How Cross‐Examination on Subjectivity and Bias Affects Jurors’ Evaluations of Forensic Science Evidence

Contextual bias has been widely discussed as a possible problem in forensic science. The trial simulation experiment reported here examined reactions of jurors at a county courthouse to cross‐examination and arguments about contextual bias in a hypothetical case. We varied whether the key prosecution witness (a forensic odontologist) was cross‐examined about the subjectivity of his interpretations and about his exposure to potentially biasing task‐irrelevant information. Jurors found the expert less credible and were less likely to convict when the expert admitted that his interpretation rested on subjective judgment, and when he admitted having been exposed to potentially biasing task‐irrelevant contextual information (relative to when these issues were not raised by the lawyers). The findings suggest, however, that forensic scientists can immunize themselves against such challenges and maximize the weight jurors give their evidence by adopting context management procedures that blind them to task‐irrelevant information.     

Subjectivity and bias in forensic DNA mixture interpretation

The objectivity of forensic science decision making has received increased attention and scrutiny. However, there are only a few published studies experimentally addressing the potential for contextual bias. Because of the esteem of DNA evidence, it is important to study and assess the impact of subjectivity and bias on DNA mixture interpretation. The study reported here presents empirical data suggesting that DNA mixture interpretation is subjective. When 17 North American expert DNA examiners were asked for their interpretation of data from an adjudicated criminal case in that jurisdiction, they produced inconsistent interpretations. Furthermore, the majority of 'context free' experts disagreed with the laboratory's pre-trial conclusions, suggesting that the extraneous context of the criminal case may have influenced the interpretation of the DNA evidence, thereby showing a biasing effect of contextual information in DNA mixture interpretation.     

Cognitive bias in forensic anthropology: Visual assessment of skeletal remains is susceptible to confirmation bias

An experimental study was designed to examine cognitive biases within forensic anthropological non-metric methods in assessing sex, ancestry and age at death. To investigate examiner interpretation, forty-one non-novice participants were semi randomly divided into three groups. Prior to conducting the assessment of the skeletal remains, two of the groups were given different extraneous contextual information regarding the sex, ancestry and age at death of the individual. The third group acted as a control group with no extraneous contextual information. The experiment was designed to investigate if the interpretation and conclusions of the skeletal remains would differ amongst participants within the three groups, and to assess whether the examiners would confirm or disagree with the given extraneous context when establishing a biological profile. The results revealed a significant biasing effect within the three groups, demonstrating a strong confirmation bias in the assessment of sex, ancestry and age at death. In assessment of sex, 31% of the participants in the control group concluded that the skeleton remains were male. In contrast, in the group that received contextual information that the remains were male, 72% concluded that the remains were male, and in the participant group where the context was that the remains were of a female, 0% of the participants concluded that the remains were male. Comparable results showing bias were found in assessing ancestry and age at death. These data demonstrate that cognitive bias can impact forensic anthropological non-metric methods on skeletal remains and affects the interpretation and conclusions of the forensic scientists. This empirical study is a step in establishing an evidence base approach for dealing with cognitive issues in forensic anthropological assessments, so as to enhance this valuable forensic science discipline.     

The Power of Contextual Effects in Forensic Anthropology: A Study of Biasability in the Visual Interpretations of Trauma Analysis on Skeletal Remains

The potential for contextual information to bias assessments in the forensic sciences has been demonstrated, in several forensic disiplines. In this paper, biasability potential within forensic anthropology was examined by analyzing the effects of external manipulations on judgments and decision‐making in visual trauma assessment. Three separate websites were created containing fourteen identical images. Participants were randomly assigned to one website. Each website provided different contextual information, to assess variation of interpretation of the same images between contexts. The results indicated a higher scoring of trauma identification responses for the Mass grave context. Furthermore, a significant biasing effect was detected in the interpretation of four images. Less experienced participants were more likely to indicate presence of trauma. This research demonstrates bias impact in forensic anthropological trauma assessments and highlights the importance of recognizing and limiting cognitive vulnerabilities that forensic anthropologists might bring to the analysis.     

