Radiographic human identification using bones of the hand: a validation study

The 1993 Supreme Court case Daubert v. Merrell-Dow Pharmaceuticals, Inc. underscores the importance of validating forensic science techniques. This research examines the validity of using posterior-anterior radiographs of the hand to make positive identifications of unknown human remains. Furthermore, this study was constructed to satisfy the requirements of Daubert's guidelines of scientific validity by establishing a standard methodology for hand radiograph analysis, testing the technique, and noting rates of error. This validation study required twelve participant examiners from the forensic science community, working independently, to attempt to match 10 simulated postmortem radiographs of skeletonized hands to 40 simulated antemortem radiographs of fleshed cadaver hands. The overall accuracy rate of the twelve examiners was 95%, while their collective sensitivity and specificity were 95% and 92%, respectively. However, the accuracy of each examiner was related to the amount of radiological training and experience of the observer. Six Ph.D. forensic anthropologists and four experienced forensic anthropology graduate students correctly identified all the matches. Participant examiners noted bone morphology, trabecular patterns of the proximal and middle phalanges, and distinctive radiopaque and radiolucent features as the anatomical features that aided the identification process. The hand can be an important skeletal element for radiographic positive identification because it contains 27 individual bones for comparative analysis.     

Error and its Meaning in Forensic Science

The discussion of “error” has gained momentum in forensic science in the wake of the Daubert guidelines and has intensified with the National Academy of Sciences' Report. Error has many different meanings, and too often, forensic practitioners themselves as well as the courts misunderstand scientific error and statistical error rates, often confusing them with practitioner error (or mistakes). Here, we present an overview of these concepts as they pertain to forensic science applications, discussing the difference between practitioner error (including mistakes), instrument error, statistical error, and method error. We urge forensic practitioners to ensure that potential sources of error and method limitations are understood and clearly communicated and advocate that the legal community be informed regarding the differences between interobserver errors, uncertainty, variation, and mistakes.     

Wrongful convictions and claims of false or misleading forensic evidence

The results are reported of a study to examine case factors associated with 732 wrongful convictions classified by the National Registry of Exonerations as being associated with “False or Misleading Forensic Evidence.” A forensic error typology has been developed to provide a structure for the categorization and coding of factors relating to misstatements in forensic science reports; errors of individualization or classification; testimony errors; issues relating to trials and officers of the court; and evidence handling and reporting issues. This study, which included the analysis of 1391 forensic examinations, demonstrates that most errors related to forensic evidence are not identification or classification errors by forensic scientists. When such errors are made, they are frequently associated with incompetent or fraudulent examiners, disciplines with an inadequate scientific foundation, or organizational deficiencies in training, management, governance, or resources. More often, forensic reports or testimony miscommunicate results, do not conform to established standards, or fail to provide appropriate limiting information. Just as importantly, actors within the broader criminal justice system—but not under the purview of any forensic science organization—may contribute to errors that may be related to the forensic evidence. System issues include reliance on presumptive tests without confirmation by a forensic laboratory, use of independent experts outside the administrative control of public laboratories, inadequate defense, and suppression or misrepresentation of forensic evidence by investigators or prosecutors. In approximately half of wrongful convictions analyzed, improved technology, testimony standards, or practice standards may have prevented a wrongful conviction at the time of trial.     

Validation of powder X-ray diffraction following EN ISO/IEC 17025

Powder X-ray diffraction (PXRD) is used widely in forensic science laboratories with the main focus of qualitative phase identification. Little is found in literature referring to the topic of validation of PXRD in the field of forensic sciences. According to EN ISO/IEC 17025, the method has to be tested for several parameters. Trueness, specificity, and selectivity of PXRD were tested using certified reference materials or a combination thereof. All three tested parameters showed the secure performance of the method. Sample preparation errors were simulated to evaluate the robustness of the method. These errors were either easily detected by the operator or nonsignificant for phase identification. In case of the detection limit, a statistical evaluation of the signal-to-noise ratio showed that a peak criterion of three sigma is inadequate and recommendations for a more realistic peak criterion are given. Finally, the results of an international proficiency test showed the secure performance of PXRD.     

