Abstract: This study provides a mathematical link between fingerprint pattern types, the ethnicity in which they occur, and the fingers on which they occur. In doing so, the study reveals an order based on priority of occurrence of the most likely fingerprint pattern types to occur in a specific ethnicity along with the most likely fingerprint pattern types to occur on a specific finger. This study uses statistical analysis to validate the prioritized order of occurrence.

Introduction

As one of the many fields of forensic science that can benefit from additional research, fingerprint identification is probably the most prominent. Within recent years, many latent print examiners have been questioned in both professional and social situations as to whether fingerprint evidence should be considered scientific. This questioning caused latent print examiners to realize the pressing need for various types of ongoing research on the subject of fingerprints.

Fingerprint patterns are formed on the fetus in the womb. Wertheim and Maceo reported that various cellular attachments ensure the permanence of friction ridges, while cellular stresses and cellular distributions account for the individuality on all “three levels” of detail [1]. They also state that fingerprint ridge counts and fingerprint pattern types are predominantly affected by two combined timing events: the onset of epidermal cellular proliferation and the timing of the regression of the volar pads. The total friction ridge count, according to Holt, as reiterated by Wertheim and Maceo, is the most inheritable feature in dermatoglyphics and is also determined by the symmetry of the volar pad at the time of ridge proliferation [1]. This, therefore, suggests that the combined timing event of the onset of ridge proliferation along with the regression of the volar pad is also an inheritable trait. Consequently, the type of fingerprint pattern that occurs on the fetus is dependent upon the combined timing events of the onset of ridge proliferation and the volar pad regression. This idea that ridge formation, alignment, and overall pattern shape are affected by the time of the volar pad’s appearance along with its regression was asserted by Cummins as early as 1929 [2] and was still supported by Ashbaugh over sixty years later in 1991 [3]. Ashbaugh also concurs with Hale’s earlier research in 1952 where he aphoristically states that heredity dictates that volar skin will form friction ridges, also that the friction ridge pattern will follow a genetic master plan which involves volar pads [4]. The formula is carried in our genes [3].

The latter is supported by numerous studies of the ridge patterns of monozygotic twins whereas it can be concluded that heredity may play a significant role in the overall ridge configuration and pattern (level 1 detail), but Wertheim and Maceo, Hale, Ashbaugh, and others all concur that it does not determine the outcome of the individual ridge growth (level 2 and 3 detail) [3], because the ridge alignment, shape, and minutiae location all evolve randomly through various stresses and cellular distributions, thus reaffirming the individuality of fingerprints on both level 2 and 3 detail [1]. Additionally, in their initial formation, most volar pads usually tend to swell up symmetrically and, as they regress, some tend to regress faster on one side than the other, which will account for an asymmetrical volar pad during the middle stages of volar pad regression [1]. With that in mind, if a fetus has an early timing of the onset of ridge proliferation before the volar pad has regressed much, then the volar pad will most likely be symmetrical at the time of proliferation, resulting in a whorl fingerprint pattern. On the other hand, if a fetus has a late timing of the onset of ridge proliferation after the regression of the volar pad, then the volar pad would have already merged with the contours of the finger, resulting in an arch fingerprint pattern. A loop fingerprint pattern will develop if the timing of the onset of ridge proliferation occurs while the volar pad is asymmetrical. Therefore, if a fetus has the onset of ridge proliferation during the middle stages of volar pad regression while the volar pad is most likely asymmetrical, then a loop fingerprint pattern will occur. All other subcategories of fingerprint patterns develop at different combined timing events of the onset of ridge proliferation and volar pad regression [1]. The latter information, along with the inheritability of the combined timing event of the onset of ridge proliferation, along with volar pad regression, suggests the possibility of fingerprint pattern types to be an inheritable feature.

