人牙咬痕法医学同一认定研究现状与展望

人牙咬痕因具有明显的个体差异性和相对稳定性,在实际案例中可为案件的调查取证提供依据,因此应用咬痕进行个体识别成为法医鉴定的重要组成部分。咬痕鉴定方法由来已久,其分析手段逐步进步,准确性不断提高,特别是3D识别技术初步应用于咬痕统一认定中,势必是分析手段的一个飞跃。本文将对咬痕同一认定的重要性,咬痕分析方法的发展及3D数字化应用于咬痕同一认定的必要性及展望进行综述。     

人牙咬痕形态学变化动态过程研究

目的　研究人牙咬痕形态学变化的动态过程 ,了解咬痕发生、发展的变化规律 ,为已发生变化的咬痕同一认定提供依据。方法　动态追踪观察活体及死亡动物咬痕的变化过程 ,并测定其相关形态参数 ,多元逐步回归分析咬痕形态、牙面积、时间、牙合力、牙宽度、牙厚度之间的关系 ,建立咬痕形态学变化回归方程。结果　咬痕的形态、牙形态、时间、牙合力有一定的数学关系 :S =-6 96-1 68× 10 2 T -0 11F +2 2 1W +3 75H (活体狗实验T <3 60min) ;S =-2 1 90 +5 3 4× 10 2 T -0 3 6F +4 5 7W +6 66H (死亡狗实验T <14 40min)。     

咬痕证据在法医牙科学中的应用现状及前景

咬痕越来越多见于虐童、性犯罪等暴力案件中,常是嫌疑人攻击或受害者自卫的结果。由于人类牙齿大小、形状、排列各不相同,在皮肤、食物等物体上形成的咬痕具有特征性。法医牙科学运用这个原理,将实际咬痕与口内牙痕进行比对,认定或排除嫌疑人。本文就咬痕证据的实际应用、咬痕分析的研究现状和面临的问题进行简要综述,并展望咬痕分析的前景。     

咬痕个体识别的比对方法

目的 建立一个牙模数据库,为通过牙齿、咬痕进行个人识别的研究及其在法医实践中的应用提供一种新方法。方法 经过对400例牙模进行分析、计算,将牙齿的形状、排列转换成数字型(X,Y)坐标,通过计算出每颗牙关键点与坐标原点的相对位置,在DOS系统下运用Borland C++5.0语言编写程序,快速地计算出牙齿和牙弓的特征。结果 能对牙模进行自动识别,达到排除与认定。其比对精度长度为1.3mm,角度3°;可取的最少牙点位数目为12～14较为合理,大致需要5～7个完整的牙痕。结论 该方法是研究咬痕与牙模比对的基础。     

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…     

犬咬痕法医学鉴定的研究进展及展望

犬咬人不仅是公共健康问题，也是社会安全问题，会引发诉讼。在犬咬人事件或案件中，准确认定嫌疑犬至关重要。犬咬人必然会导致咬痕的遗留。本文通过系统查阅和总结相关文献报道，从犬齿列排布特点及用途、损伤类型及形成机理、损伤部位影响因素、犬咬痕的法医学鉴定要点等方面进行综述，展望了犬咬痕法医学鉴定的应用前景，以期为我国犬咬痕法医学鉴定的相关研究提供依据。     

皮肤咬痕检验鉴定的几点体会(附2例报告)

本文通过皮肤咬痕实际案例检验,对皮肤咬痕特征及同一认定的可靠性进行了探讨,并提出皮肤咬痕检验鉴定应具备的条件和注意事项。     

人体咬痕的汉医学鉴定3例

咬痕是上下颌牙齿相对咬合作用于人体或某种物体上并进行切磨、撕扯而留下的痕迹。在法医检验，特别是性犯罪检案中，人体咬痕常掺杂于人体其他损伤之中。人体各种类型损伤中是否有咬痕、有何特异性及咬痕的同一认定，对犯罪嫌疑人的排查、甄别及认定，特别是在某些只有犯罪嫌疑人的口供的案件中，就显得尤其重要和必要。     

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：     

人体咬痕的法医学鉴定 3例

咬痕是上下颌牙齿相对咬合作用于人体或某种物体上并进行切磨、撕扯而留下的痕迹。在法医检验，特别是性犯罪检案中，人体咬痕常掺杂于人体其他损伤之中。人体各种类型损伤中是否有咬痕、有何特异性及咬痕的同一认定，对犯罪嫌疑人的排查、甄别及认定，特别是在某些只有犯罪嫌疑人的口供的案件中，就显得尤其重要和必要。     

