Human beings are highly developed mammals in the animal kingdom. As each human being differs from another, so do the fingerprints (Quetelets law).1 No two fingerprints match even in homozygous twins.
Sir William Herschel used fingerprints for the identification of an individual in India in 1858 to prevent impersonation.2 Sir Francis Galton systematized it to identify criminals, which was officially adopted in England in 1894 and was modified further by Sir Edward Henry 2, hence called the Galton system or Henry-Galton system.
Like similarities, there are many dissimilarities in fingerprints due to racial, familial and sexual differences. Studies were conducted to study sexual dimorphism in fingerprints.5, 6 In Forensic practice, the whole palm or sometimes the whole finger may not be available; in such cases, sex determination may help Investigating officer in solving the case. Given this, studies were done on Sex determination by counting the number of ridges in palm,7, 8 and fingers both in India and abroad.9
This inspired us to take up this study on fingerprint ridge density and its sexual dimorphism.
Materials and Methods
The materials used for this were.
Inkpad (Black/Blue color)
Printed pro forma
A magnifying glass with the light source
Subjects were chosen from medical students studying in Narayana Medical College, Nellore Andhra Pradesh. 120 Medical students (60 girls + 60 boys) participated in the study. The procedure and the purpose of the examination were explained to them, and consent was obtained.
Collection of the prints
The subjects were asked to wash their hands with soap and water before taking the prints. Inkpad is used for smudging their fingers with ink. Then the smudged fingers were applied carefully in the respective spaces in the pro forma. Only plain prints were obtained. No roll prints were taken.
After taking the Plain fingerprints of all the ten digits of 120 Medical students (60 girls + 60 boys), the total number ridges per 0.25sq.cm from each finger were counted by using a graph paper with a hole made of 0.25 sq. cm. (0.5 X 0.5 cms.) from the prominent central area. The magnifying glass was used while counting to get a better look. The counting was done, and all precautions were taken to avoid Inter and Intraobserver variations.
The results thus obtained were fed into the computer, and the statistical data is analyzed.
Statistical Analysis and Results
The data has been entered into MS-Excel, and statistical analysis has been done using IBM SPSS Version 25.0. For categorical variables, the data values are represented as numbers and percentages., the chi-square test is used to test the association between them. For continuous variables, the data values are shown as mean and standard deviation. The student’s t-test is used to test the mean difference between the two groups. All the P-values having less than 0.05 are considered statistically significant. (Table 1, Table 2)
In females, the mean ridge density for ten fingers is 148. 67 and (Range 145 -153) for five fingers of left hand is 73.38 (range 71-75) and 75.28 (Range 72-78) for right hand. The ridge density for each finger is 14.86/ 0.25 sq cms.
There is no statistically significant difference in fingerprint ridge density of left and right hands in males, but in females, the ridge density in the right hand is slightly more than the left. (75.28:73.38).
Many studies were conducted on fingerprint ridge density to determine sexual dimorphism in India as well as abroad.
Sudesh Gungadin9 conducted a study on 500 subjects (250 male and 250) female in Karnataka. According to this study, the females showed an increased fingerprint ridge density than males. The mean values of females to males were 146 and 128, respectively. Similar results were observed in our study.
In the study conducted in South India involving 100 males and 100 females by Kumar S, Jirli, Prasanna, Honnungar, Ravindra, Babu, Raghavendra, Kumar, M.S10 the females have a ridge density of 16/25 mm2 and males 15 /25 mm2.
In the study conducted by Amit Patil, Amrit Malik, Trezashirole.11 On 170 subjects from Dr. DY Patil Medical College Mumbai. The ridge density in males is between 8-12.90 / 25 mm 2 and 10.2 -15/ 25mm2 in females.
Arun Kumar Agnihotri, Vandna Jowaheer, Anishta Allock12 in their study involving 200 medical students, 100 men and 100 women, opined that women tend to have a higher ridge density in comparison with men.
Dhall L K and Kapoor B13 conducted a study in 245 males and 246 females belonging to the Punjabis of Delhi region concluded that females have significantly higher ridge density than males in all five areas of finger upper radial, radial, ulnar, upper ulnar, and proximal.
Similar studies were conducted in other countries also. Wahdan, Amira & Khalifa, Heba14 and summarized that the females showed significantly greater ridge density >1187/25mm2 at a cut of value in their study involving 200 volunteers, 100 male, and 100 female Egyptian population.
In the study conducted on Northeastern Thai teenagers by Pattanawit Soanboon Somsong Nanakorn, Wibhu Kutanan15 among 353 volunteers, 191 male and 162 females of age groups between 14 – 18 and 18 – 24 years, significant differences between genders and age groups were obtained. Females exhibited higher ridge density and narrow ridges than males, and a decrease in ridge density with age was also noticed.
However, Maninder Kaur16 found out that male prisoners showed more fingerprint ridge density than female prisoners in the study involving 125 Prisoners, 77 male and 48 Female prisoners of Haryana. This study is contrary to the present study and many similar other studies—the reasons for the same need to be evaluated.
The fingerprint ridge density among the females is higher than the males. The females showed a range of 145 to 153 ridges /0.25 sq. cms compared to males, the range being 124 to 134 ridges / 0.25 sq cms. The mean value of female to male is 14.8 with an SD of 234, and that of the male is 12.85 with an SD of 2.86.
There is no statistically significant fingerprint ridge density of left and right hands in males, but in females, the ridge density in the right hand is slightly higher, requiring further evaluation.
Limitations and Recommendations
The study was conducted involving Medical students of only one college of Andhra Pradesh, and the sample size is small (one hundred and twenty only). A large sample size involving more subjects across India will give more accurate results.