中外法庭科学标准化研究现状比较与发展趋势

近年来,我国法庭科学发展迅猛,开始受到广泛关注和重视。经过多年的研究和推动,标准化正逐步深入到法庭科学的日常实践中,通过制定和实施标准规范,确保法庭科学结果质量,更好发挥科学技术在执法司法中的重要作用。标准化研究是法庭科学标准化工作的重要环节,也是推动法庭科学标准化发展的基础和动力。国内外法庭科学研究者都高度重视法庭科学标准化研究,许多新理念、新思想、新方法不断涌现。本文从标准定位、标准化对象、标准颗粒度、标准体系、质量控制、国际标准化六个方面对当前中外法庭科学标准化研究的现状进行了深入全面的归纳和比较,指出了国内外在法庭科学标准化研究方面的相似和差异,并对法庭科学标准化研究的未来发展趋势进行了分析,以求为推动我国法庭科学领域标准化工作高质量发展提供借鉴和参考。     

Forensic Confirmation Bias: Do Jurors Discount Examiners Who Were Exposed to Task-Irrelevant Information?*†

Knowledge of task-irrelevant information influences judgments of forensic science evidence and thereby undermines their probative value (i.e., forensic confirmation bias). The current studies tested whether laypeople discount the opinion of a forensic examiner who had a priori knowledge of biasing information (i.e., a defendant's confession) that could have influenced his opinion. In three experiments, laypeople (N = 765) read and evaluated a trial summary which, for some, included testimony from a forensic examiner who was either unaware or aware of the defendant's confession, and either denied or admitted that it could have impacted his opinion. When the examiner admitted that the confession could have influenced his opinion, laypeople generally discounted his testimony, as evidenced by their verdicts and other ratings. However, when the examiner denied being vulnerable to bias, laypeople tended to believe him—and they weighted his testimony as strongly as that of the confession-unaware examiner. In short, laypeople generally failed to recognize the superiority of forensic science judgments made by context-blind examiners, and they instead trusted examiners who claimed to be impervious to bias. As such, our findings highlight the value of implementing context management procedures in forensic laboratories so as not to mislead fact-finders.     

物证鉴定的技术方法确认和标准操作规程

物证鉴定中使用的技术方法直接影响和决定了物证检验结果的质量,因此对技术方法的管理是物证鉴定实验室质量保证体系的核心因素之一。开展技术方法的开发确认和内部确认并建立方法的标准操作规程,是保证实验室能够正确选择和使用科学可靠的技术方法,并获得一致结果的主要手段。运行高水平质量保证体系的物证鉴定实验室,应该在案件物证检验工作中使用经过实验室内部确认的技术方法,而且重要新技术方法还应在开发确认基础上进行内部确认,根据方法确认结果建立该方法的标准操作规程。     

Observer determination of the make,model, and year of questioned vehicles

Often, criminal acts involving a vehicle are caught on digital video surveillance systems. While potentially useful for an investigation, the recording conditions are typically less than optimal for the extraction of key information for the identification of the perpetrator, such as a license plate. Providing the make, model and year of a questioned vehicle is a common request for examiners, to narrow the field of potential suspect vehicles. This study seeks to compare the performance of a nonpeer-reviewed make, model, and year determination between two separate groups, specifically, trained forensic image examiners and nontrained individuals. Results show that even with varied image capture conditions and quality, the trained forensic image examiners more correctly and completely identified the test group of questioned vehicles make, model, and year.     

Pistol image retrieval by shape representation

Databases have been used to record data in forensic science, such as fingerprints, shoeprints, and photos. In traditional databases, we use “text” as the “keyword” for retrieving data (text-keyword retrieval); however, in some applications, “text” is not proper to describe the searching target, and in this case, “image” plays an important role. In this paper, we use “image features” as the “keywords”, and show its potential for building up a prototype of pistol image databases.In current firearm databases of forensic science, the retrieval method is still by text-keyword retrieval. For experienced forensic examiners, this kind of databases may satisfy their requirement. However, for people who have little gun knowledge, how can they find the possible gun candidates or similar guns in the databases, if there are not any available words or marks on the gun? In this paper, we try to retrieve similar pistol images by the pistol shape instead of “text-keyword”. This method can narrow down the searching range while identifying pistols by firearm databases.There are more than 300 pistol images in our pistol image database. From the experimental results, we can retrieve the similar pistol images in top five candidates for each pistol image.     

Non-destructive dental-age calculation methods in adults: intra- and inter-observer effects

The aim of the present study was to obtain data on the reliability and reproducibility of two non-destructive dental-age estimation methods in adults by calculating inter- and intra-observer effects. Both a morphological and a radiological technique available in the scientific literature were evaluated on a number of recently extracted teeth: the morphological technique was evaluated on a total of 160 teeth by two examiners, while three examiners applied the radiological technique on apical radiographs of 72 extracted teeth. Paired t-tests were used to calculate intra- and inter-observer differences. For the morphological method, both examiners were able to produce dental-age estimations that did not differ significantly from the real age of the teeth, obtaining a mean error between 0.5 and 1.8 years and a standard deviation of this error between 9.0 and 11.3 years. When using the radiological technique according to the original protocol, all three examiners produced age estimations that were statistically comparable to the real age of the teeth with a mean error of 0.5-2.5 years and a standard deviation of 4.6-9.8 years. For both techniques, intra-observer differences were observed. Based on the results of this study, it can be concluded that both non-destructive dental-age estimation techniques were able to produce reasonably accurate dental-age estimations, at least when these techniques were applied appropriately. However, the forensic odontologist is recommended to use different age estimation techniques and perform repetitive measurements in order to verify the reproducibility of the calculations performed.     

