Unit 1: Introduction to Forensic Dermatoglyphics - Subjective Questions

Dermatoglyphics is the scientific study of the patterns of ridges present on the skin of the fingers, palms, toes, and soles. The term is derived from two Greek words: derma (skin) and glyphe (carving).

Significance in Forensic Science:

• Personal Identification: Fingerprint ridge patterns are unique to every individual, making them a reliable tool for identifying suspects, victims, and missing persons.
• Permanence: Ridge patterns remain unchanged throughout an individual's lifetime (barring deep injury), enabling identification even years later.
• Crime Scene Investigation: Latent prints recovered from crime scenes help link suspects to physical evidence.
• Legal Admissibility: Fingerprint evidence is widely accepted in courts of law across the world.
• Biometric Applications: Forms the basis of modern biometric authentication systems.

Dermatoglyphics thus bridges biology and criminal justice, providing an objective, scientific basis for identification.

The development of dermatoglyphics internationally involves several pioneering scientists:

• Nehemiah Grew (1684): Presented the first scientific paper describing ridges, furrows, and pores on the hands to the Royal Society.
• Marcello Malpighi (1686): An Italian anatomist who studied ridges and pores under a microscope; the Malpighian layer of skin is named after him.
• Johann Christoph Andreas Mayer (1788): First to state that fingerprint arrangements are unique to individuals.
• Jan Evangelista Purkinje (1823): Classified fingerprint patterns into nine categories but did not link them to identification.
• Sir William Herschel (1858): First to use fingerprints for identification in official documents in India.
• Dr. Henry Faulds (1880): Suggested the use of fingerprints for criminal identification and published in Nature.
• Sir Francis Galton (1892): Published the book Finger Prints, establishing the individuality and permanence of prints and identifying the minutiae (Galton details).
• Sir Edward Henry (1897): Developed the Henry Classification System used worldwide.

These contributions collectively transformed fingerprinting into a scientific discipline.

India has played a pioneering role in the development of fingerprint science:

• Sir William Herschel (1858): While serving as a British administrator in Bengal, India, he began using fingerprints (handprints) on contracts and legal documents to prevent fraud and impersonation. This is considered the first systematic official use of fingerprints.
• Azizul Haque and Hem Chandra Bose: Two Indian officers working under Sir Edward Henry at the Calcutta Anthropometric Bureau. They developed the mathematical basis and classification formula for the Henry Classification System, though Henry received primary credit.
• Establishment of the First Fingerprint Bureau (1897): The world's first Fingerprint Bureau was established in Calcutta (Kolkata), India, marking the formal beginning of fingerprint-based criminal identification.
• Central Fingerprint Bureau (CFPB): Later established to maintain national fingerprint records in India.

Thus, India was central to the birth and standardization of modern fingerprint science.

Friction ridges are raised portions of skin on the fingers, palms, and soles. Their biological formation involves the following:

Skin Structure:

• The skin has two main layers: the epidermis (outer) and the dermis (inner).
• Between them lies the basal layer / Malpighian layer, which is crucial for ridge formation.

Formation Process:

• Ridges begin forming during fetal development, around the 10th to 16th week of gestation.
• The volar pads (raised swellings of tissue) develop on the fingertips and palms.
• The size, shape, and regression timing of these volar pads determine the eventual ridge pattern (arch, loop, or whorl).
• Ridge formation is influenced by genetic factors and random intrauterine environmental factors (pressure, blood flow, nutrition, position in the womb).

Permanence:

• Once formed, the ridge patterns in the dermal papillae become permanent. Even if the epidermis is damaged superficially, the ridges regenerate identically from the basal layer.

This combination of genetic and environmental influence explains why even identical twins have different fingerprints.

Fingerprint formation is a developmental process that occurs before birth:

Timeline of Development:

• 6th–7th week: Volar pads (mounds of tissue) appear on the fingertips.
• 10th–16th week: Ridges begin to form as the volar pads start to regress.
• By 24th week (approx. 6 months): Ridge patterns are fully formed and permanent.

Key Factors Governing Formation:

• Volar Pad Shape & Timing:
  • A high, symmetrical pad with early regression tends to produce a whorl.
  • A low pad tends to produce an arch.
  • An intermediate/asymmetrical pad produces a loop.
• Genetic Influence: Determines the general pattern type and overall ridge structure.
• Environmental Influence (in utero): Factors like fetal position, blood pressure, amniotic fluid pressure, and nutrition cause the minute variations (minutiae) that make each print unique.

Outcome: Because of the random environmental influences, no two fingers—even on the same person or on identical twins—have identical prints. Once set, the pattern remains constant for life.

Fingerprint identification rests on three fundamental scientific principles:

1. Principle of Individuality (Uniqueness):

• No two fingerprints—whether from different individuals or different fingers of the same person—are exactly alike.
• Even identical twins have distinct fingerprints.
• This is the foundation of positive identification.

