[Show abstract][Hide abstract] ABSTRACT: For all forensic disciplines dealing with identification -- e.g., of glass, tool marks, fibers, faces, fingers, handwriting, speakers -- in which manual (subjective, nonautomated) processes play a role, operator dependencies are relevant. With respect to earprint identification, in the period 2002-2005, the Forensic Ear Identification research project collected a database of 1229 donors, three prints per ear, and laid down a "best practice" for print acquisition. Repeatability and reproducibility aspects of the print acquisition are tested. The study suggests that different operators may acquire prints of differing quality, with equal error rates of the matching system ranging from 9% to 19%. Moreover, it turns out that "matching" earprints are more alike when taken in a consecutive row than when taken on separate occasions. This underlines the importance of (1) studying operator effects, (2) operator training, and (3) not gathering "matching" reference material at the same occasion.
No preview · Article · Apr 2008 · Journal of Forensic Sciences
[Show abstract][Hide abstract] ABSTRACT: The Forensic Ear Identification (FearID) research project was started in order to study the strength of evidence of earprints found on crime scenes. For this purpose, a sample of earprints from 1229 donors over three countries was collected. From each donor three left and three right earprints were gathered. On the one hand, operators denoted contours of the earprints to facilitate segmentation of the images, on the other anthropological specialists denoted anatomically specific locations. On the basis of this, methods for automated classification were developed and used for training of a system that classifies pairs of prints as 'matching' or 'non-matching'. Comparing lab quality prints, the system has an equal error rate of 4%. Starting from a reference database containing two prints per ear, hitlist behaviour is such that in 90% of all query searches the best hit is in the top 0.1% of the list. The results become less favourable (equal error rate of 9%) for print/mark comparisons.
No preview · Article · Apr 2007 · Forensic Science International
[Show abstract][Hide abstract] ABSTRACT: A problem in forensic facial comparison of images of perpetrators and suspects is that distances between fixed anatomical points in the face, which form a good starting point for objective, anthropometric comparison, vary strongly according to the position and orientation of the camera. In case of a cooperating suspect, a 3D image may be taken using e.g. a laser scanning device. By projecting the 3D image onto a 2D image with the suspect's head in the same pose as that of the perpetrator, using the same focal length and pixel aspect ratio, numerical comparison of (ratios of) distances between fixed points becomes feasible. An experiment was performed in which, starting from two 3D scans and one 2D image of two colleagues, male and female, and using seven fixed anatomical locations in the face, comparisons were made for the matching and non-matching case. Using this method, the non-matching pair cannot be distinguished from the matching pair of faces. Facial expression and resolution of images were all more or less optimal, and the results of the study are not encouraging for the use of anthropometric arguments in the identification process. More research needs to be done though on larger sets of facial comparisons.
No preview · Article · Dec 2006 · Forensic Science International
[Show abstract][Hide abstract] ABSTRACT: As part of the Forensic Ear Identification (FearID) research project, which aims to obtain estimators for the strength of evidence of earmarks found on crime scenes, a large database of earprints (over 1200 donors) has been collected. Starting from a knowledge-based approach where experts add anatomical annotations of minutiae and landmarks present in prints, comparison of pairs of prints is done using the method of Vector Template Matching (VTM). As the annotation process is subjective, a validation experiment was performed to study its stability. Comparing prints on the basis of VTM, it appears that there are interoperator effects, individual operators yielding significantly more consistent results when annotating prints than different operators. The operators being well trained and educated, the observed variation on both clicking frequency and choice of annotation points suggests that implementation of the above is not the best way to go about objectifying earprint comparison. Processes like the above are relevant for any forensic science dealing with identification (e.g., of glass, tool marks, fibers, faces, fingers, handwriting, speakers) where manual (nonautomated) processes play a role. In these cases, results may be operator dependent and the dependencies need to be studied.
No preview · Article · Dec 2006 · Journal of Forensic Sciences