Organizational and Human Factors Affecting Forensic Decision-Making: Workplace Stress and Feedback

Although forensic examiners operate in a stressful environment, there is a lack of understanding about workplace stress and feedback. These organizational and human factors can potentially impact forensic science judgments. In this study, 150 practicing forensic examiners from one laboratory were surveyed about their experiences of workplace stress, and the explicit and implicit feedback they receive. Forensic examiners reported that their high stress levels originated more from workplace-related factors (management and/or supervision, backlogs, and the pressure to do many cases) than from personal related factors (family, medical, and/or financial). The findings showed that a few (8%) of the forensic examiners sometimes felt strong implicit feedback about what conclusions were expected from them and that some (14%) also strongly felt that they were more appreciated when they helped to solve a case (e.g., by reaching a “match” as opposed to an “inconclusive” conclusion). Differences were found when comparing workplace stress and feedback levels across three core forensic science fields (forensic biology, chemistry, and latent prints) and across career stages (early, mid, and late). Gaining insights into the stress factors within a workplace and explicit and implicit feedback has implications for developing policies to improve the well-being, motivation, and performance of forensic examiners.     

Assessing Cognitive Bias in Forensic Decisions: A Review and Outlook

In recent years, a number of studies have demonstrated that forensic examiners can be biased by task-irrelevant contextual information. However, concerns relating to methodological flaws and ecological validity attenuate how much the current body of knowledge can be applied to real-life operational settings. The current review takes a narrative approach to synthesizing the literature across forensic science. Further, the review considers three main issues: (i) primary research on contextual bias within forensic science; (ii) methodological criticisms of this research; (iii) an alternative perspective that task-irrelevant contextual information does not always lead to error. One suggestion for future research is outlined, which is that studies on contextual bias in forensic decisions should be conducted in collaboration between forensic scientists and cognitive psychologists. Only then can rigorous and ecological valid experiments be created that will be able to assess how task-irrelevant contextual information influences forensic analysis and judgments in operationally valid settings.     

Human height estimation from highly distorted surveillance image

Video surveillance camera (VSC) is an important source of information during investigations especially if used as a tool for the extraction of verified and reliable forensic measurements. In this study, some aspects of human height extraction from VSC video frames are analyzed with the aim of identifying and mitigating error sources that can strongly affect the measurement. More specifically, those introduced by lens distortion are present in wide-field-of-view lens such as VSCs. A weak model, which is not able to properly describe and correct the lens distortion, could introduce systematic errors. This study focuses on the aspect of camera calibration to verify human height extraction by Amped FIVE software, which is adopted by the Forensic science laboratories of Carabinieri Force (RaCIS), Italy. A stable and reliable approach of camera calibration is needed since investigators have to deal with different cameras while inspecting the crime scene. The performance of the software in correcting distorted images is compared with a technique of single view self-calibration. Both approaches were applied to several frames acquired by a fish-eye camera and then measuring the height of five different people. Moreover, two actual cases, both characterized by common low-resolution and distorted images, were also analyzed. The height of four known persons was measured and used as reference value for validation. Results show no significant difference between the two calibration approaches working with fish-eye camera in test field, while evidence of differences was found in the measurement on the actual cases.     

IoT forensics: Exploiting unexplored log records from the HIKVISION file system

CCTV surveillance systems are IoT products that can be found almost everywhere. Their digital forensic analysis often plays a key role in solving crimes. However, it is common for these devices to use proprietary file systems, which frequently hinders a complete examination. HIKVISION is a well-known manufacturer of such devices that typically ships its products with its proprietary file system. The HIKVISION file system has been analyzed before but that research has focused on the recovery of video footage. In this paper, the HIKVISION file system is being revisited regarding the log records it stores. More specifically, these log records are thoroughly examined to uncover both their structure and meaning. These unexplored pieces of evidence remain unexploited by major commercial forensic software, yet they can contain critical information for an investigation. To further assist digital forensic examiners with their analysis, a Python utility, namely the Hikvision Log Analyzer, was developed as part of this study that can automate part of the process.     

Explosion Scene Forensic Image Interpretation

Image interpretation is an important aspect in the field of forensic science; however, it is seldom reported how to use these techniques in explosion scene forensic investigations. On 12 August 2015, a series of explosions killed 165 people and injured hundreds more at a container storage station at the Port of Tianjin. In this study, we applied image interpretation methods to determine the seat of the explosion by analyzing low‐quality video clips of the event. The interpretation fits well with recently published standard operating procedures, including the hypothesis, evaluation, inference, and confirmation. Image processing was adopted to enhance the images while the explosion scene was reconstructed with the same images. Some important features were extracted and utilized to distinguish whether the flashes were caused by reflection or a real blast. We reveal the real explosion location, which guides the overall investigation. The results indicate that image interpretation is a powerful tool for forensic investigators to analyze low‐quality images in complicated explosions or fire accidents.     