2. Principle of Permanence (Persistence):

• Fingerprint patterns form before birth and remain unchanged throughout life until decomposition after death.
• Superficial injuries heal without altering the pattern; only deep scarring that destroys the dermal layer causes permanent change.

3. Principle of Perennial Nature / Constancy:

• The ridge patterns remain constant in their configuration and relative arrangement.
• The details (minutiae) do not change position or type over time.

Additional Consideration – Classifiability:

• Fingerprints can be systematically classified into pattern types, enabling efficient storage and retrieval.

Together, these principles establish fingerprints as a scientifically reliable and legally admissible means of identification.

Fingerprint patterns are broadly classified into three main types (with subtypes):

1. Arches (approx. 5% of patterns):

• Ridges enter from one side, rise in the center, and exit on the other side.
• Subtypes:
  • Plain Arch: Smooth wave-like rise.
  • Tented Arch: Has a sharp upthrust or spike in the center.
• Arches have no delta and no core.

2. Loops (approx. 60–65% – most common):

• Ridges enter from one side, curve around, and exit from the same side.
• Must have one delta and one core.
• Subtypes:
  • Ulnar Loop: Opens toward the little finger (ulna bone).
  • Radial Loop: Opens toward the thumb (radius bone).

3. Whorls (approx. 30–35%):

• Ridges form circular or spiral patterns.
• Have two or more deltas.
• Subtypes:
  • Plain Whorl: Concentric circles.
  • Central Pocket Loop Whorl: A loop with a small whorl at the center.
  • Double Loop Whorl: Two separate loop formations.
  • Accidental Whorl: Combination of two or more pattern types.

This classification forms the basis of the Henry system of fingerprint categorization.

Both are subtypes of loop patterns but differ in orientation:

Key Point: The classification depends on the hand, since the flow direction relative to the thumb/little finger reverses between the left and right hands. Both types share the essential loop features—one delta and one core.

Ridge characteristics, also called minutiae or Galton details, are the specific ridge formations used to individualize fingerprints. Major types include:

• Ridge Ending: The point where a ridge abruptly ends/terminates.
• Bifurcation: A single ridge splits (forks) into two ridges.
• Ridge Dot (Island): A very short ridge resembling a dot.
• Short Ridge (Island): A ridge longer than a dot but short in length.
• Enclosure (Lake): A ridge bifurcates and then rejoins to enclose a small space.
• Spur (Hook): A short ridge branching off a longer ridge.
• Bridge: A small ridge connecting two parallel ridges.
• Crossover: A short ridge crossing between two parallel ridges.
• Trifurcation: A single ridge dividing into three ridges.

Importance:

• These minutiae, along with their type, position, and orientation, form the basis of point-by-point comparison.
• A match of sufficient minutiae points (traditionally 8–16 depending on jurisdiction) establishes identity.

The uniqueness of the arrangement of these characteristics makes each fingerprint distinctive.

Poroscopy is the study of the sweat pores located along the friction ridges of the skin, used as a means of personal identification. It was introduced and developed by Dr. Edmond Locard in 1912.

Basis of Poroscopy:

• Each friction ridge contains numerous sweat pores (openings of sweat glands).
• The number, size, shape, position, and relative arrangement of these pores are unique to each individual and permanent.

Significance:

• Fragmentary Prints: Extremely useful when only a small portion of a fingerprint is recovered, where full pattern comparison is not possible.
• Additional Corroboration: Provides supplementary evidence to confirm identity when minutiae points are limited.
• High Individuality: Since pores are numerous and uniquely arranged, they add strong discriminating power.
• Permanence: Pore characteristics remain constant throughout life.

Limitations: Requires very high-quality, clear prints since pores are minute and easily obscured by pressure or poor development.

Edgeoscopy is the study of the shapes and contours (edges) of the friction ridges as a means of personal identification. The term was coined by Salil Kumar Chatterjee (1962).

Basis of Edgeoscopy:

• The edges of friction ridges are not perfectly straight; they have irregular characteristics and shapes.
• These edge shapes are classified into forms such as: straight, convex, concave (peak), table, pocket, angle, and others.
• The arrangement of these edge shapes is unique to each individual.

Significance in Fingerprint Examination:

• Individualization: Adds another layer of unique characteristics beyond pattern and minutiae.
• Partial Prints: Helpful when working with fragmentary or incomplete prints.
• Corroborative Evidence: Strengthens identification conclusions by supplementing minutiae and poroscopy data.

Limitations:

• Requires very clear, high-resolution prints.
• Edge shapes can be affected by pressure, deposition medium, and surface texture.

Together with poroscopy, edgeoscopy forms part of third-level detail analysis in advanced fingerprint identification.

Both poroscopy and edgeoscopy are third-level detail techniques used for individualization, especially with partial prints.

Common Points:

• Both are supplementary/corroborative methods.
• Both rely on the permanence and individuality of fine ridge details.
• Both are useful when only small ridge fragments are available.

