Biomechanics of knife stab attacks

In the past it has been assumed that the fingerprints of women tend to have "fine" epidermal ridge detail while men have "coarse" ridge detail. Past studies have examined this hypothesis but have not clearly demonstrated if observed differences are statistically significant. The goal of this study is to determine if women have significantly higher ridge density, hence finer epidermal ridge detail, than men by counting ridges that occur within a well defined space. If significant gender differences do exist then the likelihood of inferring gender from given ridge densities will be explored. This study focused on 400 randomly picked ten-print cards representing 400 subjects. The demographic composition of this sample population represents 100 Caucasian males, 100 African American males, 100 Caucasian females and 100 African American females all within the age range of 18-67. Results show that women tend to have a significantly higher ridge density than men and that this trend is upheld in subjects of both Caucasian and African American descent (F = 81.96, P < 0.001). Application of Bayes' theorem suggests that a given fingerprint possessing a ridge density of 11 ridges/25 mm2 or less is most likely to be of male origin. Likewise a fingerprint having a ridge density of 12 ridges/25 mm2 or greater is most likely to be of female origin, regardless of race.