Forensic Decision Research Articles

Improving forensic examiner decision-making through deliberate practice.

Forensic examiners make important decisions to address legal questions, yet there is now ample evidence that their decisions can be subjective and inconsistent. This commentary suggests that elements of deliberate practice may help in not only having more consistent forensic decisions but also toward expected accuracy. Specifically, four elements of deliberate practice: (1) setting a goal, (2) motivation, (3) feedback, and (4) repetition are outlined with examples for addressing issues of cognitive bias and managing stress at work. If any of these elements are missing, such as delayed or no feedback, then suboptimal or no improvement of examiners' decision-making may result. This tool for deliberately improving decision-making may be applicable to other legal professionals; thus, potentially driving policies that may help enhance the criminal justice system broadly.

The effects of cognitive bias, examiner expertise, and stimulus material on forensic evidence analysis.

Forensic examiners have come under scrutiny due to high-profile exonerations, highlighting the consequences that contextual bias can have on investigations. Researchers have proposed solutions to reduce the effects of bias including blind testing and redacting task-irrelevant information. Practitioners have concerns over the limitations of some of this research that uses untrained students to examine complex pieces of forensic evidence (e.g., fingerprints) (1; but see 2 for studies including trained experts and/or actual casework). This study sought to (a) examine the effect of contextual bias on examiners' evaluation of forensic evidence by varying the amount of pre-comparison information available to participants, (b) compare student and expert examiners' performance and their vulnerability to contextual bias, and (c) examine the effects of contextual bias on examiners' evaluation of different types of forensic evidence. Expert fingerprint examiners and student participants were presented with varying amounts of pre-comparison case information and compared matching and non-matching fingerprint and footwear impression evidence. Results suggest no effects of blinding examiners from case information or redacting task-irrelevant information. As expected, expert fingerprint examiners were more likely to correctly identify matching fingerprints and correctly exclude non-matching fingerprints than students. However, expert fingerprint examiners were no better than student participants at comparing footwear impression evidence. These findings suggest that sample, stimulus selection, and discipline-specific training matter when investigating bias in forensic decision making. These findings suggest caution when using forensic stimuli with student samples to investigate forensic decision-making and highlight the need for more research on redaction procedures.

Extending the discussion on inconsistency in forensic decisions and results.

The subject of inter- and intra-laboratory inconsistency was recently raised in a commentary by Itiel Dror. We re-visit an inter-laboratory trial, with which some of the authors of this current discussion were associated, to diagnose the causes of any differences in the likelihood ratios (LRs) assigned using probabilistic genotyping software. Some of the variation was due to different decisions that would be made on a case-by-case basis, some due to laboratory policy and would hence differ between laboratories, and the final and smallest part was the run-to-run difference caused by the Monte Carlo aspect of the software used. However, the net variation in LRs was considerable. We believe that most laboratories will self-diagnose the cause of their difference from the majority answer and in some, but not all instances will take corrective action. An inter-laboratory exercise consisting of raw data files for relatively straightforward mixtures, such as two mixtures of three or four persons, would allow laboratories to calibrate their procedures and findings.

Contextual bias by Forensic Document Examination trainees: An empirical study from China

The impact of contextual bias has been repeatedly demonstrated across forensic domains; however, research on this topic in China is scarce. To examine the prevalence of contextual bias in pattern feature-comparison disciplines, we conducted an experiment involving 24 forensic document examination students. The aim was to determine whether knowledge of different contextual information influenced their forensic decision-making. Participants were divided into different context groups and tasked with examining whether questioned signatures with ambiguous features matched reference signatures. The results of independent-samples t-tests for their decision score data in the two context groups exhibited a statistically significant difference (p < 0.05, Cohen’s d > 0.8). Moreover, the submitted forensic reports by participants disclosed a biased evaluation of handwriting features. These findings show how contextual information can bias forensic decision-making in handwriting examination. Context management with complementary strategies such as case triage, cognitive training and decision-making transparency must be implemented to minimize bias in handwriting examination.

Contextual bias in forensic toxicology decisions: A follow-up empirical study from China.

