Context effects and observer bias--implications for forensic odontology

Psychologists have long recognized the effects of contextual and extraneous information on decision making. Such information renders the subject susceptible to both motivational and cognitive bias; yet, it is difficult to assess the extent to which these influence forensic odontologists opinions as there have been no studies to date on this subject. This article explores the various types of contextual effects and biasing influences that potentially impact on the analysis of bitemarks in forensic odontology. It appears that the current practice of bitemark analysis is rich in sources of potentially biasing influences. In addition to the fundamental recognition that some form of bias is likely to exist, ways in which these should be minimized include: separation of the collection and analysis phases; limiting the amount of contextual information available to the odontologist responsible for the analysis; and ensuring that evidence that is ambiguous or of poor quality is identified as such prior to analysis.     

美国法庭科学证据的应用与发展

＂法庭科学＂萌芽于古代中国,兴盛于近现代西方国家,最终发展成为具备完整科学体系的现代意义上的法庭科学学科。法庭科学证据的应用与发展显然与法庭科学的发展与应用密切相关,它们相互制约,相互促进。美国司法制度中关于法庭科学证据的证明力、可信度、可采性的分立质疑对法庭科学本身的发展无疑起到鞭策与促进作用。美国法庭科学证据的司法制度以及常用的一些传统与高技术法庭科学证据的使用过程中存在的许多问题,理解法庭科学证据标准,对我国法庭科学及其证据的研究与应用有所启迪。     

A Perspective on Errors,Bias, and Interpretation in the Forensic Sciences and Direction for Continuing Advancement*

Abstract: The forensic sciences are under review more so than ever before. Such review is necessary and healthy and should be a continuous process. It identifies areas for improvement in quality practices and services. The issues surrounding error, i.e., measurement error, human error, contextual bias, and confirmatory bias, and interpretation are discussed. Infrastructure is already in place to support reliability. However, more definition and clarity of terms and interpretation would facilitate communication and understanding. Material improvement across the disciplines should be sought through national programs in education and training, focused on science, the scientific method, statistics, and ethics. To provide direction for advancing the forensic sciences a list of recommendations ranging from further documentation to new research and validation to education and to accreditation is provided for consideration. The list is a starting point for discussion that could foster further thought and input in developing an overarching strategic plan for enhancing the forensic sciences.     

Naturalistic decision making in forensic science: toward a better understanding of decision making by forensic team leaders

This study uses the naturalistic decision-making (NDM) perspective to examine how Dutch forensic team leaders (i.e., the officers in charge of criminal forensic research from the crime scene until the use of laboratory assistance) make decisions in real-life settings and identifies the contextual factors that might influence those decisions. First, a focus group interview was conducted to identify four NDM mechanisms in day-to-day forensic decision making. Second, a serious game was conducted to examine the influence of three of these contextual mechanisms. The results uncovered that forensic team leaders (i) were attracted to obtain further information when more information was initially made available, (ii) were likely to devote more attention to emotionally charged cases, and (iii) used not only forensic evidence in the decision making but also tactical, unverified information of the police inquiry. Interestingly, the measured contextual influences did not deviate significantly from a control group of laypeople.     

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.     

Single cells for forensic DNA analysis--from evidence material to test tube

Abstract: The purpose of this project was to develop a method that, while providing morphological quality control, allows single cells to be obtained from the surfaces of various evidence materials and be made available for DNA analysis in cases where only small amounts of cell material are present or where only mixed traces are found. With the SteREO Lumar.V12 stereomicroscope and UV unit from Zeiss, it was possible to detect and assess single epithelial cells on the surfaces of various objects (e.g., glass, plastic, metal). A digitally operated micromanipulator developed by aura optik was used to lift a single cell from the surface of evidence material and to transfer it to a conventional PCR tube or to an AmpliGrid^® from Advalytix. The actual lifting of the cells was performed with microglobes that acted as carriers. The microglobes were held with microtweezers and were transferred to the DNA analysis receptacles along with the adhering cells. In a next step, the PCR can be carried out in this receptacle without removing the microglobe. Our method allows a single cell to be isolated directly from evidence material and be made available for forensic DNA analysis.     

