Classification of patterns
The study was conducted to suggest and formulate an alternative approach to classify the lip prints. The pattern of wrinkles and grooves present in the lip impressions was analysed precisely by dividing the lip impression into ten areas or quadrants. Patterns present in 500 lip print samples and their subsequent 5000 quadrants were analysed thoroughly to determine various pattern types which existed either singly or as a blend of different types of patterns. After analysis, seven types of Basic Patterns of wrinkles and grooves were found to be present in the lip impressions of the males as well as females, described as follows:
Lines: The wrinkles and grooves running unidirectional across the lip prints forming a pattern, but lacking any curvature and not splitting further, were named as Lines (Table 2).
Curves: The wrinkles and grooves running unidirectional across the lip prints, having a curvature, but not splitting further were named as Curves (Table 2).
Bifurcations: The wrinkles and grooves running unidirectional across the lip prints, lacking any curvature, and splitting further into two divisions (inclined in the opposite directions to each other) were named as Bifurcations (Table 2).
Curved Bifurcations: The wrinkles and grooves running unidirectional across the lip prints at an angle of curvature and splitting further into two divisions (inclined in the opposite directions to each other) were named as Curved Bifurcations (Table 2).
Intersected Bifurcations: The wrinkles and grooves running unidirectional or bidirectional across the lip prints, lacking any curvature, splitting further into two divisions (inclined in the opposite directions to each other) and merging into each other, were named as Intersected Bifurcations (Table 2).
Curved Intersected Bifurcations: The wrinkles and grooves running unidirectional or bidirectional across the lip prints at an angle of curvature and splitting further into two divisions (inclined in the opposite directions to each other) as well as merging into each other were named as Curved Intersected Bifurcations (Table 2).
Squares: The wrinkles and grooves running bidirectional across the lip prints, crossing each other at a right angle without any curvature, and not splitting any further were named as Squares (Table 2).
These aforesaid Basic Patterns were further divided into various subtypes based on the direction and angularity of the lines forming the patterns (Table 2). Various types of Basic Patterns and their respective subtypes, along with their macro photographs, have been given in Table 2. Out of the seven Basic Patterns (as shown in Table 2), six patterns (viz. Lines, Curves, Bifurcations, Curved Bifurcations, Intersected Bifurcations, and Curved Intersected Bifurcations) ought to be divided into three subtypes (Vertical, Horizontal, and Oblique), which in turn gave rise to 18 varieties of Basic Patterns (Table 2). All the subtypes of Basic Patterns of lip prints could be further differentiated into diverse sub-sub types like left, right, upward, and downward depending upon the inclination and orientation of wrinkles or lines which form the lip print patterns. However, the Squares could not be divided into any subtypes.
Similarly, various types of Combination Patterns and their respective subtypes, along with their macro photographs, have been given in Table 3. It is evident from Table 3 that two or more types or subtypes of Basic Patterns could be present together in a lip print area to give rise to another pattern as a whole, which makes a Combination Pattern. Accordingly, 43 different types of Combination Patterns have been assorted. These patterns could be further differentiated into various forms or subtypes, depending upon the subtypes of Basic Patterns constituting the Combination Pattern. Statistically, the amalgamation of 7 varieties of Basic patterns gave rise to 43 different appearances of Combination Patterns.
The patterns that could not be classified and categorized as either Basic or Combination patterns were designated as Miscellaneous patterns.
Validation of distribution of basic and combination patterns
In order to validate the distribution of Basic and Combination Patterns, 500 lip print samples were statistically analysed to calculate the frequency, and the corresponding values have been given in Tables 4 and 5. As in the present study, the whole lip print was divided into 10 parts or quadrants, all the quadrants (5000) were also analysed thoroughly to study the frequency of Basic and Combination Patterns in each quadrant. Similarly, the percentage frequency of these patterns was statistically calculated, which is numerically summarized in Tables 4 and 5.
Table 4 and Fig. 2 show the frequency of Basic Patterns in lip print samples (whole lip) and their subsequent quadrants. It is evident from Table 4 (Fig. 2) that Lines (Basic Pattern) were found to be present in 3.60% samples and 0.38% quadrants. Curves and Bifurcations repeated themselves (frequency) in 1.00% and 37.00% samples; and in 0.10% and 6.12% quadrants, respectively. Similarly, Curved Bifurcations, Intersected Bifurcations, and Curved Intersected Bifurcations were found to be distributed (frequency) in 38.00% samples; 7.92% quadrants, 54.60% samples; 11.46% quadrants and 63.60% samples; 14.64% quadrants, respectively. Also, the Squares were present in 4.20% samples and 0.50% quadrants.
Similarly, Table 5 and Fig. 3 represent the frequency of Combination Patterns (43) in the whole lip print samples and their subsequent quadrants. It is evident from Table 5 (Fig. 3) that among Lines (major pattern) and their combinations with other Basic Patterns (6), the pattern Lines + Bifurcations was found to have the maximum frequency, i.e. 9.40% (sample-wise) and 1.02% (quadrant-wise), followed by Lines + Squares (present in 7.00% samples and 0.72% quadrants). Simultaneously, the pattern Lines + Curves was found to have the minimum frequency of distribution (0.60% in samples and 0.06% in quadrants).
