Despite major implications for forensic casework, limited research has been done on investigating secondary transfer of latent fingermarks. Adhesive tapes, such as duct tape, can potentially lift latent fingermarks from other surfaces due to their adhesive properties. This study aimed to investigate the possible secondary transfer between layers of adhesive tape and tape and other substrates (metal and plastic). Fingermarks were directly placed onto a primary substrate and subsequently brought into contact with a secondary substrate for varying duration. After visualization, the quality of the fingermarks was assessed to measure their loss and transfer. It was shown that fresh latent fingermarks can transfer between layers of adhesive tape, with instances of sufficient quality for comparison of the transferred fingermarks. In contrast, no transfer was detected after one week. However, a substantial loss of quality of the initially deposited fingermark was observed, suggesting an influence of time. Overall, it was shown that secondary transfer is possible and that caution has to be taken when analysing and interpreting latent fingermarks on adhesive tapes.
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In this paper, we describe a promising method to evaluate the location of fingermarks on two-dimensional objects, which provides valuable information for the evaluation of fingermarks at activity level. For this purpose, an experiment with pillowcases was conducted at the Dutch music festival Lowlands, to test whether the activity ‘smothering’ can be distinguished from an alternative activity like ‘changing a pillowcase’ based on the touch traces on pillowcases left by the activities. Participants performed two activities with paint on their hands: smothering a victim with the use of a pillow and changing a pillowcase of a pillow. The pillowcases were photographed and translated into grid representations. A binary classification model was used to classify the pillowcases into one of the two classes of smothering and changing, based on the distance between the grid representations. After applying the fitted model to a test set, we obtained an accuracy of 98.8%. The model showed that the pillowcases could be well separated into the two classes of smothering and changing, based on the location of the fingermarks. The proposed method can be applied to fingermark traces on all two-dimensional items for which we expect that different activities will lead to different fingermark locations.
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Bayesian networks have shown to be a useful tool for the evaluation of forensic findings given activity level propositions. In this paper, we demonstrate how case specific experiments can be used to assign probabilities to the states of the nodes of a Bayesian network for the evaluation of fingermarks given activity level propositions. The transfer, persistence and recovery of fingermarks on knives is studied in experiments where a knife is either used to stab a victim or to cut food, representing the activities that were disputed in the case of the murder of Meredith Kercher. Two Bayesian networks are constructed, exploring the effect of different uses of the experimental data by assigning the probabilities based on the results of the experiments. The evaluation of the findings using the Bayesian networks demonstrates the potential for fingermarks in addressing activity level propositions.
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