What do forensic analysts consider relevant to their decision making?

In response to research demonstrating that irrelevant contextual information can bias forensic science analyses, authorities have increasingly urged laboratories to limit analysts' access to irrelevant and potentially biasing information (Dror and Cole (2010) [3]; National Academy of Sciences (2009) [18]; President's Council of Advisors on Science and Technology (2016) [22]; UK Forensic Science Regulator (2015) [26]). However, a great challenge in implementing this reform is determining which information is task-relevant and which is task-irrelevant. In the current study, we surveyed 183 forensic analysts to examine what they consider relevant versus irrelevant in their forensic analyses. Results revealed that analysts generally do not regard information regarding the suspect or victim as essential to their analytic tasks. However, there was significant variability among analysts within and between disciplines. Findings suggest that forensic science disciplines need to agree on what they regard as task-relevant before context management procedures can be properly implemented. The lack of consensus about what is relevant information not only leaves room for biasing information, but also reveals foundational gaps in what analysts consider crucial in forensic decision making.     

The forensic examination of structural fires in Victoria,Australia: Decision-making processes and impact on judicial outcomes

There is a body of published research that has evaluated the contribution of forensic science to the criminal justice system, but many disciplines of forensic science remain unexplored in this regard. The aim of this study was to examine the contribution that forensic fire examination services provide to criminal investigations and court processes in arson cases. Forensic fire examination services differ in a number of ways to the disciplines covered in previous research on the impact of forensic evidence on justice outcomes. Forensic fire examinations involve a combination of scene examination and laboratory analyses, and the results can provide critical evidence of whether an incident that has occurred is a criminal offence (i.e. whether a fire has occurred as the result of an act of arson). Forensic fire examination is also a discipline that has faced challenges and undergone development in recent decades regarding its scientific basis and the issue of contextual bias. In this study, data were collated for 273 structural fires that were examined by the forensic fire services in Victoria, Australia. In this jurisdiction, scene and laboratory forensic services are delivered within short time frames with a focus on providing impartial scientific and investigative services to assist criminal investigations conducted by police. The current dataset was highly skewed in terms of criminal justice outcomes and was not suitable for conducting the planned statistical analyses. Nonetheless, the pattern of findings obtained suggested that the inclusion of forensic evidence which supported the prosecution of arson may be associated with an increased likelihood of suspects being charged and defendants found guilty. Examination of the decision-making process of the forensic fire examiners has provided insight into the variety of evidence that is considered by forensic experts in reaching the important conclusion about the origin and cause of structural fires.     

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.     

Development of a searchable major and trace element database for use in forensic soil comparisons

Forensic soil comparisons are normally undertaken on the basis of several physical, chemical and biological properties, but in all cases the interpretation of results is dependent on the availability of relevant contextual information. This paper summarises the results of major and trace element analyses performed using inductively coupled plasma atomic emission spectrometry and inductively coupled plasma-mass spectrometry on the < 150 µm size fraction of 1896 soil samples collected in connection with forensic investigations in England and Wales between 1999 and 2007. A number of new methods are described which facilitate inter-sample comparison. Although the available data do not provide uniform geographical coverage they do provide useful information which can assist police search investigations and they provide valuable contextual information which aids the evidential assessment of soil evidence when used in court. There is considerable scope to improve the database by increasing the geographical coverage and increasing the number of soil attributes which are included.     

Australian forensic textile damage examinations – Finding a way forward since PCAST

Textile damage examinations are requested in a range of crime types such as assault, sexual assault and homicide. They typically involve the examination of clothing for damage such as cut, tear or thermal damage, often then followed by experimental scenario testing to help ascertain the cause of the damage. Understanding the underpinning science is central to the accurate interpretation of the complex mechanism of damage formation. In a stabbing incident for example, an understanding of the dynamic relationship between the knife blade, fabric and skin (or skin simulant) is critical.Recent reports, including the President's Council of Advisors on Science and Technology (PCAST) report, have scrutinised forensic feature-based comparison techniques. Whilst textile damage was not a focus area, it can be considered a feature-based evidence class, and one which is currently largely reliant upon a practitioner's opinion, experience and professional judgement.This paper will review the current state of textile damage examinations in Australia and survey research being conducted to address the issues raised in the context of the PCAST report. The central contribution of observational data to the evidence class of textile damage will also be explored, as well as some practical measures to counter the effects of cognitive bias.     