Child abduction murder: the impact of forensic evidence on solvability

This study examined 733 child abduction murders (CAMs) occurring from 1968 to 2002 to explore the influence of forensic evidence on case solvability in CAM investigations. It was hypothesized that the presence of forensic evidence connecting the offender to the crime would enhance case solvability in murder investigations of abducted children. This study examined the impact of CAM of different types of forensic evidence and the impact of the summed total of forensic evidence items on case solvability by controlling for victim age, victim race, victim gender, and victim-offender relationship. Time and distance theoretical predictors were also included. Binomial logistic regression models were used to determine whether forensic evidence was a critical solvability factor in murder investigations of abducted children. This research indicated that, while forensic evidence increased case solvability, the impact of forensic evidence on solvability was not as important as other solvability factors examined.     

Meta-analytically quantifying the reliability and biasability of forensic experts

Abstract:  In this paper we employ meta-analytic procedures and estimate effect sizes indexing the degree of reliability and biasability of forensic experts. The data are based on within-expert comparisons, whereby the same expert unknowingly makes judgments on the same data at different times. This allows us to take robust measurements and conduct analyses that compare variances within the same experts, and thus to carefully quantify the degree of consistency and objectivity that underlie expert performance and decision making. To achieve consistency, experts must be reliable, at least in the very basic sense that an expert makes the same decision when the same data are presented in the same circumstances, and thus be consistent with themselves. To achieve objectivity, experts must focus only on the data and ignore irrelevant information, and thus be unbiasable by extraneous context. The analyses show that experts are not totally reliable nor are they unbiasable. These findings are based on fingerprint experts decision making, but because this domain is so well established, they apply equally well (if not more) to all other less established forensic domains.     

Value of DNA tests: a decision perspective

ABSTRACT: Before a Court of Law testifying in DNA‐evidence cases, scientists are often challenged with the idea that the more markers (loci) the better, i.e., why does the scientist not use 16 or more markers? This paper introduces a new perspective, decision analysis, to deal with the problem of the number of markers to type in a criminal context. The decision‐making process, which plays a key role in the routine work of a forensic scientist, consists of the rational choice, given personal objectives, between two or more possible outcomes when the consequences of the choice are uncertain. Simulated results support the hypothesis that analytical added value does not increase with the number of markers.     

Analysis of alprazolam by DART-TOF mass spectrometry in counterfeit and routine drug identification cases

The high prevalence of alprazolam abuse translates to an increased workload for crime laboratories in characterizing seized tablets. These tablets may originate as diverted pharmaceuticals or counterfeited mimics, so efficient analytical techniques should provide confirmatory data while minimizing destruction of evidence. We offer the first report of a validated forensic method for confirming alprazolam tablets by direct analysis in real time-time of flight (DART-TOF) mass spectrometric analysis. This technique provides rapid identification of target analytes with minimal sample preparation, allowing direct analysis in the atmospheric sample gap. Selectivity is achieved through high resolution and mass accuracy, unique ion fragments, and chlorine isotopic ratios. This method utilizes fragmentation in two separate voltage functions to observe the alprazolam pseudo molecular ion at 309.09070 using 40 V and major ion fragments of 281.07197 and 205.07657 at 120 V. These parameters allow our laboratory to confirm alprazolam tablets efficiently, without compromising quality forensic standards.     

中国DNA数据库建设应用技术现状及发展趋势

中国的法庭科学DNA数据库建设历经10年,在应用中取得了显著成果.随着DNA分析技术的进步,DNA数据库更加完善,DNA信息作用更加突显.本文综述了中国DNA数据库的规划与建设,DNA数据库建设中的应用技术,以及DNA数据库建设应用技术发展趋势,为完善DNA数据库建设提供借鉴.