Introduction

Palm prints found at the crime scene or severed hands collected from incidences such as natural disasters and accidents can assist in identifying the individuals. Handprints, including fingerprints and palm prints, are crucial and commonly encountered pieces of physical evidence in various crimes. The location of these prints on objects at the crime scene may vary. Palm prints can be significant for personal identification when fingerprints are unavailable or smudged.

Stature estimation can help correlate witness statements and verify or disprove alibis. However, variations in hand dimensions according to sex and population groups have been observed in Australian, Egyptian, Indian, and Bangladeshi populations (1–15)

Three types of palm prints can be collected from any crime scene: latent palm prints (found on surfaces like glass, steel, or paper), patent prints (such as bloody or colour prints), and plastic palm prints (impressions left in materials like wax, mud, or clay). These can be crucial in cases where fingerprints are smudged, blood-stained, or missing, and where stature assessment or personal identification is necessary (16). Considering anthropological criteria such as stature and body dimensions, the process of narrowing down the pool of suspects or victims can be significantly improved using palm prints (17–19). Standards and databases for estimating and identifying stature and sex from palm prints have been established for several populations (20).

Similar to flat feet, arches can also be seen in the palm. Extensive research has been conducted on using palm and palm print dimensions to estimate stature and sex. Palm prints can be recovered using a scanner or a charged coupled device, or they can be taken using ink and paper. However, no study has been conducted to determine gender from the arch dimensions and central curve of palm prints.

A typical palm consists of principal lines, namely the heart line, life-line and head-line (Figure 1). It also includes regions such as the interdigital, thenar and hypothenar areas, as well as datum points. The geometric features of a palm include its width, length and area, along with wrinkle features and delta point features.

The present study aims to determine gender based on the central curvature and arch observed in palm prints. These dimensions can be useful in forensic investigations where other evidence for gender determination is unavailable.

Methods

Sample collection

For this study, palm prints were collected from 200 individuals (100 males and 100 females) from Haryana, India, ranging in age from 18 to 45 years. To avoid errors, only right-handed participants were included. All participants provided written consent to volunteer for the study. Palm prints from both the left and right hands were taken using ink, a roller, and a glass slab on A4 white sheet.

Anthropometric measurements and techniques

All measurements were taken in a well-lit room using a consistent setup. The ink and roller technique was employed on a glass slab, and measurements were recorded in centimetres using a scale. Individuals with any diseases or deformities of the fingers or hands were excluded from the study. Four standard reference points were established for the parameters: the centre point between the middle and ring fingers was designated as UOC (Upper of Centre), the middle point of the palm crease as DOC (Down of Centre), the starting point of the heart line as HOC (Heart-line of Circle), and the point where the heart line and headline begin as LOC (Life-line of Circle) (Figure 2). Anthropometric measurements from UOC, DOC, LOC, and HOC of both the right and left palms were taken.

Figure 1: Handprint of male showing regions, lines and datum points.

Figure 2: Right handprint of female showing UOC, DOC, LOC and HOC with hand crease and centre point.

Statistical analysis

The data were analysed using IBM SPSS version 26. Gender-based differentiation between male and female palm prints was examined using the Chi-Square test. which is typically used to compare two sets of data. The test estimates the likelihood of the observed differences, assuming the null hypothesis is true. Both the null and alternate hypotheses were applied to the samples to determine whether there is a significant correlation between palm arch and gender:

Null hypothesis (H⁰): There is no significant difference between the middle area of palm print having arch or flat arch (having no arch or low arch) of male and female palm prints.

Alternate hypothesis (H¹): The alternative hypothesis proposes that there is a significant difference between the male and female palm prints based on arch.

The Chi-Square test was performed at a 95% confidence level and 0.05 significance level at the respective degree of freedom.

Results

To conduct the descriptive statistics, all parameters (UOC, DOC, LOC, and HOC) were analyzed for both males and females. On the right hand, it is noticeable that all parameters for females possess higher values than males (Table 1). The mean values for the right-hand parameters in females are higher than those in males. Similarly, the left-hand parameters in females show a higher mean difference compared to males. Overall, females exhibit significantly higher values than males in both hands.

