated overlays were also found to be more sensitive at matching the correct bite marks to the correct models than the other two methods used. The modified ABFO scoring system was able to discriminate between a correct match and several incorrect matches by awarding a high score to the correct match.     

两例皮肤上咬痕的DNA鉴定

在实际侦查中，皮肤上咬痕的鉴定比较注重咬痕的痕迹特征检验。由于人的皮肤在记录咬痕方面是一种很差的介质，有些咬痕特征不能得到明显的反映，因而在个人识别上的利用价值不大。应用PCR-STR技术对咬痕留在皮肤上的唾液斑进行多态DNA位点分型，可以达到个人认定或排除的目的。现就我室受理的两例皮肤上咬痕的DNA检验报告如下：     

A comparison of animal jaws and bite mark patterns

The purpose of this study was to compare the jaw shapes and bite mark patterns of wild and domestic animals to assist investigators in their analysis of animal bite marks. The analyses were made on 12 species in the Order Carnivora housed in the Mammalian Collection at the Field Museum of Natural History in Chicago, Illinois. In addition to metric analysis, one skull from each species was photographed as a representative sample with an ABFO No. 2 scale in place. Bite patterns of the maxillary and mandibular dentition were documented using foamed polystyrene exemplars, which were also photographed. A total of 486 specimens were examined to analyze the jaw and bite mark patterns. A modified technique for measuring intercanine distances was developed to more accurately reflect the characteristics seen in animal bite marks. In it, three separate areas were measured on the canines, rather than just the cusp tip. This was to maximize the amount of information acquired from each skull, specifically to accommodate variances in the depth of bite injuries.     

两例皮肤上咬痕的DNA鉴定

在实际侦查中 ,皮肤上咬痕的鉴定比较注重咬痕的痕迹特征检验。由于人的皮肤在记录咬痕方面是一种很差的介质 ,有些咬痕特征不能得到明显的反映 ,因而在个人识别上的利用价值不大。应用ＰＣＲ -ＳＴＲ技术对咬痕留在皮肤上的唾液斑进行多态ＤＮＡ位点分型 ,可以达到个人认定或排除的目的。现就我室受理的两例皮肤上咬痕的ＤＮＡ检验报告如下 :一、材料与方法1.我室在 1999年 6月及 8月受理的两起咬痕案例 ,检材为血液 (痕 ) ,唾液斑。2 .皮肤上咬痕唾液斑提取 :用干净消毒后的 1ｃｍ2 纱布沾取蒸馏水后 ,用镊子夹着纱布以同心圆方式由里向外…     

Lack of dental uniqueness between two bite mark suspects.

The central dogma of bite mark analysis is based upon two assumptions. The first is that human teeth are unique, and the second is that sufficient detail of the uniqueness is rendered during the biting process to enable identification. Both of these assumptions have been challenged over recent years, and a healthy scientific skepticism surrounding bite mark analysis has developed. The case presented features two suspects whose dental arrangement was similar and, when compared to the bite mark, both demonstrated consistent features. Within a closed population of possible biters, one of the two suspects was responsible for the injury. The case is illustrated with photographic and overlay detail of the suspect's teeth and demonstrates the complexity of such cases. The authors call for greater caution when drawing conclusions from such cases and highlight the need for further research into the replication of dental features on human skin.     

Adherence of forensic odontologists to the ABFO bite mark guidelines for suspect evidence collection

Boards and associations within forensic science have long been accepted as vehicles for the development and dissemination of protocols and recommendations for practice. Recent controversies surrounding bite mark analyses have brought the methods and practices of forensic dentists to the attention of both the courts and the media. In the mid-eighties the American Board of Forensic Odontology developed guidelines for bite mark analysis in response to unfavorable commentaries on the discipline by legal observers. The purpose of this study is to examine the adherence of board certified and noncertified forensic dentists to the guidelines for collection of evidence from bite mark suspects. A questionnaire was employed during an American Academy of Forensic Sciences meeting. Results showed that, in general, when the odontologists collected evidence they did adhere to the guidelines, although collection of salivary samples was not common. Of concern is the large number of odontologists who do not collect their own evidence from suspects. Police officers or other individuals often perform this task and therefore the guidelines must be disseminated to these groups to ensure that the maximum yield is obtained from bite mark evidence. A review of the materials used to collect evidence is also included with details of applications in forensic science.     

