Q4 LONG ANSWER 10M ★ High-yield

Describe dactylography with the properties, patterns and uses of fingerprints. Add a note on other prints.

Forensic Medicine · 2nd Professional — Para-Clinical

Dactylography — Principles

Dactylography (dermatoglyphics, dactyloscopy) is the study of fingerprints — the patterns formed by the epidermal ridges on the palmar surface of the terminal phalanges — for the purpose of identification. It is the most reliable method of identifying a living person.

Four properties make it definitive:
(1) uniqueness — no two individuals, including monozygotic twins, have identical fingerprints, because the ridges are formed by local mechanical and vascular factors in fetal life rather than by genotype alone. This is what distinguishes fingerprints from DNA, which identical twins share
(2) permanence — the ridges are formed by the 3rd to 4th month of intrauterine life, are fully developed by birth, and remain unchanged throughout life and until decomposition destroys the skin. They enlarge with growth but the pattern does not change
(3) They cannot be permanently destroyed — superficial injury, burns and abrasions heal and the pattern regenerates, because it is determined by the dermal papillae. Only destruction of the dermis by a deep burn or a deep incision produces a permanent scar, and the scar itself then becomes an identifying feature
(4) They are readily classifiable and searchable, which is what makes a national database possible

Pattern	Frequency and features
Loops	About 60–70% — the commonest. Ridges enter from one side, curve, and return to the same side. Ulnar loops (opening toward the little finger) are far commoner than radial. One delta
WHORLS	About 25–30%. Circular or spiral ridges with two deltas
Arches	About 5–10% — the least common. Ridges run from one side to the other with a slight rise; plain and tented types. NO delta
Composite	About 1–2% — combinations: central pocket loop, twinned loop, lateral pocket loop and accidental

Identification rests on the minutiae (Galton details) — ridge endings, bifurcations, islands, lakes, spurs and crossovers. Traditionally 8 to 16 matching points with no unexplained difference were required in India for a positive identification, though modern practice is moving toward a holistic rather than a numerical standard
Historical development — Sir William herschel used fingerprints administratively in Bengal from 1858; Sir Francis GALTON established their uniqueness and permanence and devised a classification; and Sir Edward HENRY, with AZIZUL HAQUE and HEM chandra BOSE in Bengal, devised the HENRY system of classification. The world's first fingerprint bureau was established in calcutta in 1897
Types of print found at a scene — latent (invisible, from sweat and sebum, developed with powders, ninhydrin, iodine fuming, cyanoacrylate or laser); visible (patent), in blood, ink, grease or paint; and plastic, impressed into a soft material such as wax, soap or putty

CLINICAL PEARL

Fingerprints distinguish identical twins and DNA does not — which is why the older method has not been superseded. Monozygotic twins share a genome, so a standard DNA profile cannot separate them. But ridge patterns are shaped by local events in fetal life — pressure, blood supply, the position of the volar pads — so they differ even between twins. The two methods are complementary rather than competing, and each covers the other’s principal weakness.

Other Prints

Print	Features and use
Palm prints and sole prints	Ridge patterns as individual as fingerprints; sole prints of newborns are routinely taken in hospitals to prevent the interchange of infants
Foot prints and the walking pattern	A barefoot print at a scene gives ridge detail; a shod print gives the shoe. The gait pattern — the line of walk, the length and breadth of stride, and the foot angle — may indicate height, sex, load carried, whether the person was running, and any limp
Lip prints (cheiloscopy)	The grooves on the vermilion of the lips are individual and stable; classified by Suzuki and Tsuchihashi. Found on glasses, cigarette ends and cloth
Palatal rugae (palatoscopy)	Individual and highly resistant, being protected by the tongue, teeth and lips — so they survive fire and trauma and are useful in mass disaster
Ear prints	Left when an intruder listens at a door; individual, though the evidential value is disputed
Bite marks	Forensic odontology — found on the victim in assault and sexual offences, on the assailant from a defending victim, and on foodstuffs at a scene. Photographed with a scale, swabbed for saliva DNA before anything else, and compared with dental casts
Poroscopy and edgeoscopy	Identification from the arrangement of sweat pores on the ridges (Locard), and from the ridge edges — used where only a small fragment of a print is available