Upper of Circle (UOC)

A visible difference in the dimensions of palm prints is observed when comparing male and female palm prints. In 75% of left-hand cases, the measurement of the arch is less than 1cm for males, and in 97% of right-hand cases, it is less than 1 cm at the upper of center region (UOC). Conversely, 92% of female subjects have an arch above 1 cm in the left hand, and 77% in the right hand (Table 2).

Table 2 represents the count of UOC values for males and females, above and below 1cm, for both hands. The Pearson Chi-Square test values indicate significant differences between the sets. The left palm print’s Chi-Square value is 92.4 with 1 degree of freedom, and the right palm print’s value is 114.08, both significantly higher than the critical value of 3.841. This signifies that the null hypothesis is rejected, and the alternative hypothesis, which states that there is a significant difference, is accepted. Additionally, there is a notable difference between the right and left hands for both genders, with the right hand’s Chi-Square value being higher.

Down of Circle (DOC)

A noticeable difference is observed in the DOC region between male and female palm prints. Male participants have arch length less than 1 cm in 67% of left-hand cases and 91% of right-hand cases. In contrast, female participants have an arch greater than 1 cm in 100% of left-hand cases and 99% of right-hand cases (Table 3).

The Pearson Chi-Square value for the left palm print is 99.38 with 1 degree of freedom, and for the right palm print, it is 163.04, both significantly higher than 3.841. This indicates that the null hypothesis is rejected, and the alternative hypothesis of a significant difference between male and female palm prints is accepted. The right hand's difference is more prominent than the left hand's for both genders.

Lifeline of Circle (LOC)

There is a visible difference in the dimensions of palm prints between males and females in the LOC region. The arch is less than 1 cm in 91% of left-hand cases and 92% of right-hand cases for males. For females, the arch is above 1 cm in 79% of left-hand cases and 100% of right-hand cases (Table 4). The Chi-Square values for the left palm print is 99.43 and for the right palm print is 170.3, both significantly higher than the critical value. The right-hand values for males and females are higher than the left-hand values, indicating a significant difference between the hands for both genders

Headline of Circle (HOC)

A noticeable difference is observed in the HOC region when comparing male and female palm prints. In females, the arch is more than 1 cm in 100% of both left and right-hand cases. In males, the arch is less than 1 cm in 65% of left-hand cases and 79% of right-hand cases (Table 5). The Chi-Square value for the right palm print is 130.5, and for the left palm print, it is 89.0, indicating a significant difference between male and female palm prints.

Discussion

These findings suggest that the observed differences in palm dimensions between males and females could be attributed to various factors such as physical or muscular ability, or skin softness and tenderness. The study’s results have significant implications for forensic science, particularly in criminal investigations for determining sex. The statistically measurable differences in the arch characteristics of palm prints provide a reliable method for gender identification, which has not been extensively utilized in individual identification processes.

Palm arching characteristics in prints, both latent and patent, as well as an individual's physical effort in physical activities, may be used to determine gender. These parameters can be applied for personal identification, gender determination, and assessing physical activity in investigations.

The terminology "arch, low arch, and no arch" along with the arch area can be statistically measured and predicted for males and females, offering a new avenue for forensic analysis. This research highlights the importance of considering gender differences in palm print analysis and dey(21–23)opens up the potential for further studies to explore additional biometric characteristics that can aid in individual identification.

Previous studies have suggested that there are significant sexual dimorphisms in the anthropometric measurements of the hand, which can be utilized for personal identification purposes. Digit ratios, especially those involving the second and fourth digits, have been found to exhibit distinct differences between males and females. Factors like prenatal sex hormone levels and differential placing of flexion creases have been proposed as potential contributors to these sex differences in digit ratios. (22–24)

The present research aims to investigate the statistical differences in arch characteristics of palm prints between males and females and explores the reliability of using these features for gender identification in forensic applications.

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