8 Dermatoglyphics

Dr. Priyanka Khurana

Contents:

1. Introduction

2. Types of Dermatoglyphic prints

3. Morphogenesis of Friction ridges

4. Fundamental principles of fingerprints

5. Fingerprints:

5a. Morphology of fingerprint

5b. Comparison of a Single Fingerprint

5c. Fingerprint Classification

5d. Henry’s Classification System

6. Palm Print

6a. Morphology of Palm prints

7. Sole Prints

7a. Morphology of Sole prints

8. Summary

Learning Objectives:

•  To identify fingerprints;
•  To classify and compare fingerprints;
•  To classify palm prints and
•  To identify and classify sole prints.

1. Introduction

The largest organ of the human body is skin which covers the body’s outer surface and performs the function such as protection of internal organs and receiving of external stimuli. The texture of skin on the entire human body is neither same nor smooth. The skin especially on inner side of hands (palm and fingers) and feet (sole and toes) are raised in the form of structure of rows separated by furrows or depressions. These elevated portions of the skin are called as friction ridges or dermal ridges. The main function of these friction ridges is to impart gripping.

Every friction ridge contains sweat pores. The perspiration discharged from these sweat glands along with dead skin cells, proteins, fats, and material creates impression of the ridges on the surface of contact. Thus, the surface from which finger prints are obtained displays an accurate representation of the print. The impression from the friction ridges of fingers of hand and feet are collectively called as fingerprints whereas those obtained from volar surface i.e palm of hand and sole of feet are referred as palm prints, and soleprints respectively. The scientific study of prints or impressions formed by palms, fingers, soles and toes is called Dermatoglyphics. The term Dermatogyphics is derived from Greek words Derma meaning Skin and Glyph meaning carving. The science of comparison of friction ridge is called as Dactyloscopy.

2. Type of dermatoglyphic prints

•  Visible prints: Those prints which are visible through naked eyes are called as visible prints. For example blood print, mud print, dust print, inked print.
•  Plastic print: The prints formed on the materials that forms molds after coming in contact surfaces such as wax, butter, ghee, semi dry paint or putty, cement are termed as plastic prints. All plastic paints are visible paints.
•  Latent prints: Those prints which are not visible through naked eyes are designated as Latent. These prints are developed with the help of some chemicals.

3. Morphogenesis of Friction ridges

The friction ridge first appears between 12th and 16th week of gestational age of embryo and estimated to be complete by 24th week. The major development of friction ridges occur between 11 and 20 weeks of estimated gestational age.

4. Fundamental principles of fingerprints: Though the general term fingerprint is used but all principles mentioned below applies to palm and sole prints as well.

•  Fingerprint is an individual characteristic. The statement implies that no two individuals or fingers of the same person can have the same fingerprint. Identical twins may have are similar fingerprints but not their fingerprints are not absolutely identical.

The individuality of a print is imparted not by its shape or pattern but by its specific ridge features which are called as minutiaes. The types and locations of specific minutiae impart the uniqueness to the fingerprint and this uniqueness is the basis for fingerprint comparison. In other word two individual may have similar fingerprint pattern but due to difference in the type, number and position of minutiaes the two fingerprints can be differentiated.

•  Fingerprints remain unchanged during a lifetime: Once formed the friction ridges only increase in size in due course of time without any change in their pattern throughout the life of an individual until, skin decomposes or an injury is so deep that it destroys dermal papillae.
•  Fingerprints have general ridge patterns that permit them to be classified. The arrangement of friction ridges on the fingers is found in three forms namely loops, whorls and arches. These three pattern forms the basis of fingerprint classification systems used for comparison and keeping record.

5. Fingerprints: fingerprint study involves analysis and comparison of friction ridge patterns present on the anterior surface of the fingers.

5a. Morphology of fingerprint: before defining various types of fingerprint pattern it is important to understand the basic fingerprint features that make up the fingerprint pattern.

• Pattern area: as described above fingerprints are the impression of ridges left behind on the surface. The pattern area is like the outer boundaries of fingerprint pattern in which core, delta and type lines are present.
• Delta: also known as triradius is that region on the fingerprint where the outer most ridges on the pattern area diverge. This diversion causes a space where other type’s lines exists.
• Type line: Those ridges which are used in classifying the various types of the fingerprint patterns are called as type line.
• Core. As the name implies it approximately the central point of the fingerprint pattern.

