Interpopulational differences in the frequency and distribution of delta types

Abstract The classification of the main pattern types, arch, loop and whorls, is based on the number and location of deltas or triradii, which are areas defined by the confluence of three ridge systems carrying different directions on the fingerprint. Despite being areas that give place to an important morphological variability, their study has only been approached from the quantitative point of view, in relation to the number with which they appear per finger, hand, or individual (intensity pattern), and their sexual and population differences; while the qualitative aspects have not been evaluated so far. The following paper aims to study and analyze the qualitative variability, both intra and interpopulation, of the frequency of occurrence of the different types of deltas or triradii, in four fingerprint samples from males of different population origin: 100 individuals from China, 100 individuals from Colombia, 100 individuals from Nigeria and 100 individuals from Romania, which has meant the analysis of 4000 fingerprints. For this purpose, the classification of 24 types used by the Scientific Police and Criminalist Departments of the Guardia Civil of Spain has been employed. The results obtained showed the non-equiprobability of the frequency distribution of the different delta types in the four populations. In all cases, sunk open total deltas (Hat), sunk open total with point (Hat(p)) and tripod long (Tl) were the most frequent types, while the sunk closed total with point (Hct(p)) had the lowest frequency. Furthermore, for the first time, interpopulation differences in the frequency distribution of different types of deltas have become noticeable. The data provided in this paper are a pioneer in the field of dactyloscopy and can be used as a reference by the departments of criminalistics of the different countries for the estimation of the scientific value of the evidence in dactyloscopy.