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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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.
In cases of sexual assault, the interpretation of biological traces on clothing, and particularly undergarments, may be complex. This is especially so when the complainant and defendant interact socially, for instance as (ex-)partners or by co-habitation. Here we present the results from a study where latent male DNA on female worn undergarments is recovered in four groups with different levels of male-female social interaction. The results conform to prior expectation, in that less interaction tend to result in less male DNA on undergarments. We explore the use of these experimental data for evaluative reporting given activity level propositions in a mock case scenario. We show how the selection of different populations to represent the social interaction between complainant and defendant may affect the strength of the evidence. We further show how datasets of limited size can be used for robust activity level evaluative reporting.
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