A study of multiple bitemarks inflicted in human skin by a single dentition using geometric morphometric analysis

Criticisms of the forensic discipline of bitemark analysis state that the range of distortion in the shape of bitemark impressions in skin has not been scientifically established. No systematic statistical studies exist that explore this problem. As a preliminary investigation of this issue, a single dentition was mounted in a mechanical apparatus and used to create 89 bitemarks in human cadaver skin, both parallel and perpendicular to tension lines. Impressions of the same dentition were also created in wax. 2D scanned images of the biting dentition were obtained. Locations of incisal edges of all 6 anterior teeth as well as the midpoint of the canine were captured as landmarks in all specimens. This set of landmark data was then studied using established geometric morphometric methods. All specimen shapes were compared using Procrustes superimposition methods, and by a variation of Procrustes superimposition which preserves scale information. Match criteria were established by examining the range of variation produced by repeated measurements of the dentition for each class of specimen. The bitemarks were also compared to a population of 411 digitally scanned dentitions, again using the match criteria. Results showed that bitemarks in wax had lower measurement error than scanned images of the dentition, and both were substantially lower than measurement error as recorded in skin. None of the 89 bitemarks matched the measured shape of the biting dentition or bitemarks in wax, within the repeated measurements error level, despite the fact that all bitemarks were produced by this dentition. Comparison of the bitemarks to the collection of 411 dentitions showed that the closest match to the bitemarks was not always the same dentition that produced the bitemarks. Examination of Procrustes plots of matched shapes showed non-overlapping distributions of measurements of bitemarks in skin, wax, and the dentition. All had statistically significant differences in mean shape. Principal component analysis (PCA) and canonical variates analysis (CVA) both showed clear segregation of the three types of data. The patterns of variance revealed by PCA showed several distinct patterns produced by skin distortion; alteration of relative arch width, and varying displacement of non-aligned teeth in the dentition. These initial results indicate that when multiple suspects possess similar dentitions, bitemark analysis should be approached with caution.     

Digital analysis of experimental human bitemarks: application of two new methods

Bitemark determination in forensic odontology is commonly performed by comparing the morphology of the dentition of the suspect with life-sized photographs of injury on the victim's skin using transparent overlays or computers. The purpose of this study is to investigate the suitability of two new different methods for identification of bitemarks by digital analysis. A sample of 50 volunteers was asked to make experimental bitemarks on the arms of each other. Stone study casts were prepared from upper and lower dental arches of each volunteer. The bitemarks and the study casts were photographed; the photos were entered into the computer and Adobe Photoshop software program was applied to analyze the results. Two methods (2D polyline and Painting) of identification were used. In the 2D polyline method, fixed points were chosen on the tips of the canines and a straight line was drawn between the two fixed points in the arch (intercanine line). Straight lines passing between the incisal edges of the incisors were drawn vertically on the intercanine line; the lines and angles created were calculated. In the painting method, identification was based on canine-to-canine distance, tooth width and the thickness, and rotational value of each tooth. The results showed that both methods were applicable. However, the 2D polyline method was more convenient to use and gave prompt computer-read results, whereas the painting method depended on the visual reading of the operator.     

Anatomical location of bitemarks and associated findings in 101 cases from the United States

The purpose of this paper is to update and confirm previous studies that examined the anatomical location of human bitemarks. This information is useful to forensic odontologists and pathologists, physicians, and coroners who must be familiar with the most likely locations of bitemarks. The data are also useful for those involved in bitemark research. Using the legal database "Lexis," 101 bitemark cases were identified from the United States Courts of Appeal. Cases were included in the study if they provided details concerning the bitemark, such as anatomical location, number of injuries, and information concerning the victim. Information on 148 bites was collated. These data are presented in tabular and graphical form to allow comparisons between males and females, victims and perpetrators, adults and children, and the crime types associated with human bites.     

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.     