Among various Combination Patterns of Curves (6), the pattern Curves + Curved Bifurcations was found to possess maximum frequency, viz. in 1.00% samples and 0.12% quadrants; while Curves + Lines were found to have minimum distribution (in 0.40% samples and 0.04% quadrants). Maximum sample-wise, as well as quadrant-wise distribution frequencies of various Combination Patterns of Bifurcations (major pattern), was found to be 31% (sample-wise) for Bifurcations + Squares and 4.62% (quadrant-wise) for Bifurcations + Curved Bifurcations, respectively. Similarly, minimum distribution frequencies of various Combination Patterns of Bifurcations were held by Bifurcations + Curves, i.e. 1.20% (sample-wise) and 0.12% (quadrant-wise), respectively.
Among the Combination Patterns embodying Curved Bifurcations as the major pattern (6), Curved Bifurcations + Squares were found to be distributed in 36.20% samples and 5.58% quadrants (maximum frequency); while Curved Bifurcations + Curves were found to be minimally distributed in 2.00% samples and 0.20% quadrants, respectively. Similarly, considering the patterns presenting Intersected Bifurcations as the major pattern (6), Intersected Bifurcations + Squares were found to possess the maximum distribution frequency, viz. 33.00% (sample-wise) and 5.54% (quadrant-wise), while Intersected Bifurcations + Curves showed minimum distribution, i.e. in 1.20% samples and 0.12% quadrants. The maximum, as well as minimum sample-wise and quadrant-wise distribution frequencies of various Combination Patterns of Curved Intersected Bifurcations (6), were observed in Curved Intersected Bifurcations + Squares (in 25.80% samples and 3.84% quadrants) and Curved Intersected Bifurcations + Curves (in 0.60% samples and 0.06% quadrants). In the case of Squares as the major pattern (6), the combination Squares + Bifurcations was extremely distributed in 28.00% samples and 3.98% quadrants. Also, Squares + Curves were scarcely present in 0.80% samples and 0.08% quadrants. Meanwhile, the Miscellaneous Pattern was fairly distributed in 33.60% samples and 4.94% quadrants.
Gender-based frequency of basic and combination patterns
The gender-based frequency estimation of various Basic patterns revealed that some lip print patterns were predominantly present in the female subjects, while others were more frequently present in the males. It is evident from Tables 6 and 7 that the ‘CIB’ Basic pattern was predominant in female samples. On the contrary, the ‘B’ and ‘CIB’ patterns were equally dominant in the male samples. The ‘L’ and ‘C’ patterns were least present in the female samples. Likewise, the ‘S’ pattern was least dominant in the male lip print samples. Also, the ‘C’ basic lip print pattern was not observed in any of the present study’s male subjects.
The frequency analysis of various Combination patterns of female and male lip print samples (Tables 8 and 9) revealed that the ‘Miscellaneous Pattern (MP—57%; 8.9%)’ predominates in female lip prints followed by the patterns ‘IB + CB’ and ‘S + B’. However, the ‘B + CB’ pattern was predominantly found (65%; 11.8%) in the male lip prints followed by CB + B’ and ‘MP’ patterns. The least common Combination patterns found in the female samples were ‘L + C’, ‘L + CIB’, ‘C + L’, ‘C + B’, ‘C + IB’, ‘C + CIB’, ‘C + S’, ‘CB + C’, ‘IB + C’, ‘CIB + C’, and ‘S + C’ with only 1% chances of occurrence in a group of 100 samples. On the contrary, the least commonly occurring Combination patterns in the male samples were ‘C + L’, ‘B + C’, ‘S + L’, and ‘S + C’ with % frequency (each). Likewise, the patterns ‘L + C’, ‘L + IB’, ‘C + B’, ‘C + IB’, ‘C + CIB’, IB + L’, and ‘CIB + C’ were not observed in any of the male lip print samples analysed in the present study.
From the chi-square test of independence for Basic patterns, χ2 came out to be 20.31991. This calculated value of χ2 was greater than the critical value (9.49) at α = 0.05 and Df = 4 [Degree of freedom = (r − 1) (c − 1)]. Hence, the null hypothesis was rejected. It showed that the Basic pattern is dependent on the sex of the sample contributor. Similarly, for the Combination patterns, the χ2 came out to be 269.0968. This calculated value was greater than the critical value (40.113) at α = 0.05 and Df = 26 [Degree of freedom = (r − 1) (c − 1)]. Thus, the null hypothesis was rejected in the case of Combination patterns. Therefore, the statistical analysis of the data collected for both types of patterns inferred that the frequency of patterns (Basic and Combination) depends upon the sex of the lip print samples.
Blind trials
Noteworthy observations came out of the blind trials. The hard copies of original lip print samples were analysed separately and classified according to the Suzuki and Tsuchihashi system of lip print classification. According to this system, each whole print was divided into 4 quadrants and classified as Type I or Type I′ and so forth, given by Suzuki and Tsuchihashi system. The same lip print samples were independently analysed according to the proposed (new) classification system, where a whole print was divided into 10 quadrants. All the whole prints were successfully classified. It was later attempted to classify some partial lip print (1/10th size of the whole print) samples and link them to their source of origin using the Suzuki and Tsuchihashi’s system and the novel system of the present study as well. Some of the partial impressions (quadrants) of the Test samples could not be assigned any of the Suzuki and Tsuchihashi system’s values or codes, like the patterns possessing horizontally aligned angular bifurcations or intersected bifurcations having curvature. The patterns which were not addressed by Suzuki and Tsuchihashi system were classified according to the present novel alternate classification system, and the partial lip prints (quadrants) were successfully linked to their source of origin.