If error rate is such a simple concept,why don’t I have one for my forensic tool yet?

The Daubert decision motivates attempts to establish error rates for digital forensic tools. Many scientific procedures have been devised that can answer simple questions. For example, does a soil sample contain component X? A procedure can be followed that gives an answer with known rates of error. Usually the error rate of a process that tries to detect something is associated with a random component of some measurement. Typically there are two types of error, type I, also called a false positive (detecting it when it is not really there), and type II, also called a false negative (missing it when it really is there). At first thought, an error rate for a forensic acquisition tool or a write blocking tool is a simple concept. An obvious possibility for the error rate of an acquisition is k/n, where n is the total number of bits acquired and k is the number of incorrectly acquired bits. However, the kinds of errors in the soil test and in digital acquisition are fundamentally different. The errors in the soil test can be modeled with a random distribution that can be treated statistically, but the errors that occur in a digital acquisition are systematic and triggered by specific conditions. The purpose of this paper is not to define any error rates for forensic tools, but identification of some of the basic issues to stimulate discussion and further work on the topic.     

What does method validation look like for forensic voice comparison by a human expert?

Method validation has gained traction within forensic speech science. The community recognises the need to demonstrate that the analysis methods used are valid, but finding a way to do so has been more straightforward for some analysis methods than for others. This article addresses the issue of method validation for the Auditory Phonetic and Acoustic (AuPhA) approach to forensic voice comparison. Although it is possible to take inspiration from general regulatory guidance on method validation, it is clear that these cannot be transposed on to all forensic analysis methods with the same degree of success. Particularly with respect to an analysis method like AuPhA, and in a field of the size and characteristics of forensic speech science, a bespoke approach to method validation is required. In this article we address the discussions that have been taking place around method validation, and illustrate one possible solution to demonstrating the validity of voice comparison by a human expert using the AuPhA method. In doing so we consider the constraints placed on sole practitioners, which generally go unacknowledged.     

Expertise in Fingerprint Identification

Although fingerprint experts have presented evidence in criminal courts for more than a century, there have been few scientific investigations of the human capacity to discriminate these patterns. A recent latent print matching experiment shows that qualified, court‐practicing fingerprint experts are exceedingly accurate (and more conservative) compared with novices, but they do make errors. Here, a rationale for the design of this experiment is provided. We argue that fidelity, generalizability, and control must be balanced to answer important research questions; that the proficiency and competence of fingerprint examiners are best determined when experiments include highly similar print pairs, in a signal detection paradigm, where the ground truth is known; and that inferring from this experiment the statement “The error rate of fingerprint identification is 0.68%” would be unjustified. In closing, the ramifications of these findings for the future psychological study of forensic expertise and the implications for expert testimony and public policy are considered.     

数码翻拍的图像质量分析及应用标准化探讨

翻拍是司去鉴定中固定平面类证据的常用方法之一。数码翻拍突破了传统翻拍的界限。提供了高效方法。但其图像质量及应用标准化研究尚未形成体系。本文以数码相机为例，深入分析影响翻拍质量的各因素，并对其在司法实践中如何保证和提高翻拍质量进行技术方法上的探讨。通过分析研究。界定了数码翻拍中器材使用标准、拍摄条件标准及操作标准。为司法鉴定中的翻拍应用标准化提供了借鉴与参考。     

An efficient method to detect series of fraudulent identity documents based on digitised forensic data

Document fraud is a transnational form of crime, and its serial character has already been highlighted. To combat this phenomenon, the Interstate Database of Fraudulent Identity Documents (BIDIF) has been created and implemented in Switzerland. It supports the comparison of documents and the detection of series, i.e., documents that share a common source. To efficiently use such a system, forensic document examiners would benefit from a harmonised and proven profiling method. Thus, the aim of this study is to develop a method for comparing documents and establishing series. The method is meant to improve the detection capabilities of forensic document examiners operating BIDIF or engaged in the profiling of fraudulent documents. First, a method based on the visual characteristics of digitised images of fraudulent identity documents has been developed. Subsequently, the method was qualitatively and quantitatively evaluated using four tests. The first test verified the ability of the method to detect pre-existing series. The second test checked the capability of the method to detect links amongst isolated documents. Finally, two further tests were carried out to compare the method impact on the successful detection of series. These tests were carried out by professional forensic document examiners and Master students in forensic science, respectively. This allowed a comparison of the method influence on series detection. The method allowed a significant increase in the number of series and links detected, while also decreasing the occurrence of false negatives and false positives. Furthermore, links were more rapidly detected.