5b. Comparison of a Single Fingerprint

The ridges don’t exist as continuous running lines. They can bifurcate or may exist in the form of small dot. All these features are important and used in comparing fingerprints. Matching of minimum 8 ridge features are generally prescribed for proving the similarity of fingerprints. Some of the important features of friction ridges which are used in establishing identity are:

• Short ridge: It is a small sized ridge.
• Dot: It is a small round ridge.
• Bifurcation and Trifurcation: A ridge splitting into two or three ridges respectively is called as bifurcation and trifurcation.
• Enclosure: When a single ridge split in to two and these two forked ridges again converges and continues as a single ridge that formation is called as enclosure or Island.
• Hook or spur: It is a ridge bifurcating in to two but only one of the bifurcations continues ahead.
• Bridge: When a ridge bifurcates into two and one of the bifurcation runs ahead whereas the other bifurcation joins with adjacent parallel ridge an bridge like structure is formed, connecting the two parallel running ridges.
• Ridge Ending: A ridge running between two other ridges and ending up abruptly is called as ridge ending.
• Intersection: Two ridges cutting each other are called as intersecting ridges.

Ridge Count: It is the number of ridges which cut or cross the imaginary line drawn between core and delta constitutes ridge count. Ridge count excludes counting core and delta.

5c. Fingerprint Classification

The type lines on the finger balls exist in the form unique patterns. These patterns are primarily identified as Arch, Loop and Whorls on the basis of absence, presence and number of delta and cores.

• Arch: they are least frequent and simple type of pattern in the human population. Arches are characterized on the basis of absence of both core and delta. They can be further subcategorized as plain and tented arches. In plain arch the type lines can be

seen flowing gently from one side of finger ball to the other whereas in tented arched pattern the slope of the ridge is almost vertical.

• Loop: Loops are the most frequent type of fingerprint pattern. They are characterized by the presence of one delta and one core. Loops can be further subcategorized as radial

loop and ulnar loop on the basis of slanting of ridges towards ulnar or radial direction. If the ridges enter and exist from the little finger side that loop pattern is termed as ulnar loop and if it enters and exist from the thumb side that loop pattern is termed as radial loop.

• Whorls: Whorls are second most common type of fingerprints. They are characterized by the presence of two deltas and one or more core. They can be further sub-classified as Plain Whorl, Double loop, Central pocket loop and Accidental. The plain whorl is the simplest type of whorl having two deltas and one core. The type lines are arranged either in circular or spiral fashion around the core giving it the image like that of disturbance of water in the pond after being hit by the pebble. Central pocket loop also posses two delta and single core. The central loop prints look like a loop print having a whorl in the central position. It can be differentiated from the plain whorl on the basis of positioning of deltas. If the imaginary line joining the two delta cut across the ridges encircling the core then the pattern is plain whorl and if does not cross through the ridges forming circle around the core then the pattern is classified as Central loop whorl. Double loop also known as lateral loop or composite whorl or twin is the combination of two loops. These two loops may open in same direction or in opposite direction. Accidental whorl is the pattern which cannot be classified in any of the above mentioned categories. They may have two or more than two deltas and often exist as various combinations of loops and whorls.

Once Fingerprints are developed and identified as various types the next step is to carry out the comparison of fingerprints. The main purpose of comparison is to identify a person from his or her fingerprint. To collect information the fingerprint from the scene of crime or from the suspect is first collected on a ten print card or on a live scan (digital version of then print card). Although the use of technology for recording and compiling has made the task of classification easy but given the vast amount of already existing fingerprints record and matching it with that of fingerprint under study can still be a daunting task. To ease the process of fingerprint comparison Sir Edward Henry developed the first alphabet–numeric system of fingerprint classification. Henry’s System of classification consisted of four divisions namely, Primary, Secondary, Sub-secondary and Final to which later on Key and Major system of classifications were added.

5d. Henry’s Classification System

•  The primary classification:

The ten print card has blocks written in sequence staring with right thumb to right little finger to left thumb to left little finger. Each block is assigned a number starting with 1 to right thumb to 10 to left little finger.

