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Abstract Sampling strategy is one of the deciding factors in DNA typing success rates. Small amounts of bodily fluid traces and (skin) contact traces are currently not visualized in standard forensic practice. Trace recovery is usually based on the information available in a particular case and on the experience and 'forensic common sense' applied by the trace recovery expert. Interactions between an offender and a victim may have characteristic features, resulting in specific trace patterns. Understanding these interactions, and their resulting trace patterns, might improve crime related trace recovery as well as DNA typing success rates. In this study, we examined the interactions between offender and victim when a body has been relocated from one position/location to another. The contact between the hands of the offender and the body of the victim was visualized using a fluorescent dye in a lotion that was applied to the hands of the individual undertaking the relocation. The contact locations were scored and patterns were analyzed based on both victim and offender characteristics (height, weight, age, gender). The resulting patterns were compared to current trace recovery practices in the Netherlands. The results of this large-scale study facilitate evidence-based sampling supporting both investigative and evaluative forensic examinations. Highlights • Re-enactment of criminal activity by over 700 participants • Patterns of traces left by offenders are visualized and analyzed. • Evidence based targeting of sampling locations may increase DNA typing success rate. [ABSTRACT FROM AUTHOR]

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)., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Chartered Society of Forensic Sciences. Published by Elsevier B.V. All rights reserved.)