Individualization of earprints : Variation in prints of monozygotic twins.

This article presents a study of the variation in the appearance of earprints from six pairs of monozygotic (MZ) twins, applying different methods with varying degrees of objectivity. By analyzing prints of MZ twins, we purposely select pairs of individuals for whom the degree of interindividual variation is low. We first provide an account of the corresponding characteristics and the differences that occur between prints from the individual members. We evaluate differences in both content (i.e., presence, shape, and intensity of imprinted features) and geometry (i.e., position of imprinted features). Differences are visualized by way of digital overlays. Differences in geometry are further evaluated by performing a hierarchical cluster analysis using variables derived from the position of seemingly corresponding features. As a next step, we explore a method to fully automatically analyze prints. In this approach, image regions are selected and matched automatically. A suggestion on how to apply this method to calculate the evidential value of an earprint is provided. To our knowledge, this is the first time that any method capable of fully automated earprint comparisons has been presented in the literature.

Earprints in forensic investigations.

This article provides an overview of the theoretical and practical issues surrounding the use of earprints in forensic research. In the first section, we provide a limited account of the history of earprints in forensic investigations and their use as evidence in court. Criticism of the use of earprints for individualization is addressed and fundamental questions that require attention are summarized. In the second section, we summarize the results of various studies that we have performed on earprint variation. Potential causes of intraindividual variation in earprint appearance are, for instance, variations in the way the prints are lifted, variations in the time the donor spends listening, and variations in the force that is applied during listening. Concerning the latter, we have explored various factors that could influence applied force. We have also studied changes in the morphology of live ears during adulthood.