For the purpose of classification first of all examine each fingerprint on the ten digit card and determine their types. In this classification only whorls are identified and all types of whorl are categorized as Whorls. The first two boxes that is box 1 and 2 having the fingerprint impression of right thumb and right index finger are assigned the value of “16” if the whorl pattern occurs in it. In case of loop and arch “0” value is given. Similarly value of “8” is given to the next two block “3” and “4” followed by “4” to next two. Box number 7 and 8 has value “2” and to the last two 9 and 10 the value is “1”. The formula for primary classification is

Sum of all Even digit Henry value +1 Or R Index Ring + L thumb+ L Middle+ Little+1

———————————————————————————–                                                    Sum of all odd digits henry value +1 R Thumb+ R Middle Little Index+LRing+1

• Secondary Classification: It is based on the pattern of right and left Index finger. Capital letters are assigned to denote the pattern type. “A” is used for both plain and tented arch, “W” is used for all types of whorls however “R” is used for radial loop and “L” is used for ulnar loop. Right index finger pattern is placed in numerator and left in denominator. The small letters “a, t and r” are used for arch, tented arch and radial loop to designate pattern if they occur on the thumb or the middle finger. Middle finger pattern is represented in small letter on the immediate right side of the index finger pattern and finger print pattern is shown on the immediate left side of the index finger.

Sub-secondary classification: It is done keep in consideration the pattern type and ridge count on the index, middle and ring fingers. Arches on these fingers are not included. In Secondary classification the ridge count and trace are converted into letter and that letter is depicted.

For loops the following conversion is followed

Finger	Inner (I)	Outer
Index	01 to 09 RC*	10 above RC
Middle	01 to 10 RC	11 above RC
Ring	01 to 13 RC	14 above RC

*RC=Ridge Count

For whorl, ridges are traced from the left delta to right delta direction. The ridge originating or appearing adjacent to delta is traced. The number of intervening ridges between the traced ridge and right delta is counted and following conversion is applied.

Finger	Inner (I)	Meet (M)	Outer (O)
Index/ Middle/ Ring	3  or  more  ridges inside the right delta	Less  than  3  ridges inside or outside the rigth delta	3  or  more  ridges outside the right delta

In addition to sub-secondary system, sometime Second sub-secondary system is used which follows another system of conversion

• Major: The major classification is based on the ridge count converted into letter for the Major classification can only be done in case of presence of loop or whorl pattern type on thumb. In case of arch, there will be no major classification. In major classification ridge count of left hand determine the conversion system for right thumb therefore ridge count of left thumb is done first

When the whorl appear on the left thumb then smaller conversion chart that is ridge count for less than 17 ridges are used for right thumb.

• Final classification: for final system of classification only the loops appearing on the little finger is used. First right finger is examined for the presence of loop, if present its ridge count is mentioned as numerator however if loop does not exist on the right little finger then left little finger is examined for loop, if presents its ridge count is mentioned as denominator. If neither right nor left little finger bear loop pattern then final classification is not done and if both the little fingers have loop then only right finger ridge count is mentioned. In rare case final classification is also done on the basis of whorl pattern on the little finger. However the rules are for counting the ridge count is different.
• Key: consist of the ridge count of the first loop that appears on the ten print cards. Loop pattern on the little finger is not counted as it is used in the final classification. If none of the finger bear loop then key classification system is dropped. The key is always represented as numerator.

The sequence for displaying the 10 digit classification system is

KEY-MAJOR-PRIMARY-SECONDARY-SUBSECONDARY-FINAL

6. Palm Print: Palm prints are equally important as fingerprint as they can be used for establishing identity.

6a. Morphology of Palm prints

The palm print has same ridge features (ridge end, enclosure, bifurcation etc.) like fingerprint but differs from fingerprints in having variety of creases. The palmer region is subdivided in to three region namely, inter-digit, hypothenar and thenar. The interdigital region is the palmer region just under the fingers. It is further sub-divided into volar pad (VP) II, III and VI. The VP II is the region between the index and middle fingers. The VP III region is between the middle and ring fingers and VP VI is the region between last two fingers.

For the purpose of formulation of main line, the palm is divided into 13 region and symbols and number are assigned to each region. The inter-digital region is characterized by the presence of deltas named as “a”, “b”, “c” and “d” in radio-ulnar sequence. The radiant line emerging from these triradii are further termed as A, B, C and D. These radiant line traced to find out in which region of the palm it ends accordingly its number are assigned which constitutes main line formula. The formula is recorded in the order of D-C-B-A. Another prominent delta known as “t” triradius is also found occurs in the proximal region of palm, at the imaginary intersection of hypothenar and thenar regions.

