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Fingerprinting is the mainly cost-efficient technique for suspect identification. The fingers of a person consist of small ridges which are totally natural. These ridges, even though they are genetic in nature, develop as the child is growing in the womb. As the foetus stretches or bends his/her fingers, stretching the skin results to forming of ridges on fingers. The ridges form a pattern that is unique to each individual. Those ridges contain sweat pores from which are excreted perspiration, salts and oils. The oils that are left on a surface are known as latent fingerprints.
Edward Henry acknowledged that fingerprints could be described as having three basic pattern –
Arches
Loops
Whorls
Arches – Arches occurs about 5% of fingerprints of all patterns around world. In this form the ridges of the finger flow constantly from one end of the finger to the other and make no reverse turn. Usually, there is no delta in an arch pattern but even if delta exists, still there will be no reverse curving of ridges which intervenes between the core and delta point. This type of pattern most commonly found on the index finger, respective on the middle finger and thumb, and least commonly on the ring finger and pinky finger. However, Arches are most commonly found in Africa, North Europe and the West Caribbean area; and less commonly found in East Asia and the Pacific Islands near Australia.
Arches are further divided in following two patterns:
Plain Arch – In this type there is constant flow of ridges. It starts from one end of the finger, and then slightly bend upward, which almost resemble like a wave out on the ocean. The plain arch continues towards another end of the finger. It is the simplest of the fingerprint patterns.
Tented Arch – This pattern is similar to plain arch as in initial stage it starts from one end of the finger and flows out in similar way to the other side. The only difference in the tented arch lies in the centre of ridges, which are not continuous as in the case of the plain arch. The ridges adjoin each other at the centre, converge and thrust upward, which gives an impression of tent like structure.
Loops – Loops fingerprint pattern is most common type of fingerprint pattern, it occurs in about 60-70% fingerprint patterns. In this pattern one or more ridges start from either end of pattern, re-curves, touches or intersects the ridges running from the delta to the centre and ends on or in the direction where the ridges started. Each loop pattern consists of one delta and one core in it.
This pattern is further sub-divided in following patterns:
Radial Loop – The name of radial loop fingerprint pattern, is named after the radius bone (a bone which joints the forearm and present at the side as the thumb). In this fingerprint pattern, the ridges flow from one end towards the centre of the fingertip and re-curves toward the radius bone end, after forming a loop like structure at the centre of fingertip. Radial fingerprint is not very common and mostly this type of pattern is found on thumb.
Ulnar Loop – The name of this pattern is named after the ulna bone (a bone in forearm present at the side of little finger). The ridges in this pattern start from the side of ulna bone, flow towards the centre and re-curves towards the same end; forms a loop like structure at centre. Same as the radial pattern it is not very common and most likely to be found on thumb.
Whorls – Whorls type of fingerprint pattern occurs about 25-35% as it is second common fingerprint pattern. In this pattern ridges on fingertip make curves which results to form at least one circuit. In whorls there are two deltas, one at each side of circuit. When fingerprints have two or more deltas, then that fingerprint will be of a whorl pattern.
Plain Whorls – In plain whorls, ridges flow from one end to another end of finger on upper side, while in centre part on finger one or more ridges form circuit. If an imaginary line is drawn between two deltas it can be seen that at least one of the ridges re-curving in interior area cuts each other or just touch each other.
Central Pocket Whorls/Peacock Eye Whorls – In central pocket whorl pattern re-curving of the ridges can be found at least once and it consist of two deltas at either side of the re-curving. A right angle can be drawn through both the deltas. In this pattern ridges do not cutting or touching is there. Ridges re-curving form a complete circuit which may be of any variant of a circle. It also called as Peacock Eye Whorl, as it gives resemblance to peacock eye.
Accidental Whorls – In accidental whorls pattern there are two different types of pattern, in which one is usually plain arch. It is the only pattern in which more than two deltas can be seen is exceptional cases. This finger contains such pattern which does not covered by none of the definition.
Latent Fingerprint Development – Latent fingerprint development means developing or make visible those fingerprints which are not visible or those which cannot easily seen by unaided eyes. Latent fingerprint development is done through various technique, which are optical processes, physical processes and chemical processes, most of these techniques have been evolved during the time period of last century. As these techniques are frequently changing and relatively complicated, it is very important that those who are involved in laboratory and crime scene examinations process must be well trained and well-practiced. The safety of those persons who are concerned with laboratory work and crime scene examination, supreme priority, as to lessen the chance of getting exposed to pathogens or hazardous chemicals which is used in laboratory.
Composition – The latent print residue is very complex in composition, there are various chemical compound are present which comprise of latent fingerprint residue, main element of that is sweat and others are organic and inorganic compound which secrets by skin. All these element secrets through the ridges which forms fingerprint at surface. After reacting with chemicals or various other technique the residue can visible to naked eyes. By latent fingerprint development a decade old fingerprint can also be develop by using reagent such as physical developer.
There are various technique which are use in latent fingerprint development, some of them are follows –
Latent Print Powder: This technique involves dusting of powdering or dusting of powder- finely divided in particles, it reacts with aqueous and oily components in latent print; and make fingerprint visible. This is one of the oldest techniques used for detection of fingerprint at crime scene. It traces to last few decades of 18 century.
Ninhydrin and Analogues: This technique was first used in 1910, when Ninhydrin compound was mistakenly prepared by Siegfried Ruhemann. Ruhemann observed that this chemical compound reacts with skins residue and amino acids, form a purple colour. Ninhydrin treatment proved to be excellent for developing latent fingerprints. Several other methods were developed for latent fingerprint development and enhancement for weakly developed fingerprints. In the period of 1970 and 1980 when UV light and laser was became available for forensic experts, enhancement of weak ninhydrin fingerprint become easier.
1,8-Diazafluoren-9-one (DFO) – The 1,8-Diazafluoren-9-one also known as DFO was prepared in year 1950, but the reaction between DFO and amino acid was discovered in the year 1990, when it was first used for latent fingerprint development. The reaction between DFO and amino acid which present in latent fingerprint results faint red or pink colour fingerprint and extremely fluorescent at room temperature. The use of DFO increased rapidly for its results. Now this technique is widely by forensic experts to develop fingerprints.
There are also various other techniques which are also used by forensic experts, namely –
1,2-Indanedione
Methylthioninhydrin (5-MTN)
Cyanoacrylate Fuming
Fluorescence Examination
Aqueous Techniques
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