Zoekresultaten

A study into evaluating the location of fingermarks on letters given activity level propositions

A previous paper published in this journal proposed a model for evaluating the location of fingermarks on two-dimensional items (de Ronde, van Aken, de Puit and de Poot (2019)). In this paper, we apply the proposed model to a dataset consisting of letters to test whether the activity of writing a letter can be distinguished from the alternative activity of reading a letter based on the location of the fingermarks on the letters. An experiment was conducted in which participants were asked to read a letter and write a letter as separate activities on A4- and A5-sized papers. The fingermarks on the letters were visualized, and the resulting images were transformed into grid representations. A binary classification model was used to classify the letters into the activities of reading and writing based on the location of the fingermarks in the grid representations. Furthermore, the limitations of the model were studied by testing the influence of the length of the letter, the right- or left-handedness of the donor and the size of the paper with an additional activity of folding the paper. The results show that the model can predict the activities of reading or writing a letter based on the fingermark locations on A4-sized letters of right-handed donors with 98 % accuracy. Additionally, the length of the written letter and the handedness of the donor did not influence the performance of the classification model. Changing the size of the letters and adding an activity of folding the paper after writing on it decreased the model’s accuracy. Expanding the training set with part of this new set had a positive influence on the model’s accuracy. The results demonstrate that the model proposed by de Ronde, van Aken, de Puit and de Poot (2019) can indeed be applied to other two-dimensional items on which the disputed activities would be expected to lead to different fingermark locations. Moreover, we show that the location of fingermarks on letters provides valuable information about the activity that is carried out.

Secondary transfer of latent fingermarks by adhesive tape

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.

A study into fingermarks at activity level on pillowcases

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.

Fingermarks beyond the source

fingerprints are a commonly exploited type of evidence and can be crucial in a criminal investigation. The process of individualization or exclusion of a donor relies on the comparison of ridge detail characteristics between a fingermark, found at a crime scene, and reference fingerprints, collected under controlled conditions (either or not stored in a database). Although this process has been successfully used for over a century, fingermarks found at a crime scene are of limited value for a criminal trial if the corresponding reference fingerprint is not available, or the found fingermark is of poor quality. Fingerprints consist of donor secretion, mainly eccrine and sebaceous, of which the exact composition is likely influenced by many (both endogenous and exogenous) factors, including donor traits, habits and activities. Analysis of the chemical composition could thus potentially lead to the retrieval of donor information from those fingerprints that yielded no information in the traditional comparison process. The main aim of this dissertation was to determine what donor information can reliably and validly be derived from the chemical analysis of the fingerprint composition, in order to be used in forensic investigations...

Loss and relocation of DNA and fingermarks during packaging and transport of forensic exhibits

Specific fluorescent signatures for body fluid identification using fluorescence spectroscopy

Non-invasive, rapid, on-site detection and identification of body fluids is highly desired in forensic investigations. The use of fluorescence-based methods for body fluid identification, have so far remain relatively unexplored. As such, the fluorescent properties of semen, serum, urine, saliva and fingermarks over time were investigated, by means of fluorescence spectroscopy, to identify specific fluorescent signatures for body fluid identification. The samples were excited at 81 different excitation wavelengths ranging from 200 to 600 nm and for each excitation wavelength the emission was recorded between 220 and 700 nm. Subsequently, the total emitted fluorescence intensities of specific fluorescent signatures in the UV–visible range were summed and principal component analysis was performed to cluster the body fluids. Three combinations of four principal components allowed specific clustering of the body fluids, except for fingermarks. Blind testing showed that 71.4% of the unknown samples could be correctly identified. This pilot study shows that the fluorescent behavior of ageing body fluids can be used as a new non-invasive tool for body fluid identification, which can improve the current guidelines for the detection of body fluids in forensic practice and provide the robustness of methods that rely on fluorescence.