Hypothenar : the hyothenar is the area that lies towards ulnar portion of the palm. The elevation in this region is termed as hypothenar eminence. Volar pad I exist in the hypothenar region between index finger and thumb. Likewise the area that lies towards the thumb portion is called as the thenar having thenar eminence. Verities of patterns are found on hypothenar and comparatively lesser pattern exists on thenar eminence just like finger prints.

Latent prints or fragmentary prints which are routinely encountered at the scene of crime are analyzed by trained and skilled experts who developed a sense of judgment in identifying the region and patterns with their experience. For matching of complete palm prints or for personal identification record purpose main line formula is derived.

7. Sole Prints: The friction ridges on the sole of the feet are as important as friction ridges on finger and palm. Like the finger and palm prints sole prints are also used for personal identification and identification of latent prints. However, the difference in ridge flow and pattern types leads to formulations of different type of classification system for prints from the plantar surface (Sole) of the foot.

7a. Morphology of Plantar Surface

Just like palmer surface, the plantar surface can be divided into eight areas that help in the classification of prints:

Directions: Distal region is the area towards the toes whereas proximal region is area towards the heel. The region of the foot towards the inner side of the body is Thenar while the region towards out side of body is hypothenar

1. Hallucal : Hallucal area consist of inter digital area I ( area between great toe and long toe) and the distal thenar area. The area consist of verity of patterns like loops, whorls an arches. The remaining three interdigital areas namely II, III, and IV are the regions between long toe and third toe, third toe and fourth toe and finally between fourth and little toe respectively. The interdigital areas bears triradii/ deltas and have same designation as “a” , “b” , “c” and “d” for the deltas existing under long toe, third toe , fourth toe and little toe respectively. However, sole print also have a triradius designated as “e” under the great toe, which has no corresponding triradius in the palm.
2. Hypothenar: The region of the foot towards outer side of the body is called as hypothenar. Depending on its direction towards proximal and distal region, it is further categorized as distal and proximal hypothenar. Mostly horizontally flowing ridges occur in these regions.
3. Thenar : The region of the foot towards the inner side of the body us called as the thenar or tibila thenar region and follow the same classification as hypothernar region into distal and proximal areas of foot. The region bears large number of creases and has similar ridge patterning like hypothenar area. Interestingly, wedge shaped ridge flow pattern occurs very frequently on the proximal thenar region towards the beginning of heel region.
4. Calcar: Calcar is the heel region. Straight horizontally flowing ridges are found on this region and rarely any pattern is seen.
5. Toes: Just like fingerprints toe prints also exhibit patterns like arches, whorls and loops however, they differ from fingerprints in the frequency distribution of pattern types. Arches are the more common found followed by loops and whorls on the toes.

Though sole prints were being used for identification purposes for over hundred years but recent knowledge on the sole print is still limited. Latent sole prints of small size are are usually confused with palm prints. Recording the prints also poses another problem as big toe is generally flat and only tips can be recording in case of other toes. Nevertheless, sole prints are as important as friction ridges prints from the other surfaces of the body and research should be conducted to strengthen this area of science.

Summary

Dermatoglyphics is the scientific study of prints or impressions formed from the surface of palm, fingers, sole and toes. These impressions are formed when perspiration discharged from the sweat  glands along with dead skin cells, proteins, fats, and material creates impression of the ridges on the surface of contact. The friction ridges first appears between 12th and 16th week of gestational age of embryo and estimated to be complete by 24th week of gestation. The prints are unique, permanent and can be classified. Fingerprints bears important features such as core and delta which are used in its classification as arch, loop and whorl patterns. Apart from this,specific ridge features called as minutiaes can be analyzed for comparison and identification purpose. To ease the process of fingerprint comparison with many recorded prints, Henry’s system of classification was formulated which consist of divisions namely, Primary, Secondary, Sub-secondary, Final, Key and Major system. Palm prints are equally important as fingerprint as they can be used for establishing identity. Identification of main line formula is one the popular method of palm print analysis. Another important category of dermatoglyphic prints is sole print. Like the finger and palm prints, the sole prints are also used for personal identification and analysis of latent prints. However, the difference in ridge flow and pattern types leads to formulations of different type of classification system for prints from the plantar surface (Sole) of the foot.