Recording and Comparison of Prints

From a living person — the fingers are cleaned and dried, inked evenly, and rolled from nail edge to nail edge to capture the whole pattern including both deltas; plain (dab) impressions of all four fingers and the thumb are taken alongside as a check on sequence
From the dead — the fingers are cleaned and dried; in rigor mortis the fingers are straightened by breaking the rigor or by severing the flexor tendons; in maceration or early decomposition the fingertips are injected with glycerine, saline or tissue builder to restore turgor; and in advanced decomposition the epidermal skin is degloved and mounted on the examiner’s own gloved finger to take the print. In burnt bodies the flexed fingers protect the pads and prints are often obtainable
Latent prints at a scene are developed with fine powders (aluminium, black, magnetic) on non-porous surfaces; ninhydrin and DFO for amino acids on paper and porous surfaces; iodine fuming, which is transient and non-destructive; cyanoacrylate (superglue) fuming for non-porous surfaces; silver nitrate; and laser or alternate light sources
The print is then lifted with tape or photographed with a scale, and compared against a suspect’s prints or searched in the database
Comparison proceeds by pattern type first, then ridge counting and tracing, then the minutiae — and an identification requires agreement in sequence and spatial relationship with NO unexplained difference. A single genuine discrepancy excludes, however many points agree

Applications and Applied Aspects

Criminal investigation — comparison of a scene print with a suspect and with a database; India's NAFIS (National Automated Fingerprint Identification System) maintains a national searchable database
Civil and administrative uses — the aadhaar system, which has enrolled the fingerprints and iris of most of the Indian population; thumb impressions on documents and wills by the illiterate; verification of pensioners; and prevention of impersonation in examinations and elections
Identification of the dead, where the skin is preserved — and prints can be obtained from macerated or decomposed hands by injecting the fingertips to restore turgor, or by degloving and mounting the skin
Taking prints from a body requires care and permission; the hands should be protected with paper bags at the scene to preserve both prints and any trace material under the nails
Prints can be FORGED or planted, and a print proves only that the finger touched the surface — not when, and not that the person committed the offence. A doctor or investigator should not overstate what a print establishes
Swab a bite mark for saliva DNA before photographing or casting it; washing, swabbing late or applying anything to the wound destroys the most valuable evidence it carries
Protect the hands with paper bags at the scene and at the mortuary; this preserves both the fingertips and any trace material beneath the nails
Prints can be obtained from decomposed hands by injecting the fingertips or degloving the skin, so a macerated body should never be assumed unprintable without trying
Roll the print from nail edge to nail edge; a dab impression misses the deltas and may make classification impossible
One unexplained difference excludes, however many points agree — which is why fingerprint comparison is an exclusionary discipline before it is an identifying one
A print proves contact, not culpability, and it carries no date; a doctor or investigator should never state more than that the finger touched the surface
Fingerprints separate identical twins and DNA does not, which is why the older method has not been superseded and why both are used together
Deep dermal injury permanently alters a print, but the resulting scar becomes an identifying feature in itself — attempts to destroy prints defeat themselves
Sole prints of newborns are taken routinely in maternity units to prevent interchange of infants, which is a real and recurring problem
Palatal rugae survive fire because they are protected by the tongue, teeth and lips, and are a useful identifier in burnt bodies where the face has gone
Straighten the fingers of a rigid body by breaking rigor or dividing the flexor tendons; an unprintable hand is usually a technique problem rather than a real obstacle
The first fingerprint bureau in the world was in Calcutta in 1897, and the Henry system was developed there by Henry with Azizul Haque and Hem Chandra Bose
Iodine fuming is transient and non-destructive, so it is used first where a document must be preserved for other examination
Cyanoacrylate fuming works on non-porous surfaces and ninhydrin on paper; choosing the wrong developer can destroy the print irreversibly
NAFIS gives a national searchable database, so a scene print now has value even where there is no suspect to compare it with
Aadhaar has enrolled fingerprints and iris nationally, which has changed both civil identification and, in practice, the identification of unknown bodies
Bite marks carry saliva DNA, and swabbing before any other handling recovers evidence far stronger than the mark itself
Poroscopy and edgeoscopy salvage fragments too small for conventional comparison, using sweat pore arrangement and ridge edges
Lip prints and palatal rugae are individual too, and both survive circumstances that destroy the face — cheiloscopy on glasses and cigarette ends, palatoscopy in burnt bodies

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