In this case study, we want to gain insights into how residents of three municipalities communicate about the new murder scenario of the cold case of Marianne Vaatstra and the possibility of a large-scale DNA familial searching. We investigate how stakeholders shape their arguments in conversation with each other and with the police. We investigate the repertoires that participants use to achieve certain effects in their interactions with others in three focus groups. The results show that the analyzed repertoires are strong normative orientated. We see two aspects emerge that affect the support for large-scale DNA familial searching. These are: 1. Cautious formulations: respondents showed restraint in making personal judgments and often formulated these on behalf of others. Participants would not fully express themselves, but adjusted to what seemed the socially desirable course. 2. Collective identity: respondents focused on the similarities between themselves and the needs, interests, and goals of other participants. Participants also tried in a discursive way to convince each other to participate in the large-scale familial searching. These two major discursive activities offered the communication discipline guidance for interventions into the subsequent communication strategy.
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In sexual assault cases, the retrieved DNA quantity and sampling location from the victim’s underwear may provide valuable information for activity level evaluative reporting. DNA can transfer from site to site on an exhibit, or be lost within packaging, complicating interpretation. Experiments are needed to investigate these factors. This preliminary study compared two cleaning methods to prepare undergarments for such experimentation: hand-washing with warm water and washing with bleach before rinsing. Results show a significantly lower quantity of DNA on washed underwear using both methods. Warm-water hand-washing, the more straightforward method, was selected for further experimentation.
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.