Inquiry into the Scientific Basis for Bitemark Profiling and Arbitrary Distortion Compensation

Abstract: Prediction of dental characteristics from a bitemark (bitemark profiling) and arbitrary photographic distortion compensation are two practices proposed in bitemark analysis. Recent research on the effect of inherent skin tension properties in bitemark analysis suggests that these practices are subject to review. A biting apparatus was used to create 66 bitemarks in human cadaver skin. The bitemarks were photographed, sized 1:1, and evaluated with Adobe Photoshop^®. Metric/angular measurements and hollow volume dental overlays were employed. Distortion produced was calculated and assessed. Results showed distortional ranges were nonuniform both between bites, as well as within each bite. Thus, enlarging/decreasing the photograph uniformly would not correct the distortion that resulted. With regard to bitemark profiling, 38% of the bites created patterns that could be misleading if profiled. Features were present/absent that were inconsistent with the biter’s dentition. Conclusions indicate bitemark profiling and arbitrary distortion compensation may be inadvisable.     

单核苷酸多态性与外在可见特征的关联及法医学意义

人群中有很多由基因导致的生理变异,可用于个人识别标志及身份证明。作为第三代遗传标记,单核苷酸多态性（SNP）已被证明与人体的许多表型差异有关。法医学可以利用SNP这个特性,通过检验SNP位点,预测犯罪者的外在可见特征（EVCs）,缩小犯罪嫌疑人范围。     

Does contextual information bias bitemark comparisons?

A growing body of research suggests that the interpretation of fingerprint evidence is open to contextual bias. While there has been suggestion in the literature that the same might apply to bitemarks – a form of identification evidence in which a degree of contextual information during the comparison phase is generally unavoidable – there have so far been no empirical studies to test this assertion. We explored dental and non-dental students' ability to state whether two bitemarks matched, while manipulating task ambiguity and the presence and emotional intensity of additional contextual information. Provision of the contextual information influenced participants' decisions on the ambiguous bitemarks. Interestingly, when participants were presented with highly emotional images and subliminally primed with the words ‘same’ and ‘guilty’, they made fewer matches relative to our control condition. Dental experience also played a role in decision-making, with dental students making more matches as the experiment progressed, regardless of context or task ambiguity. We discuss ways that this exploratory research can be extended in future studies.     

Extraction of human DNA for PCR from chewed residues of betel quid using a novel "PVP/CTAB" method

Residues of chewed betel quid (BQ) are often found on crime scenes in Taiwan and possibly some of the Southeast Asian countries. Although these residues are important biological evidences relating to the suspects, the forensic analysis of BQ evidence has been hindered by failures in extraction of human DNA for PCR analysis. Therefore, it is a prerequisite for relevant forensic casework to establish a reliable method for extracting DNA from chewed BQ residues. Three conventional methods (salt/chloroform, 5% Chelex-100 resin, and QIAamp) were first tested for extraction of human DNA from 33 mock BQ samples, which had been stored for less than two months, and 50 four-year-old forensic BQ samples. PCR amplifications from the HLA-DQA1&PM and the STR loci were then used to test the quality of the extracted DNA. For the mock samples, three observations were made. First, PCR amplification of DNA extracted by using these conventional methods had low success rate. Second, the addition of extra Taq DNA polymerase could compensate the lost enzyme activities due to putative inhibitors and, thus, increase the yield. Third, using the Centricon-100 column to remove putative inhibitors substantially improved the efficiency of PCR. However, for the four-year-old forensic BQ samples, none of the attempts for PCR were successful. In order to solve the problem in PCR analysis of DNA from old BQ samples, we developed a DNA extraction method based on the use of polyvinyl pyrrolidone (PVP) and cetyltrimethylammonium bromide (CTAB), which bind to two common classes of PCR inhibitors in plants, polyphenols, and polysaccharides, respectively. The result showed that this "PVP/CTAB" method is completely successful for the mock BQ samples, and 92% (46 out of 50) successful for the four-year-old forensic BQ samples. To our best knowledge, this is the first report of a reliable method for the extraction of human DNA for PCR from chewed BQ residues. This method should provide a useful means for forensic identification in countries where betel chewing is common.     

Three‐Dimensional Comparative Analysis of Bitemarks*

Abstract: Historically, the inability to accurately represent bitemarks and other wound patterns has limited their evidentiary value. The development of the ABFO #2 scale by Krauss and Hyzer enabled forensic odontologists to correct for most photographic plane distortions. The technique presented here uses the ABFO #2 scale in conjunction with the evolving technologies of laser scanners and comparative software commonly used by the automobile industry for three‐dimensional (3D) analysis. The 3D software comparison was performed in which measurements were analyzed of the normal distance for each point on the teeth relative to the bitemarks. It created a color‐mapped display of the bitemark model, with the color indicating the deviation at each point. There was a correlation between the bitemark and the original teeth.