Assessment of the methodology for estimating ridge density in fingerprints and its forensic application

Study of the fingerprints of a Spanish sample for the determination of the hand and finger

The individuality and permanence of fingerprints make of them a very useful feature in the identification of individuals. There are now automated computer programmes that allow a quick comparison between a fingermark and a database. However, in order to assess the strength of evidence in fingerprint identification, complementary information on the frequencies of the different morphological features of the dermopapillary ridges is required. This idea is used in this work as a starting point to evaluate the frequencies of the parameters used in the determination of the hand and finger in a large sample of 2600 fingerprints taken from 134 male and 127 female Spanish population. Based on these fingerprints, the frequencies of different categories of the following parameters were obtained: type of pattern, slope of the apex ridge, subtype of two-delta pattern, ridge tracing, major angle, major ridge count, bisector, rotation of the central ridge, assimilation to loops and slant. Moreover, the results have shown that these characters are useful for the determination of the hand in whorls (two-delta pattern) and loops (one-delta pattern), but not for the determination of the finger. The most useful and classificatory parameter when determining the hand of origin of a two-delta fingerprint is the slope of the apex ridge, and for the one-delta pattern, knowing the location of the delta allows the correct estimation of the hand of a fingerprint in more than 93% of the cases. The data presented in this paper are novel and can be used by latent print examiners to improve the statistical basis of their decisions in reaching conclusions.

Interpopulational differences in the frequency and distribution of delta types

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.

Fingerprint evidence for the division of labour and learning pottery-making at Early Bronze Age Tell eṣ-Ṣâfi/Gath, Israel

The organization of craft production has long been a marker for broader social, economic and political changes that accompanied urbanism. The identity of producers who comprised production groups, communities, or workshops is out of reach using conventional archaeological data. There has been some success using epidermal prints on artefacts to identify the age and sex of producers. However, forensic research indicates that a combination of ridge breadth and ridge density would best identify the age and sex of individuals. To this end, we combine mean ridge breadth (MRB) and mean ridge density (MRD) to distinguish the age and sex of 112 fingerprints on Early Bronze Age (EB) III pottery from the early urban neighbourhood at Tell eṣ-Ṣâfi/Gath, Israel, dating to a 100 year time span. Our analysis accounts for the shrinkage of calcareous fabrics used to make six type of vessels, applies a modified version of the Kamp et al. regression equation to the MRB for each individual print, and infers sex by correlating MRD data to appropriate modern reference populations. When the results are combined, our analyses indicate that most fingerprints were made by adult and young males and the remainder by adult and young females. Children’s prints are in evidence but only occur on handles. Multiple prints of different age and sex on the same vessels suggest they were impressed during the training of young potters. Production appears dominated by adult and young males working alone, together, and in cooperation with adult and/or young females. Vessels with prints exclusively by females of any age are rare. This male dominant cooperative labour pattern contrasts recent studies showing that adult women primarily made Neolithic figurines in Anatolia, and more females than males were making pottery prior to the rise of city-states in northern Mesopotamia.

Dermal digital ridge density of a penal population: Analysis of association and individualization

The present study is an attempt to analyze an association between dermal digital ridge density and explosive personality based on the study of 100 male prisoners and 50 controls. The control group had higher ridge density than the prisoners. Bilateral differences revealed higher ridge density on left hand than right hand in both the groups, but differences between two groups for directional asymmetry were not significant. Surface area is not correlated with ridge density in all the digits. About 50% of the variation in ridge density may be explained by a single factor which in all probability is the genetic component of variation. Ridge density cannot be used as a marker for assessing individual's height. Individuals having ridge density less than 12 ridges and higher than 15 ridges, i.e. placed on the two extremes were more likely than not to have more explosive personality.

