The findings from a bloodstain pattern analysis (BPA) may assist in formulating or falsifying scenarios that are considered in the investigative stages of a criminal investigation. When a case proceeds to trial the bloodstain pattern expert may be asked about the relevance of their findings given scenarios that are proposed by the prosecution and defense counsel. Such opinions provided by an expert are highly relevant to police investigation or legal proceedings, but the reasoning behind the opinion or implicit assumptions made by the expert may not be transparent.A proper framework for the evaluation of forensic findings has been developed since the late twentieth century, based on the hierarchy of propositions, Bayesian reasoning and a model for case assessment and interpretation. This framework, when implemented in casework, mitigates some of the risks of cognitive biases, and makes the reasoning and scientific basis for the opinion transparent. This framework is broadly used across forensic science disciplines. In this paper we describe its application to the field of BPA using a case example from the Netherlands Forensic Institute (NFI).
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Accurate and reliable decision-making in the criminal justice system depends on accurate expert reporting and on the correct interpretation of evidence by the judges, prosecutors, and defense lawyers. The present study aims to gain insight into the judiciary's capability to assess the accuracy and reliability of forensic expert reports by first examining the extent to which criminal justice professionals are able to differentiate between an accurate (or sound) expert report and an inaccurate (or unsound) expert report. In an online questionnaire, 133 participants assessed both a sound and an unsound expert report. The findings show that, on average, participants were unable to significantly distinguish between sound and unsound forensic expert reports. Second, the study explored the influence of institutional authority on the evaluation of forensic expert reports. Reports that were not recognized as flawed—particularly those originating from well-known and reputable institutions—were subjected to less critical examination, increasing the risk of evaluation errors. These results suggest that the perceived institutional authority influences the assessment of forensic evidence. The study highlights the need for tools to support criminal justice professionals in evaluating forensic evidence, particularly when experts are unregistered. Recommendations include adhering to established quality standards, consulting counter-expert evaluations, improving courtroom communication, and enhancing forensic knowledge through training. Overall, the findings underscore the importance of critical evidence evaluation to reduce the risk of misinterpretation and wrongful convictions in the judicial process.
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Currently, promising new tools are under development that will enable crime scene investigators to analyze fingerprints or DNA-traces at the crime scene. While these technologies could help to find a perpetrator early in the investigation, they may also strengthen confirmation bias when an incorrect scenario directs the investigation this early. In this study, 40 experienced Crime scene investigators (CSIs) investigated a mock crime scene to study the influence of rapid identification technologies on the investigation. This initial study shows that receiving identification information during the investigation results in more accurate scenarios. CSIs in general are not as much reconstructing the event that took place, but rather have a “who done it routine.” Their focus is on finding perpetrator traces with the risk of missing important information at the start of the investigation. Furthermore, identification information was mostly integrated in their final scenarios when the results of the analysis matched their expectations. CSIs have the tendency to look for confirmation, but the technology has no influence on this tendency. CSIs should be made aware of the risks of this strategy as important offender information could be missed or innocent people could be wrongfully accused.
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