Forensic odontology lessons: multishooting incident at Port Arthur, Tasmania

On Sunday 28 April 1996 a lone gunman killed and injured many people at the historic penal settlement ruins at Port Arthur in South Eastern Tasmania, Australia. Thirty-two victims were shot dead and 19 were injured in a short time inside a cafe and along the roadway leading to the site entrance. The gunman then took one hostage to a nearby guest house which was occupied by a married couple. Police stood siege during the night. Early the next day the cottage began to burn and a man suspected to be the gunman eventually ran unarmed from the building with his clothes alight and was arrested. The house burned to the ground. Three bodies were later located in the burnt ruins.Forensic odontology played a role in the retrieval of evidence and identification of the incinerated victims. Lack of antemortem dental records for one victim necessitated the reliance on a single CT scan radiograph for matching with the remains. Fire scene procedures, evidence collection and other issues were reviewed.The overwhelming scale of this tragedy and its adverse effects on the Tasmanian community, especially the victims’ families and survivors, cannot be overestimated. While acknowledging this, it is important that lessons are learnt from tragedies such as these. This paper is presented with a view to assisting forensic odontologists in the investigation of complex incidents.     

“Identified”, “probable”, “possible” or “exclude”: The influence of task-irrelevant information on forensic odontology identification opinion

In a mass disaster situation, identification of the deceased utilising comparison of dental features is frequently heavily relied upon to facilitate rapid and accurate outcomes. The method consists of the comparison of clinical and radiographic records depicting oral structures and dentition to allow an opinion to be produced on a presumed identity. Current forensic odontology identification opinions are expressed as categories of levels of identification. Categories such as “Identified”, “Probable”, “Possible” and “Exclude” are used in various forensic odontology identification scales. The boundaries between the levels of the scales are not fixed; hence, category selection is highly subjective. It is uncertain how extrinsic factors such as exposure to contextual task-irrelevant information or operator experience influence category selection. In this study, forensic odontologist and dentist participants read task-irrelevant context case information containing either strong or weak identification or non-identification suggestions before evaluating and comparing pairs of true matching and non-matching dental radiographs. They were then asked to form an opinion regarding identification using one of four categories from the INTERPOL scale. Context information was found to influence categorical decisions. The magnitude and direction of influence depended on the type of participant, the true match status of the radiographs, and the strength and direction of bias of the context. The results of this study demonstrate the contextual effect and fluidity of the boundaries between the categories on the identification scale and highlight the need for stringent protocols to be developed regarding the use of these categorical scales to enable decision making to be more objective.     

Validation studies in forensic odontology – Part 1: Accuracy of radiographic matching

As part of a series of studies aimed at validating techniques in forensic odontology, this study aimed to validate the accuracy of ante-mortem (AM)/postmortem (PM) radiographic matching by dentists and forensic odontologists. This study used a web-based interface with 50 pairs of AM and PM radiographs from real casework, at varying degrees of difficulty. Participants were shown both radiographs as a pair and initially asked to decide if they represented the same individual using a yes/no binary choice forced-decision. Participants were asked to assess their level of confidence in their decision, and to make a conclusion using one of the ABFO (American Board of Forensic Odontology), INTERPOL (International Criminal Police Organisation) and DVISys? (DVI System International, Plass Data Software) identification scale degrees. The mean false-positive rate using the binary choice scale was 12%. Overall accuracy was 89% using this model, however, 13% of participants scored below 80%. Only 25% of participants accurately answered yes or no > 90% of the time, with no individual making the correct yes/no decision for all 50 pairs of radiographs. Non-odontologists (lay participants) scored poorly, with a mean accuracy of only 60%. Use of the graded ABFO, DVISYS and INTERPOL scales resulted in general improvements in performance, with the false-positive and false-negative rates falling to approximately 2% overall. Inter-examiner agreement in assigning scale degrees was good (ICC = 0.64), however there was little correlation between confidence and both accuracy or agreement among practitioners. These results suggest that use of a non-binary scale is supported over a match/non-match call as it reduces the frequency of false positives and negatives. The use of the terms “possible” and “insufficient information” in the same scale appears to create confusion, reducing inter-examiner agreement. The lack of agreement between higher-performing and lower-performing groups suggests that there is an inconsistency in the cognitive processes used to determine similarity between radiographs.     