Topological variability and sex differences in fingerprint ridge density in a sample of the Sudanese population

Fingerprints are important biometric variables that show manifold utilities in human biology, human morphology, anthropology, and genetics. Their role in forensics as a legally admissible tool of identification is well recognized and is based on their stability following full development, individualistic characteristics, easy classification of their patterns, and uniqueness. Nevertheless, fingerprint ridge density and its variability have not been previously studied in the Sudanese population. Hence, this study was conducted to analyze the topological variability in epidermal ridge density and to assess the possibility of its application in determining sex of Sudanese Arabs. The data used for this study were prints of all 10 fingers of 200 Sudanese Arab individuals (100 men and 100 women) aged between 18 and 28 years. Fingerprint ridge density was assessed for three different areas (radial, ulnar and proximal) for all 10 fingers of each subject. Significant variability was found between the areas (p < 0.01). Women showed significantly higher ridge density in the three areas for all and each fingers. Men and women showed similar patterns of densities with distal areas being denser than proximal ones. Side asymmetry was more evident in distal areas. Ridge density thresholds for discrimination of sexes were developed. Hence, fingerprints found in forensic examinations/crime scenes can be useful to determine sex of Sudanese individuals based on fingerprint ridge density; furthermore, ridge density can be considered a morphological trait for individual variation in forensic anthropology.

Fingerprint ridge density in the Argentinean population and its application to sex inference: A comparative study

Fingerprint ridge density (RD) is known to vary according to sex and population, and such variation can be used for forensic purposes. The aim of this study was to analyze the fingerprint RD of two samples of the Argentinean population in order to assess their topological, digital, bilateral, sexual, and population differences for subsequent application in the inference of sex. Data were collected from the fingerprints of 172 individuals from the Buenos Aires province and 163 from the Chubut province. RD was assessed for three different count areas for all 10 fingers of each individual. In both sexes and both samples, significant differences among areas were obtained, so that radial-RD>ulnar-RD>proximal-RD. Females presented greater RD than males in all areas and on all fingers. Regarding population differences, no significant differences were found between the Buenos Aires and Chubut samples (except for proximal RD in males). However, both samples showed RD significantly different from that of the Jujuy province. The application of Bayes' theorem allowed for the identification of an RD threshold for discrimination of sexes in these Argentinean samples. In conclusion females consistently exhibit narrower epidermal ridges than males, which may evidence a universal pattern of sexual dimorphism in this trait that can be useful in forensics in the identification of individuals.

Variability of palmprint ridge density in a North Indian population and its use in inference of sex in forensic examinations

Fingerprints and palmprints are unique to an individual, and these biometric characters are used in the identification of individuals. In the recent past, ridge density (ridge count in a defined area) has been explored for its applicability in inference of sex from the fingerprints and palmprints recovered at the crime scene. The present research aims to study the variability of palmprint ridge density in a North Indian population, and its significance in inference of sex in forensic examinations. The sample consisted of 157 healthy young adults (110 females and 47 males) from Shimla city in North India. Bilateral palmprints were taken from all the participants following standard methods. The palmprints were manually analyzed in four defined areas of each palmprint that included the central prominent part of the thenar eminence (P1), the mount distal to the axial triradius on the hypothenar region (P2), the mount proximal to the triradius of the second digit (P3) and the mount proximal to the triradius of the fifth digit (P4). The ridge density was calculated diagonally using a square measuring 5 mm × 5 mm. The sex differences in palmprint ridge densities were statistically analyzed for each of the designated areas using statistical considerations. Receiver operating characteristic (ROC) curve analysis was done to test the overall ability of the palmprint ridge densities obtained from each area in inference of sex. The mean palmprint ridge density was found to be significantly greater in females than in males in all the four defined areas of the palmprint. Ridge densities in P3 and P4 areas of the palmprint showed statistically significant bilateral differences in both males and females. The study observed variations in the ridge density between the four designated areas of the palmprint. Based on the area under the ROC curve (AUC), maximum sexing potential for the palmprint ridge density was observed in the P4 area, followed by P3 area on both right and left sides. ROC analysis of the total palmprint ridge density indicated that the sexing accuracy from the right and left palmprint ridge densities was 70.2% and 71.8% respectively. The study shows variability of palmprint ridge density among sexes and in different regions of the palm on both sides. In view of the considerable overlapping in male and female values and lower levels of accuracy obtained in ROC analysis, the present research concludes that the palmprint ridge density cannot be used as an effective tool in inference of sex. However, in absence of other more reliable means/evidence, it still can be considered as a supportive trait in sex inference.