The impact of contextual bias has been demonstrated repeatedly across forensic domains; however, research on this topic in forensic toxicology is very limited. In our previous study, experimental data from only one context version were compared with the actual forensic biasing casework. As a follow-up, this controlled experiment with 159 forensic toxicology practitioners was conducted, to test whether knowledge of different contextual information influenced their forensic decision-making. Participants in different context groups were tasked to identify testing strategies for carbon monoxide and opiate drugs. The results of chi-squared tests for their selections and two context groups exhibited statistically significant differences (p < 0.05 or p < 0.01). These findings show contextual information can bias forensic toxicology decisions about testing strategies, despite it is a relatively objective domain in forensic science.

A guide to measuring expert performance in forensic pattern matching

Decisions in forensic science are often binary. A firearms expert must decide whether a bullet was fired from a particular gun or not. A face comparison expert must decide whether a photograph matches a suspect or not. A fingerprint examiner must decide whether a crime scene fingerprint belongs to a suspect or not. Researchers who study these decisions have therefore quantified expert performance using measurement models derived largely from signal detection theory. Here we demonstrate that the design and measurement choices researchers make can have a dramatic effect on the conclusions drawn about the performance of forensic examiners. We introduce several performance models – proportion correct, diagnosticity ratio, and parametric and non-parametric signal detection measures – and apply them to forensic decisions. We use data from expert and novice fingerprint comparison decisions along with a resampling method to demonstrate how experimental results can change as a function of the task, case materials, and measurement model chosen. We also graphically show how response bias, prevalence, inconclusive responses, floor and ceiling effects, case sampling, and number of trials might affect one’s interpretation of expert performance in forensics. Finally, we discuss several considerations for experimental and diagnostic accuracy studies: (1) include an equal number of same-source and different-source trials; (2) record inconclusive responses separately from forced choices; (3) include a control comparison group; (4) counterbalance or randomly sample trials for each participant; and (5) present as many trials to participants as is practical.

Examination of fire scene reconstructions using virtual reality to enhance forensic decision-making. A case study in Scotland.

When attending a crime scene, first responders are responsible for identifying areas of potential interest for subsequent forensic examination. This information is shared with the police, forensic practitioners, and legal authorities during an initial meeting of all interested parties, which in Scotland is known as a forensic strategy meeting. Swift documentation is fundamental to allow practitioners to learn about the scene(s) and to plan investigative strategies, traditionally relying on word-of-mouth briefings using digital photographs, videos, diagrams, and verbal reports. We suggest that these early and critical briefings can be augmented positively by implementing an end-to-end methodology for indoor 3D reconstruction and successive visualisation through immersive Virtual Reality (VR). The main objective of this paper is to provide an integrative documentation tool to enhance the decision-making processes in the early stages of the investigation. Taking a fire scene as an example, we illustrate a framework for rapid spatial data acquisition of the scene that leverages structure-from-motion photogrammetry. We developed a VR framework that enables the exploration of virtual environments on a standalone, low-cost immersive head-mounted display. The system was tested in a two-phased inter-agency fire investigation exercise, where practitioners were asked to produce hypotheses suitable for forensic strategy meetings by (1) examining traditional documentation and then (2) using a VR walkthrough of the same premises. The integration of VR increased the practitioners’ scene comprehension, improved hypotheses formulation with fewer caveats, and enabled participants to sketch the scene, in contrast to the orientation challenges encountered using conventional documentation.

Do inconclusive forensic decisions disadvantage the innocent?

Two experiments examined the potential for inconclusive forensic decisions to disadvantage the innocent. Both experiments tested the hypothesis that inconclusive decisions produce more incriminating legal judgments than do clearly exculpatory forensic decisions. Experiment 2 also examined whether this hypothesized effect conformed to a confirmation bias, a communication error, or perceptual accuracy. In Experiment 1 (N = 492), a forensic expert testified that physical evidence recovered from a crime scene either matched or did not match a suspect's evidence or produced an inconclusive result. In Experiment 2 (N = 1,002), a forensic expert testified that physical evidence recovered from a crime scene either matched or did not match a suspect's evidence, produced an inconclusive result, or was unsuitable for analysis. A fifth condition omitted the forensic evidence and expert testimony. The inconclusive decision produced less incriminating legal judgments than did the match forensic decision (|d|average = 0.96), more incriminating legal judgments than did the no-match forensic decision (|d|average = 0.62), and equivalent legal judgments to the unsuitable decision (|d|average = 0.12) and to legal judgments made in the absence of forensic evidence (|d|average = 0.07). These results suggest that participants interpreted the inconclusive decision to be forensically neutral, which is consistent with a communication error. The findings provide preliminary support for the idea that inconclusive decisions can put the innocent at risk of wrongful conviction by depriving them of a clearly exculpatory forensic decision. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Supplemental Material for Do Inconclusive Forensic Decisions Disadvantage the Innocent?