The role of alternative hypotheses in reducing bias in forensic medical experts’ decision making

Medical opinions are often essential evidence in criminal cases but relatively little is known about the factors that impact forensic doctors’ decision making. This research examines the role and impact of having an alternative hypothesis while forming a medical opinion. A scenario-based experiment with forensic doctors (n = 20) was conducted. In two out of three scenarios, the existence of alternative hypotheses impacted the actual opinions reached, the confidence in the judgments and the perceived consistency with the plaintiff hypothesis. Investigative and legal actors should be aware of the possibility of biases and importance of having alternative hypotheses when requesting and evaluating medical opinions.     

Proposal for internet-based Digital Dental Chart for personal dental identification in forensics

A dental chart is very useful as a standard source of evidence in the personal identification of bodies. However, the kind of dental chart available will often vary as a number of types of odontogram have been developed where the visual representation of dental conditions has relied on hand-drawn representation. We propose the Digital Dental Chart (DDC) as a new style of dental chart, especially for open investigations aimed at establishing the identity of unknown bodies. Each DDC is constructed using actual oral digital images and dental data, and is easy to upload onto an Internet website. The DDC is a more useful forensic resource than the standard types of dental chart in current use as it has several advantages, among which are its ability to carry a large volume of information and reproduce dental conditions clearly and in detail on a cost-effective basis.     

中国汉族成人颅骨CT片同一认定方法的研究

目的建立对中国汉族成人颅骨CT片进行同一认定的方法。方法按照纳入标准收集100例中国汉族成人颅骨CT片，对确定的识别指标进行观察和测量，对各指标的观测结果进行分类编码，然后按观测顺序编制特异的12位颅骨CT片识别编码。运用SPSS13．0统计学软件对所得数据进行各指标年龄和性别差异的统计学分析，利用个人识别能力公式计算单个指标和总体指标的个人识别能力。结果12项识别指标中有6个指标存在男女性别差异；12项指标累计个人识别能力可达到99．9997997％。结论本文确定中国汉族成人颅骨CT片12项观测指标，利用指标分类编码法可进行中国汉族成人颅骨CT片的同一认定。     

Third molar development according to chronological age in populations from Spanish and Magrebian origin

Spain is frequently the entrance country into the European Union for undocumented immigrants, especially those from the Magreb (Northern Africa). Forensic age estimates for these persons are difficult because systematic studies of dental maturity are lacking. Three different populations were analyzed to determine the pattern of development of third molars as a tool for age estimation in people of different ethnic and geographic origin. Orthopantomograms from two different populations of Spanish origin (Galicia in northwestern continental Spain, and Ceuta, a Spanish province in Northern Africa) were compared to radiographs of molars from a Magrebian population (Northern Africa) resident in Ceuta. Orthopantomograms were obtained from a private dental clinic (n=344) in Galicia and from the Public Oral Health Services (n=228) in Ceuta. We looked for differences in third molar mineralization (determined with the Demirjian scale) that might serve as age indicators (older versus younger than 18 years). Differences in maturation patterns were found between sexes and populations of origin. Mineralization of tooth 38 was more advanced in males than females among subjects 18 years of age and older in all three populations. Moreover, mineralization of tooth 38 in subjects aged 18 years and older was significantly slower in the Spanish-Galicia population than in the Magrebian-Ceuta population. We found no significant differences between Magrebian and Spanish individuals from Ceuta. We conclude that differences in tooth 38 mineralization may be related more with socio-geographical than ethnic origin (ancestry), and thus constitute evidence of the relevance of socio-geographic rather than genetic factors in third molar development. We used ROC analysis to determine the accuracy of the examiner's ability to correctly estimate age as younger or older than 18 years. The results suggest that Demirjian stage for tooth 38 can be considered a good indicator of age in all three populations.     

