There appears to be some hesitation within the forensic biology community to formally evaluate and report on findings given activity level propositions. This hesitance in part stems from concerns about the lack of relevant data on the dynamics of biological traces and doubt about the relevance of such expert opinions to the trier of fact. At the Netherlands Forensic Institute formal evaluative opinions on the probability of case findings given propositions at the activity level are provided since 2013, if requested by a mandating authority. In this study we share the results from a retrospective analysis of 74 of such requests. We explore which party initiates requests, the types of cases that are submitted, the sources of data being used to assign probabilities to DNA transfer, persistence, prevalence and recovery (TPPR) events, the conclusions that were drawn by the scientists, and how the conclusions were used by the courts. This retrospective analysis of cases demonstrates that published sources of data are generally available and can be used to address DNA TPPR events in most cases, although significant gaps still remain. The study furthermore shows that reporting on forensic biology findings given activity level propositions has been generally accepted by the district and appeal courts, as well as the other parties in the criminal justice system in the Netherlands.
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.
Forensic and behavioural science are often seen as two different disciplines. However, there is a growing realization that the two disciplines should be more strongly integrated. Incorporating psychological theories on human behaviour in forensic science could help solving investigative problems, especially at the crime scene. At the crime scene it is not just about applying scientific methods to analyse traces; these traces must first be perceived and categorized as relevant. At the crime scene, the behavioural perspective of an investigative psychologist could play an important role. In this study, we examine to what extent (1) investigative psychologists detect deviant behavioural cues compared to forensic examiners when investigating a crime scene, (2) forensic examiners can find the relevant traces that can be associated with this behaviour and (3) the availability of a psychological report highlighting these behavioural cues helps forensic examiners in finding more relevant traces. To this end, a total of 14 investigative psychologists and 40 forensic examiners investigated a virtual 3D mock crime scene. The results of this study show that investigative psychologists see significantly more deviant behavioural cues than forensic examiners, and that forensic examiners who receive a psychological report on these cues recognize and collect significantly more traces that can be linked to deviant behaviour and have a high evidential value than examiners who did not receive this information. However, the study also demonstrates that behavioural information is likely to be ignored when it contradicts existing beliefs.