Forensic Significance of Gunshot Impact Marks on Inanimate Objects: The Need for Translational Research

Wherever an impact mark is found, either on the surface or on the recovered projectile, it is important for forensic investigators to extract useful information in solving shooting-related cases. This article reviews a collection of works on examination of impact marks upon striking of projectiles on inanimate objects, emphasizing on the retrievable information from a shooting scene and their forensic significance in shooting event reconstruction. Literature suggested that impact marks on target surfaces and the degree of deformation on striking projectiles vary according to different combinations of ammunition and surface materials. It was noted that conditions in real-case scenarios further differed unpredictably in comparison with controlled studies, where forensic investigation should be treated as case-specific basis. Furthermore, the way forensic science is researched and applied operationally has to be reconsidered to reduce the gap via translational approach for more effective use of forensic evidence.     

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.     

Identification of some factors influencing soil transfer on shoes

In criminal activities, soil can be transferred from a crime scene to items linked with a perpetrator; for example, shoes, cars or tools. Several parameters will influence the quantity of soil transferred in a given scenario. The knowledge of the most influential factors can help the expert to assess the evidence using a logical approach at the activity level or to predict the amount of soil that can be expected in a given scenario. The influence of five chosen parameters, namely the shoe profile, shoe size, walker's weight, soil type and soil humidity were assessed using Design of Experiment (DOE) in order to understand their influence on soil quantity transferred on shoes.The Faced Central Composite Design (FCCD) using a quadratic model was found to be highly significant, thus they could be adequately used to model and to interpret the amount of soil recovered from one shoe.These designs demonstrate that the characteristics of the donor (soil type and soil humidity), as well as a combination of these two factors have a very significant impact on the soil transfer. The characteristics of the receptor (shoe profile, shoe size and walker's weight) also have an impact on the transfer but to a lesser extent.Globally, this research provides valuable information for the forensic scientist both in investigative mode: evaluation of the soil quantity possibly transferred on shoes, and in the evaluative steps: is the quantity of soil found on the suspect shoes in accordance to the proposition/scenario given by the prosecution and the defence?     

A Forensic Exploration of the Microsoft Windows 10 Timeline

The Microsoft Windows operating system continues to dominate the desktop computing market. With such high levels of usage comes an inferred likelihood of digital forensic practitioners encountering this platform during their investigations. As part of any forensic examination of a digital device, operating system artifacts, which support the identification and understanding of how a user has behaved on their system provide a potential source of evidence. Now, following Microsoft's April 2018 build 1803 release with its incorporated “Timeline” feature, the potential for identifying and tracking user activity has increased. This work provides a timely examination of the Windows 10 Timeline feature demonstrating the ability to recover activity‐based content from within its stored database log files. Examination results and underpinning experimental methodologies are offered, demonstrating the ability to recover activity tile and process information in conjunction with the Windows Timeline. Further, an SQL query has been provided to support the interpretation of data stored within the ActivitiesCache.db .     

Legal aspects of sexual violence—Does forensic evidence make a difference?

A survey was done of 307 alleged victims of sexual violence reported to the police departments in Greater Aarhus, Denmark, in 1999–2004. The legal disposition was ascertained and related to victim and assault characteristics together with the forensic medical and laboratory findings. The police pressed charges in more than half of the cases and 11% turned out to be false allegations. Nineteen percent of all cases ended with sentencing of the defendant. Sperm was detected in 35% of the examined and analysed cases, and in 46% consumption of alcohol prior to the assault was reported. Information in the forensic report regarding injury documentation, intoxication, and detection of sperm and DNA match between victim and alleged assailant did not aid in the prosecution of the case. Severe coercion used by the assailant increased the likelihood of conviction. Intoxication estimation and sperm detection suffered from low sensitivity compared with laboratory analyses. Results suggest the need for new research and optimising the sexual assault examination protocol to strengthen the legal impact of forensic evidence.     