Comparison of simulated human dermal bitemarks possessing three-dimensional attributes to suspected biters using a proprietary three-dimensional comparison

The infliction of a bite is a four-dimensional space–time event that is ideally analyzed with three-dimensional (3-D) technology. Comparison of 2-D images (photographs) of a bitemark with a 3-D replica of a suspect's dentition is challenging. The authors present a technique that produces 3-D images of indented marks and dentitions for comparisons. Study models and corresponding dental-wax bites were digitized by 3-D scanning, and comparison overlays were generated using DentalPrint^© software. The effectiveness of the method was analyzed by determining the area under receiver operating characteristic (ROC) curve and the sensitivity, specificity and 95% confidence interval (CI) for each cut-off point. An area under the ROC curve of 0.953 (SE = 0.029; 95% CI = 0.893–0.985) and high sensitivity and specificity values were obtained for 104 comparisons made by an expert examiner, who correctly identified 92.3% of matching dentitions and 98.7% of non-matching dentitions. This technique can be considered a highly accurate method of bitemark analysis, although indentations must be present in the injury, limiting the cases that can be resolved. A comparative study of the same dentitions using 2-D bitemark photography confirmed the superiority of the new approach.     

二元制抑或一元制：医疗纠纷鉴定模式的选择

医疗（事故）纠纷因专门性问题源于医疗事故技术鉴定和司法鉴定的＂二元制＂鉴定模式,致使纠纷解决的法律在选择适用上出现不同的结果,并造成了同一事实的处理结果尤其是赔偿的数额差异甚巨。《侵权责任法》的实施能否终结＂二元制＂鉴定模式,使冲突的相关规定、解释、解答等相关文本在法律适用上归于统一再次成为颇具争论的问题。基于医疗事故技术鉴定与司法鉴定结果在证据性质上的同一,有必要将医疗事故技术＂鉴定＂仅作为行政程序的内容,并进一步建立解决医疗纠纷的鉴定机制,体现鉴定作为证据的＂认定＂功能,以便实现医疗行为共担风险以及利益平衡的基本目标。     

眼损伤法医学错误鉴定分析（附2例分析）

眼损伤法医学鉴定是法医临床学鉴定中的难点和研究热点,也是最容易出现错误鉴定的地方。本文针从两例错误鉴定入手,分析错误鉴定主要原因,一是鉴定人未关注病历材料中显示的重要信息,对病历材料中反映的既往病史、损伤动态发展及检查结果未予重视：二是鉴定人不具备眼损伤检查的基本技能,过度依赖外部信息。三是鉴定人不具备眼损伤的基础专业知识．对各类信息缺乏准确认识．对常见的眼损伤转归及预后不掌握。因此,结合上述问题,笔者建议鉴定人应当采取以下对策阻止或减少错误鉴定的发生,（1）完整审阅病历资料、影像学资料是基础;（4）实施细致、完善检查是关键;（3）准确把握鉴定标准是核心;（4）加强鉴定人专业技能和法律意识的提高是根本。     

The survival of oral streptococci on human skin and its implication in bite-mark investigation

Ten-microlitre aliquots of whole saliva applied to human skin were sampled for periods up to 6.25 h. The rate of loss of recoverable bacteria was 45–50% per hour. After 6.25 h, viable oral streptococci could be recovered. The implications for using a “fingerprint” typing method for these bacteria with regard to the identification of bite-marks are discussed.     

头颅放射影像资料的同一认定

利用放射影像资料进行法医临床学鉴定案例越来越多。同一认定常使用的标志包括牙齿、头颅、脊柱等相关特征结构。头颅放射影像资料,包括X片及CT片中的额窦、乳突、蝶鞍、颅缝及其他结构均可作为同一认定的标志。目前,我国法医放射学尚属起步阶段,应加强此方面的研究。     

Radiographic evaluation of third molar development in relation to chronological age among Turkish children and youth

