Henry’s Ten-Digit Classification of Fingerprints
Fingerprints are considered someone’s visiting card, which confirms the individuality of a person. These prints are always left by a person at any place as explained in Locard’s exchange principle and on any surface unknowingly unless he/she has worn gloves.
Fingerprints are the impressions produced by the pattern of ridges and furrows present on the tips of a human’s fingers. The ridges are produced by the tiny pores of the skin which are aligned in different line patterns. These patterned lines or the friction ridges together form a single finger impression.
The fingerprints are very detailed, permanent, unique, and universal, therefore they are considered one of the important identity markers for human identification. The application of fingerprints in forensics is based on three basic principles:
- The fingerprints of every individual are unique. Even identical twins have different fingerprints.
- The finger impressions are permanent throughout the lifetime of an individual. They cannot be altered by any means.
- The ridge patterns of the fingerprints can be easily classified.
The fingerprint is a very broad subject that is beyond this article. Here in this article, only the classification of fingerprints is discussed.
Classification Systems of Fingerprints
With the discovery of fingerprints, forensic science got a new direction for the identification of criminals. One of the important aspects of fingerprint examination is classifying fingerprints.
The earlier classification of fingerprints was developed by Johannes Evangelist Purkinje in 1823. He described nine classifiable fingerprint patterns:
- Transverse curve
- Central longitudinal stria
- Oblique stripe
- Oblique loop
- Almond whorl
- Spiral whorl
- Double whorl.
The next classification system was proposed by Dr. Henry Faulds in the 1880s. He devised a method of using ink to record the fingerprint impressions of all 10 fingers on cards and soon had collected thousands of fingerprint cards.
In Henry’s classification, each hand was represented by five syllables, one syllable for each finger, with each syllable separated by a hyphen. Syllables were constructed from an established list of 21 consonants and 5 vowels representing a set of fingerprint pattern characteristics.
Followed by Faulds, Sir Francis Galton, cousin of Charles Darwin published a book on fingerprints named FingerPrints in 1892. In his book, Galton formulated a classification system that was based on the alphabetical enumerations of the three fingerprint patterns where ‘L’ represented a loop, ‘W’ represented a whorl, & ‘A’ represented an arch.
The modern fingerprint classification system was started with the work done by Juan Vucetich in 1891. He initially called his system ‘icnofalangométrica‘, meaning “finger track measurement”. In 1896, he renamed the system ‘dactiloscopía‘, meaning “finger description”.
The classification consisted of four single letters, representing the pattern on the thumb, and four single numbers, representing the patterns on the remaining fingers. The Vucetich classification system consisted of a basic primary classification and a more descriptive secondary classification using extensions.
The primary classification divided the prints into the numerator (termed as series and represents the right hand) and denominator (termed as sections and represents the left hand). The secondary classification further subdivided the fingerprints into five subtypes i.e., 5, 6, 7, 8, and 9. Each number represented a further description of the pattern, applied to either hand, and was placed as a superscript in parentheses.
The classification which is followed at present is known as Henry’s ten-digit classification. This method was devised by Sir Edward Henry in 1896.
How Henry’s Classification Was Developed?
Sir Edward Richard Henry was the new Inspector General of the Bengal District Police in India in the early 1890s and was experiencing a common problem of the day: the inability to accurately identify the native people.
Henry was very much influenced by Galton’s book named FingerPrints. He went back to England in 1894, where he developed personal and professional relationships with Galton and learned a lot about fingerprints. In January 1896, Henry ordered the Bengal Police to collect prisoners’ fingerprints in addition to their anthropometric measurements.
Henry assigned two of his police officers from the Calcutta Anthropometric Bureau to work on the fingerprint classification project. By 1897, the two officers, Azizul Haque, and Hem Chandra Bose formulated a mathematical method of dividing fingerprint records into a large number of primary groupings that were based on Galton’s fingerprint pattern types.
Henry’s 10 Digit Fingerprint Classification
Henry’s classification is carried out by the following steps:
- Primary Classification– The classification starts with the primary classification which is a 10-finger system. The fingers on each hand are given an identifying number. Starting with the right thumb, the fingers on the right hand are numbered from 1 to 5. On the left hand, starting from the thumb, they are numbered 6 to 10. Each finger is given a value only if it has a whorl design and if the finger has an arch or loop, it is given a value of zero. Not all fingers are given the same value if they have a whorl.
|Fingers (right)||Thumb||Index finger||Middle finger||Ring finger||Little finger|
|Value if whorl||16||16||8||8||4|
|Fingers (left)||Thumb||Index finger||Middle finger||Ring finger||Little finger|
|Value if whorl||4||2||2||1||1|
This classification is expressed in ratio form, with the numerator representing the whorl values of the even fingers plus 1 and the denominator representing the whorl values of the odd fingers plus 1. It is given by:
(1 + sum of even finger values) / (1 + sum of odd fingers)
This system allows the classification of fingerprints into 1024 groups. Approximately 25% of the population has a 1/1 primary classification. This means that they have either all loops or all arches, or a combination of loops and arches.
- Major division classification– It is the next step which uses only the thumb of both hands. The ridge count of the whorl pattern is conducted and then classified as I(number of ridges is 12), M(number of ridges is 13-19), and O(number of ridges is 20 or more) patterns.
- Secondary classification– It is determined by the pattern types in the index fingers of both hands and is shown in the formula by capital letters representing the pattern (A for arch, T for tented arch, R for radial loop, U for ulnar loop, and W for whorl). While the rarity of arches, tented arches, and radial loops in non-index fingers, these patterns are indicated by lowercase letters (a, t, r).
- Sub-secondary classification– This classification represents the ridge counts for loops or ridge tracing for whorls in the remaining fingers.
- Final classification– In this step the little fingers are considered and ridge counting of the loop patterns is carried out.
Acceptability of The System
Henry’s classification system is the most accepted method for classifying fingerprints. It is widely used in today’s modern fingerprint examination methods. Soon after this method was developed, Scotland Yard reviewed its identification system which resulted in the abandonment of Bertillonage and started following Henry’s classification system.
From there it gradually spread to various other nations and now it is accepted and used by all the nations as the most appropriate method of classification of fingerprints.
Unfortunately, it could only accommodate files of up to 100,000 sets of prints, after which, it became too cumbersome. The FBI further modified the system by adding additional extensions but the first step in classification is essentially the same.
The modern technologies of the Integrated Automated Fingerprint Identification System(IAFIS) use Henry’s system of classification.
Fingerprints are one of the most reliable forensic evidence that can easily reveal the identity of an individual. One of the methods of fingerprint analysis involves the classification of fingerprints. When we dig into the history of fingerprint classification, the results will give several systems of fingerprint classification proposed by different scientists.
However, the most promising method used by modern-day scientists is Henry’s ten-digit Classification system, proposed by Sir Edward Henry.
This system is also applied to present-day fingerprint biometric databases such as AFIS or IAFIS.
Also Have a Look at:
- Personal Identification Using Lip Prints In an Investigation
- Footprints as Evidence in Criminal Investigation
- How Gait Pattern Helps in Identification?