Evaluation of postmortem biochemical markers: Completeness of data and assessment of implication in the field

Throughout the years an increase has been observed in research output on biochemical markers for determining the postmortem interval (PMI). However, to date, a complete overview is missing on the results of postmortem biochemical markers (PBM's) for PMI estimation. In this paper, literature was reviewed in order to identify the knowledge lacunae of PBM research from a practical point of view. A three-step approach was undertaken in order to achieve the set goal. Literature was collected, the PBM's were evaluated for completeness by means of a scorings index based on set criteria, and PBM's were subsequently evaluated in light of the Daubert & Frye criteria for scientific evidence in court. Seven PBM's were found to be well investigated, from which potassium had the highest completion score. However, none of these PBM's could be qualified as suitable for court evidence. Further, this study revealed that the majority of PBM's (94%) is not well investigated. Consequently, these PBM's did not meet Daubert & Frye criteria. In order to improve the assessment for use of PBM's as evidence in court regarding PMI estimation, PBM's should be investigated more thoroughly and data should be made readily available.     

Sensory information in children’s statements of sexual abuse

The credibility of children’s statements of sexual abuse is a controversial issue in forensic psychiatry and psychology. Neurobiological and clinical laboratory studies show that real memories contain more information regarding sensory details than false memories. The goal of the present field study was to evaluate whether sensory information was present in children’s statements of sexual abuse, and whether this information was more often present in credible statements compared with non-credible statements. Sensory details were extracted from a sample of 96 statements of sexual abuse from children; 62 statements were considered credible and 34 statements were considered non-credible. This study showed that sensory information was present in 79% of children’s reports of child sexual abuse. Sensory information was significantly more often present in statements considered credible compared with non-credible statements (85.5%, P < 0.001), but there were large variations in the sense involved. Logistic regression analysis showed that the presence of at least one sensory detail may be a good predictor of credibility (odds ratio, OR = 23.484, P < 0.05). It seems appropriate to include sensory details when assessing the credibility of children’s statements of child sexual abuse, but it has not yet been demonstrated that use of such details significantly improves the validity of credibility assessments.KEYWORDS: Forensic sciences, forensic psychiatry, forensic psychology, credibility, sensory information, children’s statements, sexual abuse     

Context effects in forensic science: a review and application of the science of science to crime laboratory practice in the United States.

This article discusses the phenomenon of "context effects" by reviewing the findings and practices of a range of scientific fields, including astronomy, physics, biology, medicine, and especially the relevant research and theory from psychology. Context information, such as expectations about what one is supposed to see or conclude, has been found to have a small but relentless impact on human perception, judgment, and decision-making. The article then considers the vulnerability of forensic science practice to context effects, and concludes by suggesting that forensic science adopt practices familiar in other fields of scientific work, in particular blind or double-blind testing and also the use of evidence line-ups.     

The Testimony of Forensic Identification Science: What Expert Witnesses Say and What Factfinders Hear

This research examined how variations in the presentation of forensic science information affect factfinders’ judgments in a trial. Participants read a summary of a murder case, the critical testimony being the results of a microscopic hair comparison given by a forensic expert. Across two experiments we manipulated how the expert expressed his results, whether he gave an explicit conclusion concerning identity of the hair, and whether the limitations of forensic science were expressed during trial. Qualitative testimony was more damaging to the defense than quantitative testimony, conclusion testimony increased the defendant’s culpability ratings when findings were presented quantitatively, and expressing limitations of forensic science had no appreciable effect. Results are discussed in terms of factfinders’ interpretation of forensic identification evidence.