Variability of fingerprint ridge density in a sample of Spanish Caucasians and its application to sex determination.

Despite the fact that the differences in epidermal ridge density between men and women have been accepted for some time, they have only been thoroughly demonstrated in a small number of populations. The aim of this study is to determine whether such differences exist in a sample of the Spanish population by counting epidermal ridges within three well-defined fingerprint areas. If significant gender differences do exist, then the likelihood of inferring gender from given ridge densities will be explored. The data used in this study was obtained from all 10 fingerprints of 200 individuals of the Spanish Caucasian population (100 males and 100 females) between the ages of 20 and 30. Results show that women tend to have a significantly higher ridge density than men in the distal region of all 10 fingers (radial and ulnar count areas), but not in the proximal region (lower count area). The application of Bayes' theorem, assuming that prior probabilities known for each sex, indicate a threshold for discrimination of sexes.