Supplemental Material for Do Inconclusive Forensic Decisions Disadvantage the Innocent?

Determining rib fracture age from CT scans with a radiomics-based combined model: a multicenter retrospective study

ObjectivesWe aimed to develop a combined model based on clinical and radiomic features to classify fracture age.MethodsWe included 1219 rib fractures from 239 patients from our center between March 2016 and September 2022. We created an external dataset using 120 rib fractures from 32 patients from another center between October 2019 and August 2023. According to tasks (fracture age between < 3 and ≥ 3 weeks, 3–12, and > 12 weeks), the internal dataset was randomly divided into training and internal test sets. A radiomic model was built using radiomic features. A combined model was constructed using clinical features and radiomic signatures by multivariate logistic regression, visualized as a nomogram. Internal and external test sets were used to validate model performance.ResultsFor classifying fracture age between < 3 and ≥ 3 weeks, the combined model had higher areas under the curve (AUCs) than the radiomic model in the training set (0.915 vs 0.900, p = 0.009), internal test (0.897 vs 0.854, p < 0.001), and external test sets (0.881 vs 0.811, p = 0.003). For classifying fracture age between 3–12 and > 12 weeks, the combined model had higher AUCs than the radiomic model in the training model (0.848 vs 0.837, p = 0.12) and internal test sets (0.818 vs 0.793, p < 0.003). In the external test set, the AUC of the nomogram-assisted radiologist was 0.966.ConclusionThe combined radiomic and clinical model showed good performance and has the potential to assist in the classification of rib fracture age. This will be beneficial for clinical practice and forensic decision-making.Critical relevance statementThis study describes the development of a combined radiomic and clinical model with good performance in the classification of the age of rib fractures, with potential clinical and forensic applications.Key points• Complex factors make it difficult to determine the age of a fracture.• Our model based on radiomic features performed well in classifying fracture age.• Associating the radiomic features with clinical features improved the model’s performance.Graphical

Racial Bias in Forensic Decision Making. Comment on Yim, A.-D.; Passalacqua, N.V. A Systematic Review and Meta-Analysis of the Effects of Race in the Criminal Justice System with Respect to Forensic Science Decision Making: Implications for Forensic Anthropology. Humans 2023, 3, 203–218

A “Systematic Review and Meta-Analysis of the Effects of Race in the Criminal Justice System” [...]

The possible impact of stress on forensic decision-making: An exploratory study

Stress has been shown to have an impact on the quality of decisions made by professionals in a variety of domains. However, there is lack of research examining the impact of stress on forensic decision-making contexts, where experts can face various levels of stress. This exploratory study examines fingerprint decisions made under stress, by novices (N = 115) and fingerprint experts (N = 34). Findings suggested a potentially complex relationship between stress and expert performance. On the one hand, in this study stress seemed to improve the performance of both novices and experts on fingerprint assessments, but mainly for same-source evidence. In contrast, the induced stress appeared to have an impact on risk-taking. When the same-source prints were difficult, a trend emerged with stressed experts taking less risk and reported more inconclusive conclusions with higher confidence than the control group. Furthermore, stress had a significant impact on the overall confidence levels and response times of novices, but not experts. These findings suggest that stress and decision-making tasks are important factors that should be considered when considering optimal working environments for increasing decision quality.

