A study of fingerprint ridge density amongst young adults of north India– sexual dimorphism and forensic aspects

Abstract Background Fingerprint analysis constitutes a fundamental component of forensic investigation. Friction skin ridges are highly reliable for human identification because they are distinctive and permanent, making them helpful in criminal investigations for identifying suspects and victims. The present study aims to evaluate sexual dimorphism on the basis of fingerprint ridge density (FPRD) and study its variability in the radial, ulnar and proximal areas of fingerprints of both left and right hands in males and females. Methods The fingerprints were obtained from all the 10 fingers of 113 individuals from North Indian population (56 males and 57 females) between the ages of 18 and 30 years. Following the fingerprint collection process, the data was manually inspected by counting the ridges in three topological regions of the skin i.e. radial, ulnar, and proximal areas using a linen tester. Subsequently, statistical analysis was employed. The student t-test (parametric) and Mann-Whitney U test (non-parametric) were used to statistically assess the fingerprint ridge density between the sexes in the three topological regions. Further, Bonferroni correction was applied to control for Type I error due to multiple comparisons, and Cohen’s d and Cliff’s delta were calculated to assess the magnitude of sexual dimorphism between males and females. Results and conclusions Females exhibited higher ridge density values than males across all regions. After Bonferroni correction (α = 0.00167), only strongly significant variables remained. Cohen’s d and Cliff’s delta indicated moderate to large sexual dimorphism in several regions, with the large effect size observed in RMR (Right Middle Radial), RMP (Right Middle Proximal), LTR (Left Thumb Radial), LTU (Left Thumb Ulnar), LIU (Left Index Ulnar), LMU (Left Middle Ulnar), LRR (Left Ring Radial), LRU (Left Ring Ulnar) and LLR (Left Little Radial) areas. The assessment of sexual dimorphism from fingerprint ridge density may allow the investigating officer to narrow down the forensic investigation based on either sex.