A sharp increase in forensic age estimation of living persons has been observed in recent years. However, ethnic populations residing in different countries have been insufficiently analyzed. According to 2004 data compiled by the Essen-based Turkey Research Center, there are 3.8 million Turkish people living abroad, and 3.2 million of them reside in European Union countries. Despite the high number of Turks living abroad, little is known about third-molar development for forensic application in this population. Hence, it was considered worthwhile to determine the developmental stages of the third molar in a group of Turkish population, to assess chronological age estimation based on the developmental stages, and to compare third molar development according to sex, age and location. Orthopantomograms of 1134 Turkish patients, ages 4-20 years were examined and third-molar developmental stages were evaluated based on Demirjian's classifications. Orthopantomograms were scored by two different observers, and Wilcoxon matched-pairs signed-ranks test used to test intra- and inter-observer reliability revealed a strong agreement between both intra- and inter-observer measurements. Linear regression analysis was performed to correlate third-molar development and chronological age, and further statistical analysis was performed to determine the relation between sex, age and location. Results showed a strong linear correlation between age and molar development (males: r(2)=0.57; females: r(2)=0.56). Mineralizations of left and right third molars were compared using Wilcoxon tests, and no statistical differences were found. No significant differences were found in third-molar development between males and females. Mandibular third molar crypt formation was observed in 2.4% of patients at age seven and maxillary third molar crypt formation was observed in 1.3% of patients at age seven. A strong correlation was found between third-molar development and chronological age. Among the Turkish population, third molar crypt formation is observable at as early as 7 years in both the mandible and maxilla. Agenesis can be determined conclusively if no radiolucent bud is present by age 14.     

Univariate sex dimorphism in the Nepalese dentition and the use of discriminant functions in gender assessment

Sex dimorphism in the Nepalese dentition is described using univariate and discriminant analyses. Canines showed the greatest univariate sex dimorphism, followed by the buccolingual (BL) dimension of maxillary first and second molars. Overall, the maxillary teeth and BL dimensions showed greater univariate sex differences. However, less than half of the measured variables (46.4%) showed statistically significant differences between the sexes and the magnitude of sex dimorphism was reduced when compared to other populations. Moreover, reverse dimorphism--where females showed larger teeth than males--was observed in the mesiodistal dimension of mandibular second premolars. This reflects reduction in sexual dimorphism observed through human evolution and the consequent overlap of tooth dimensions in modern males and females. A specific purpose of the study was to develop discriminant functions to facilitate sex classification. A group of functions were developed considering the possibility of missing teeth and/or jaws in forensic scenarios. The functions permitted moderate to high classification accuracy in sexing (67.9% using maxillary posterior teeth; 92.5% using teeth from both jaws). The superior expression of sex dimorphism by means of discriminant functions is in contrast to the univariate results. This is due to discriminant analysis utilising the inter-relationship between all teeth within a dentition--these tooth correlations are not utilised in univariate analysis which results in a loss of information. It is inferred that large-scale statistically significant univariate differences are not a prerequisite for sex assessment.     

Accuracy of developing tooth length as an estimate of age in human skeletal remains: the deciduous dentition

Dental age assessments are widely used to estimate age of immature skeletal remains. Most methods have relied on fractional stages of tooth emergence and formation, particularly of the permanent dentition, for predicting the age of infants and very young children. In this study, the accuracy of regression equations of developing deciduous tooth length for age estimation (Liversidge et al.) is tested on a sample of 30 Portuguese subadult skeletons of known age at death. Overall the method shows high accuracy and the average difference between estimated and chronological age is between 0.20 and -0.14 years when using single teeth, and 0.06 years, when using all available teeth. However, there is a tendency for the deciduous molars to provide overestimates of chronological age. Results show that age estimates can be obtained within +/-0.10 years with a 95% confidence interval when several teeth are used. Overall between-tooth agreement in age estimates decreases with increasing age but there is less variability of estimates with more teeth contributing to overall mean age. One seemingly limitation of this method may be the fact that it was developed by combining the maxillary and mandibular teeth. The other is related to the accuracy with which radiographic tooth length can be used as a valid surrogate for actual tooth length. Nevertheless, the advantages of this metric method surpass the limitations of chronologies based on stages of dental development.     

DNA条形码技术在法庭科学种属鉴定中的应用

DNA条形码(DNA Barcoding)技术提出10余年,目前已成为国内外食品安全和动物保护等相关领域种属鉴定的新热点,该技术可实现生物样本的快速、准确识别和种属鉴定,为司法实践提供所需的科学证据。本文综述了DNA条形码技术的原理、发展及应用前景。