A Systematic Review and Meta-Analysis of the Effects of Race in the Criminal Justice System with Respect to Forensic Science Decision Making: Implications for Forensic Anthropology

Instances of racial disparities are well documented in the United States’ criminal justice system. This study reviewed the literature and conducted quantitative analyses on the role of race in forensic decision making among practitioners and other stakeholders in the criminal justice system. We hypothesized that Black, Indigenous, and People of Color (BIPOC) individuals will be significantly more likely to be associated with adverse outcomes than White individuals. A search strategy was developed and registered before the study commenced. Quantitative data were extracted from eligible studies to estimate the pooled effect size (odds ratio) for the effects of race. A final sample of 11 data sources (published study or dataset) was identified. Decision making by all stakeholders in the criminal justice system, including forensic practitioners, case investigators, and juries were evaluated in these studies. Two datasets evaluated the decision-making process involving forensic psychology or psychiatry, three focused on forensic evidence, four on forensic pathology, one involved forensic anthropology cases, and one involved clinical forensic medicine cases. The pooled odds ratio was estimated to be 1.10 (95% confidence interval: 0.67–1.81), indicating a trivial or negligible effect of race (i.e., BIPOC individuals were no more likely to be associated with adverse outcomes given the current evidence). Importantly, the results of this study do not indicate that bias or disparity related to race does not exist in forensic decision making in the criminal justice system. More research into systemic bias in forensic decision making, especially in relation to race, is needed. Forensic anthropologists are uniquely positioned to study and address racial disparities in the criminal justice system involving forensic science because of its interdisciplinary and multidisciplinary nature. This study highlights the need for further research and advocates for forensic anthropologists to be more involved in the study of the science and the impacts of forensic science rather than focusing on methodological advancement.

Investigation of the variability in the tool marks produced by modified blank firing pistols on fired 7.65 mm projectiles

Firearms identification has an important place in forensic ballistic investigations since the weapons are widely used in criminal offences. Firearm examiners resolve many case files, through the use of automatic systems or comparison microscopes. Advanced forensic technologies like BALİSTİKA helps to record and analyze non standard ballistic evidence. In today's world, with the ease of access to materials and production technique information, pistols modified from blank firers are frequently encountered as crime tools. In this study, the characteristics of 7.65 mm fired cartridge cases obtained by controlled shots from blank firing modified pistols were examined, and their detection performances were compared by means of the Balistika system. Although distinctive differences are not expected after successive test shootings, balistically important changes were seen after the use of blank firing modified pistols and the 3D imaging system proved to be useful in observing such differences. The analyses showed that the modifications in weapons lead to variation in the ballistic characteristics and reduce the accuracy of the detection performance, which may result in flawed forensic decisions. It was also found that the deviations in ballistic impressions of modified blank firing pistols were greater than that of standard fabricated and hand-made pistols. This unique study contributed to the forensic sciences literature by focusing on the impact of modified weapons on ballistic characteristics.

Finding the perfect match: Fingerprint expertise facilitates statistical learning and visual comparison decision-making.

Forensic feature-comparison examiners compare-or "match"-evidence samples (e.g., fingerprints) to provide judgments about the source of the evidence. Research demonstrates that examiners in select disciplines possess expertise in this task by outperforming novices-yet the psychological mechanisms underpinning this expertise are unclear. This article investigates one implicated mechanism: statistical learning, the ability to learn how often things occur in the environment. This ability is likely important in forensic decision-making as samples sharing rarer statistical information are more likely to come from the same source than those sharing more common information. We investigated 46 fingerprint examiners' and 52 novices' statistical learning of fingerprint categories and application of this knowledge in a source-likelihood judgment task. Participants completed four measures of their statistical learning (frequency discrimination judgments, bounded and unbounded frequency estimates, and source-likelihood judgments) before and after familiarization to the "ground-truth" category frequencies. Compared to novices, fingerprint examiners had superior domain-specific statistical learning across all measures-both before and after familiarization. This suggests that fingerprint expertise facilitates domain-specific statistical learning-something that has important theoretical and applied implications for the development of training programs and statistical databases in forensic science. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Comparison between Blood, Non-Blood Fluids and Tissue Specimens for the Analysis of Cannabinoid Metabolites in Cannabis-Related Post-Mortem Cases