The use of human skin in the fabrication of a bite mark template: two case reports

Comparison of a suspected biter's dental arches with the patterned injury of a bite mark is especially difficult when the bite occurs in an anatomic location with a small radius of curvature or with complex or compound curves. The authors present two case reports in which human skin was used as a template for the reproduction of a bite. In one case the victim's skin was used; in the other, the skin of a anatomically similar person was used. The use of inked dental casts, photography, and transparent overlays significantly reduced the errors common to analysis of bite marks in these highly curved areas.     

A practical technique for the fabrication of transparent bite mark overlays

A quick, inexpensive, and accurate technique for generating transparent overlays, using office photocopy machines, for use in bite mark case analysis is presented. The critical step in the fabrication process involves determination of the accuracy of the product produced by the photocopy machine. A reliable method for making such a determination is discussed.     

Effectiveness of comparison overlays generated with DentalPrint software in bite mark analysis

Validation studies of the new DentalPrint software were carried out with experimental bite marks in pigskin. The bite marks were digitally photographed according to the ABFO guidelines for evidence collection. Dental casts used in the experiment were scanned in 3D and 2D, and comparison overlays were generated using DentalPrint and Adobe Photoshop software, respectively. Digitized photographs of the experimental bite marks and the biting edges obtained in the overlays were compared by two different examiners to analyze the impact of training and experience with the two methods. Receiver operating characteristic (ROC) analysis, sensitivity, specificity, and 95% confidence intervals for each cutoff point were calculated. The expert examiner using DentalPrint obtained the best results, with an area under the ROC curve of 0.76 (SE=0.057; CI at 95%=0.652-0.876). Fairly high specificity values were found for DentalPrint, and the best results were obtained for the cutoff value that discriminated between the examiner's response "biter" and the rest of the possible (specificity 97.9%, CI at 95%=93.2%-99.6%). Therefore, the results presented here indicate that DentalPrint is a useful, accurate tool for forensic purposes, although further research on the comparison process is needed to enhance the validity of bite mark analysis.     

The case of Ohio v. Robinson. An 1870 bite mark case

In 1870, Ansil L. Robinson was charged with the murder of his mistress, Mary Lunsford, in Mansfield, Ohio, U.S.A. Evidence against Robinson included an attempt to match his teeth to bite marks on the victim's arm. Robinson was acquitted after a 3-week trial despite the evidence linking his teeth to the wounds. This trial represents an early and perhaps the first attempt to admit bite-mark evidence in a court of law in the United States. The acquittal resulted in the obscurity that prevented this case from coming to the awareness of the forensic dental and legal communities sooner.     

A framework for estimating probability of a match in forensic bite mark identification

In forensic dentistry, a human expert typically does the comparison and identification based on bite marks. Unlike DNA analysis, however, there is no quantitative basis with which to assign a probability for this given match. This paper proposes a framework for empirically estimating the probability of such a bite mark match and reports on initial experimental results. The methodology involved collection of dental population data (3D dental casts and bite mark images), image analysis for quantitatively measuring the degree of match (based on chamfer distance), and performing a logistic regression analysis using the collected population data to estimate the probability of match from the calculated degree of match. The model correctly predicted 35 of the 42 matches and 585 of the 588 mismatches. The method also has potential for use in other forensic applications in which the assignment of quantitative probabilities is important.     

Computer-based production of comparison overlays from 3D-scanned dental casts for bite mark analysis

Bite mark analysis assumes the uniqueness of the dentition can be accurately recorded on skin or an object. However, biting is a dynamic procedure involving three moving systems, the maxilla, the mandible, and the victim's reaction. Moreover, bite marks can be distorted by the anatomic location of the injury or the elasticity of the skin tissue. Therefore, the same dentition can produce bite marks that exhibit variations in appearance. The complexity of this source of evidence emphasizes the need for new 3D imaging technologies in bite mark analysis. This article presents a new software package, DentalPrint (2004, University of Granada, Department of Forensic Medicine and Forensic Odontology, Granada, Spain) that generates different comparison overlays from 3D dental cast images depending on the pressure of the bite or the distortion caused by victim-biter interaction. The procedure for generating comparison overlays is entirely automatic, thus avoiding observer bias. Moreover, the software presented here makes it impossible for third parties to manipulate or alter the 3D images, making DentalPrint suitable for bite mark analyses to be used in court proceedings.