Methods

A study of this hypothesis was performed in an attempt to validate the results of the author’s pilot study using nearly 400 fingerprint records, totaling nearly 4,000 fingerprints, and to determine whether certain fingerprint patterns dominate the different ethnicities. This current study consisted of examining 2,000 fingerprint records, totaling 20,000 fingerprints, from the Athens/Clarke County Police Department in Georgia. The sample consisted of 5,000 fingerprints from each of the four major ethnicities: White, Black, Asian, and Hispanic. Each of the 20,000 fingerprints was examined, and the ethnicities in which they occurred, along with the fingers on which they occurred, were recorded. The data were then set up into different tables comparing the different variables. The tables compared fingerprint patterns and ethnicity, fingerprint patterns and the two hands on which they occur, and fingerprint patterns and the fingers on which they occur. Basic mathematical analysis, such as percentages and frequencies, was performed on the data. Along with the basic mathematical analysis, statistical analysis needed to be done on the data. The Chi-Square: Test for Independence was selected because of its ability to quickly test the level of dependency that many variables had on each other in a set of data. Furthermore, the chi-square test is a statistical analysis test that determines whether the relationship of the variables being compared is significant, or in other words, whether the variables are dependent upon each other. It does this by examining the difference in the quantity of the variables observed compared to the quantity of the variables expected assuming there was no bias expressed in the distribution of fingerprint patterns so that they were distributed equally among both the four ethnicities and the five fingers. It is important to keep in mind that the ethnicities of the individuals used in this study were drawn from contemporary arrest records. The anthropological designations of the individuals used in both studies were superficially given by the arresting law enforcement officer. With the fact that the ethnical assignments were given by anthropologically untrained officials, coupled with the lifestyle of contemporary times with interracial couples, it would be a grave mistake to totally attribute one person’s specific ethnic makeup to be exact to that of a whole larger population. The four different ethnicities used in this study were based on broad classifications of the individuals’ ethnic makeup. The Asian ethnicity, for example, includes individuals whose dominant ethnicity is Asian whether it is Chinese, Japanese, Vietnamese, and so forth. Put frankly, it is important to remember that the ethnicity of the individuals used in the study was assigned through human intuition and is consequently prone to human error, along with the fact that there are no “pure” ethnicities in the world today. However, dominant ethnicities in these mixed race individuals still exist and are prevalent today. Because of this, the resulting list designates the most likely ethnicity to its corresponding fingerprint pattern.

Ethnicity Results

When the mathematical analysis was performed on the data, the basic analyses of percentages and frequencies foreshadowed the very high statistically significant levels revealed for the relationship of fingerprint patterns and ethnicity. In-depth analysis of the results of the chi-square test (P<.001) revealed an order based on priority of occurrence of fingerprint patterns in the most likely ethnicity in which they occur. Even though the results show that every fingerprint pattern occurred in every race, some fingerprint patterns noticeably dominated some races more than others did. Statistically speaking, the lower P-value, or alpha level, results in the higher the significance level of the relationship of the variables being compared, the alpha level of .05 being the fine line of significance. If the overall chi-square value for the table is larger than the critical value at the appropriate degrees of freedom and .05 alpha level, then it can be concluded that the relationship of the variables is significant, or in other words, the variables are dependent upon each other. In the analysis pertaining to the relationship of fingerprint patterns and ethnicity, the chi-square value was much larger than the critical value at the .001 alpha level and the appropriate degrees of freedom, indicating a high rate of dependence between the two variables. Based on the statistical analysis, a prioritized list (Table 1) was created that shows the relationship of fingerprint patterns and the most likely ethnicity in which they occur.

Table 1
Prioritized list 1. Fingerprint traits and ethnicity.

Pattern to Finger Occurrence Results

The mathematical analysis was also performed on the data involving fingerprint patterns and the hands on which they occur. Again, the basic analysis of percentages and frequencies foreshadowed the results of the chi-square analysis corresponding fingerprint patterns and the hands on which they occur. With statistical analysis, the relationship of the variables of fingerprint patterns and the hands on which they occur failed to be significant. Therefore, the variables of fingerprint patterns and the hands on which they occur are not dependent upon each other. In fact, along with most other bodily features involving bilateral symmetry, there were a relatively equal number of the same fingerprint patterns occurring on the two hands, sometimes even down to the same fingers between the two hands. Once it was established that the relationship of fingerprint patterns and the hands on which they occur was not significant and was not dependent upon each other, the data were organized into another table corresponding fingerprint patterns and the fingers on which they occur in total disregard to which hand they occurred on. Based on the results of the statistical analysis using the chi-square test, it can be concluded that fingerprint patterns are dependent upon the finger on which they occur. Again, the results of in-depth statistical analysis (P<. 001) revealed an order based on priority of occurrence of fingerprint patterns on the most likely fingers on which they occur. Keep in mind, again, that even though the results show every fingerprint pattern occurred on every finger, some fingerprint patterns noticeably dominated specific fingers more than others did. Statistically speaking, with the relationship of fingerprint patterns and the fingers on which they occur, the chi-square value was much larger than the critical value at the .001 alpha level and the appropriate degrees of freedom again, resulting in a high rate of dependence between the two variables. Based on the statistical analysis, another prioritized list (Table 2) was created that shows the relationship of fingerprint patterns and the most likely fingers on which they occur. The prioritized list, which is based on statistical and scientific analysis, may also be used as a means to predict the fingers on which the fingerprints occur using the established fingerprint patterns in order to expedite the comparison of latent prints to known tenprints by narrowing the search parameters as to the most likely finger before even referring to the tenprint for comparison.