Cannabis use is widespread and is one of the most common drugs encountered in forensic-related analysis (antemortem and postmortem cases). However, the correlation between illicit cannabis use and death is rarely investigated, even while taking into consideration its role in the central nervous system depression and cardiovascular disorders. Few studies have discussed other non-blood specimens; this has brought a special interest in analyzing THC and its metabolites in different body parts in order to make precise forensic decisions. Herein, we are investigating the presence of Δ9-tetrahydrocannabinol (THC) and its metabolites:(11-hydroxy-Δ9-tetrahydrocannabinol (THC-OH) and 11-nor-Δ9- tetrahydrocannabinol-9-carboxy (THC-COOH)) in different postmortem specimens. Forty-three cases of bodily fluids and tissue post-mortem samples, previously found to be cannabinoid-positive were analyzed in the current investigation using alkaline hydrolysis followed by solid phase extraction and LC-MS/MS for THC and its metabolites concentration. In the current study, the highest median THC-COOH and THC-OH concentrations were detected in bile samples (1380 ng/mL and 8 ng/mL, respectively), while the highest THC median concentration was detected in gastric contents (48 ng/mL). This can be explained due to the postmortem distribution of blood to other bodily fluids and tissues and the accumulation in bile following multiple doses. Furthermore, high THC levels in gastric contents can be explained by the undergoing cycles of entero-hepatic circulation which resulted in a significant increase in THC in gastric contents. THC-COOH can be the best indicator to detect cannabinoids in toxicology studies, thus the inclusion of active THC metabolites is essential in death investigations. Additionally, THC-OH concentrations in postmortem cases could be influenced by body mass index. In this study, all types were specimens found to be suitable for testing cannabinoid metabolites, except for vitreous humor which showed low rates of detectability for cannabinoid metabolites.

Differences in ballistic findings between autopsy and post-mortem computed tomography in the head and neck region of gunshot victims: a comprehensive synthesis for forensic decision-making.

Differences in ballistic findings between autopsy and post-mortem computed tomography in the head and neck region of gunshot victims: a comprehensive synthesis for forensic decision-making.

Reducing the impact of cognitive bias in decision making: Practical actions for forensic science practitioners

Previously published methods for reducing the impact of cognitive bias in forensic decision making have focused primarily on actions at the laboratory or organizational levels. This paper presents generalized and specific actions that forensic science practitioners can take to reduce the impact of cognitive bias in their work. Practical examples illustrating ways that practitioners can implement many of the specific actions are also provided, along with some suggestions for handling court testimony about cognitive bias. The actions presented in this paper provide a means through which individual practitioners can take ownership for minimizing cognitive bias in their work. Such actions can provide supporting evidence to stakeholders that forensic practitioners acknowledge the existence of cognitive bias and its potential influence on their work, and they can also stimulate implementation of methods that focus on solutions at the laboratory and organizational levels.

Neuropsychological deficits associated with medical conditions: Implications for psychological services in criminal legal settings.

Criminal legal system-involved populations are disproportionally impacted by chronic health conditions relative to the general population. These discrepancies are thought to be due to both health disparities and increased likelihood to engage in health-compromising behaviors. Medical conditions can significantly influence neuropsychological functioning and, in turn, thinking and behavior relevant to clinical forensic decision-making and psychological practice in criminal legal settings. The aim of this article is to review medical conditions commonly observed among system-involved populations-specifically cardiovascular disease, human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), traumatic brain injury, cancer, diabetes, and medication side effects-and describe the complex and important links between these conditions, their associated neuropsychological deficits, and applications to psychological assessment and treatment in criminal legal settings. Ultimately, this discussion will be useful to staff providing psychological services in these settings by increasing their familiarity with these concepts, and providing practical applications to inform their case conceptualization, assessment, and treatment services with system-involved individuals. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

How to make better forensic decisions

Much of forensic practice today involves human decisions about the origins of patterned sensory evidence, such as tool marks and fingerprints discovered at a crime scene. These decisions are made by trained observers who compare the evidential pattern to an exemplar pattern produced by the suspected source of the evidence. The decision consists of a determination as to whether the two patterns are similar enough to have come from the same source. Although forensic pattern comparison disciplines have for decades played a valued role in criminal investigation and prosecution, the extremely high personal and societal costs of failure—the conviction of innocent people—has elicited calls for caution and for the development of better practices. These calls have been heard by the scientific community involved in the study of human information processing, which has begun to offer much-needed perspectives on sensory measurement, discrimination, and classification in a forensic context. Here I draw from a well-established theoretical and empirical approach in sensory science to illustrate the vulnerabilities of contemporary pattern comparison disciplines and to suggest specific strategies for improvement.