Summary and Discussion

The results of the prioritized lists that were developed support the purpose of the validation study stating that fingerprint patterns are indirectly inherited by the inherited timing sequences of the onset of ridge proliferation coupled with the regression of the volar pads. Going back to the prioritized list corresponding fingerprint patterns to the most likely ethnicity in which they occur, for example, whorls tended to dominate the Asian race more than any other race. Therefore, it can be surmised that because whorls are formed on symmetrical volar pads, Asian fetuses may tend to undergo the onset of ridge proliferation earlier or before much of the regression of the volar pads, resulting in the occurrence of more whorls than most other fingerprint patterns. Likewise, the black race tended to be dominated by loops and arches. Therefore, it can possibly be inferred that because loops and arches are formed during the middle to late stages of volar pad regression while the volar pad is asymmetrical or after it has already merged with the contours of the fingers, black fetuses may tend to undergo a much later timing of the onset of ridge proliferation during the middle to later stages of volar pad regression. However, these predictions are based on assumptions brought about in the study and therefore need further investigation to conclude the exact reasons as to why certain ethnicities are dominated by certain fingerprint pattern types.

Table 2
Prioritized list 2. Fingerprint traits and fingers.

As for the prioritized list corresponding fingerprint patterns to the most likely finger on which they occur, the immediate application is during AFIS and IAFIS searches. For IAFIS searches, especially where the search parameters must be limited to roughly 30% of the database, knowing the most likely finger from which the latent print originated enables the examiner to open the search parameters in other areas of his or her search, thereby reducing the number of different searches required for each subject. The overall results of this study support both the intuition of veteran latent print examiners and past dermatoglyphical studies involving the linkage of fingerprint pattern types, the ethnicity in which they occur, and the fingers on which they occur.

Conclusion

Besides the complex biological structure and development of fingerprints and the fact that they have upheld their reliability for the last century and have been generally accepted as a means of identification, skeptics continue to legally challenge the admissibility of fingerprint identifications. Therefore, with studies similar to this one using scientific analysis, the recent rise of skeptics may begin to fall as evidence supporting the accuracy and reliability of fingerprint examinations is developed. Although this validation study was not done on an extremely large sample of individuals, the size was statistically large enough for the results to begin to be accepted into the general population. The very high significance levels revealed in the study warrant further research and studies. Additional validation studies are needed to more fully verify the theories developed by different latent print examiners around the world and to uphold a century of scientific excellence in the field of fingerprint examinations.

Acknowledgments

I would like to extend a special thanks to a few of the crucial people who helped make this study possible: Shannon Hale, for her professional assistance; Dr. Ed Baily, for his statistical guidance and verification of calculations; Sgt. David Leedahl and Chief Joseph Lumpkin of the Athens-Clarke County Police Department, for their assistance in the materials used in this study; and of course, Dr. Ron Swofford and Dr. Joyce Swofford, for their continued encouragement and upport.

For supporting statistical data or further information, please contact:

Henry J. Swofford
(404) 277-8724
hswofford@hotmail.com

References

1. Wertheim, K.; Maceo, A. The Critical Stage of Friction Ridge and Pattern Formation. J. For. Ident. 2002, 52 (1), 35-85.
   
   
2. Cummins, H. The Topographic History of the Volar Pads (walking pads, Tastballen) in the Human Embryo. Contributions to Embryology; No. 394; Carnegie Institution of Washington: Washington, DC, 1929, pp 103-126.
   
   
3. Ashbaugh, D. R. Ridgeology. J. For. Ident. 1991, 41 (1), 16-64.
   
   
4. Hale, A. R. Morphogenesis of Volar Skin in the Human Fetus. Am. J. of Anat. 1952, 91 (1), 147-173.