Difference in focus: Poroscopy looks within the ridge (pores), while edgeoscopy looks at the boundaries of the ridge (edges).

Fingerprint residue is the material deposited on a surface when a finger touches it, forming a latent print. Its composition is a complex mixture derived from three types of skin glands plus contaminants.

1. Eccrine Gland Secretions (main source on fingertips – mostly water-based):

• Water (~98–99%)
• Inorganic components: chlorides, sodium, potassium, phosphates, sulphates, ammonia.
• Organic components: amino acids, urea, uric acid, lactic acid, sugars, creatinine, choline.

2. Sebaceous Gland Secretions (transferred to fingers by touching face/hair – oily):

• Fatty acids
• Glycerides
• Wax esters
• Squalene
• Cholesterol

3. Apocrine Gland Secretions (minor):

• Proteins, carbohydrates, and other trace organic matter.

4. External Contaminants:

• Dirt, dust, blood, ink, grease, cosmetics, or other substances the finger has contacted.

Forensic Importance:

• The water and volatile components evaporate over time, affecting print aging.
• Amino acids and lipids are targeted by chemical developers (e.g., ninhydrin reacts with amino acids; physical developers target lipids).
• Understanding composition guides the selection of development techniques for latent prints on different surfaces.

Sir Francis Galton (1822–1911) was a British scientist whose work established fingerprinting as a scientific discipline.

Major Contributions:

• Book "Finger Prints" (1892): The first comprehensive scientific study of fingerprints.
• Individuality: Statistically demonstrated that the probability of two fingerprints being identical is extremely low (approximately 1 in 64 billion), establishing the principle of uniqueness.
• Permanence: Provided evidence that fingerprint patterns remain unchanged throughout a person's life.
• Minutiae (Galton Details): Identified and named the specific ridge characteristics (ridge endings, bifurcations, etc.) used for comparison; these are still called Galton points/details.
• Classification Basis: His work laid the groundwork on which Sir Edward Henry later built the practical Henry Classification System.

Legacy: Galton transformed fingerprints from a curiosity into a rigorous, statistically supported method of identification, earning him recognition as the father of modern fingerprint science.

Fingerprint analysis is conducted at three progressive levels of detail:

Level 1 – Pattern (General/Class Characteristics):

• Refers to the overall ridge flow and pattern type—arches, loops, and whorls.
• Includes the general orientation, delta, and core positions.
• Used to classify and narrow down candidates; not sufficient alone for individualization.

Level 2 – Minutiae (Ridge Characteristics / Galton Details):

• Refers to specific ridge events: ridge endings, bifurcations, dots, enclosures, spurs, etc.
• The type, position, and orientation of minutiae provide the basis for positive identification.
• This is the primary level used in most fingerprint comparisons.

Level 3 – Fine Detail (Third-Level Characteristics):

• Includes pore positions (poroscopy), ridge edge shapes (edgeoscopy), ridge width, and shape.
• Requires high-resolution, high-quality prints.
• Used for corroboration, especially with fragmentary or partial prints.

Summary: Analysis proceeds from general (Level 1) to increasingly specific (Levels 2 and 3), collectively enabling reliable individualization.

Core:

• The core is the approximate center of a fingerprint pattern.
• It is the innermost point around which the ridges tend to recurve, particularly in loops and whorls.
• Types include the innermost recurving ridge in loops.

Delta:

• The delta is a triangular ridge formation (resembling the Greek letter Δ) where ridges from three different directions meet or diverge.
• It is also called the triradius.
• It is the point of divergence of the type lines.

Importance:

• Classification: The presence and number of deltas determine the pattern type:
  • Arch: no delta.
  • Loop: one delta and one core.
  • Whorl: two or more deltas.
• Ridge Counting & Tracing: The core and delta are the reference points for ridge counting (in loops) and ridge tracing (in whorls), which are essential steps in the Henry Classification System.

Thus, cores and deltas are fundamental landmarks for both classifying and comparing fingerprints.

Fingerprint impressions recovered at crime scenes are classified into three types based on their visibility and mode of formation:

1. Patent (Visible) Prints:

• Visible to the naked eye without any treatment.
• Formed when fingers coated with a colored substance (blood, ink, paint, grease, dirt) touch a surface.
• Can be photographed directly.

2. Latent (Invisible) Prints:

• Not visible to the naked eye; require development to be seen.
• Formed by natural sweat and oil (eccrine/sebaceous secretions) deposited on a surface.
• Made visible using physical methods (powders), chemical methods (ninhydrin, cyanoacrylate/superglue fuming, iodine fuming), or optical methods (alternate light sources).
• Most commonly encountered and forensically important.

3. Plastic (Molded/Impressed) Prints:

• Three-dimensional impressions left in a soft, pliable material.
• Formed when a finger presses into substances like wax, putty, soap, clay, wet paint, or chocolate.
• Visible and can be photographed or cast.

Forensic Relevance: Recognizing the type of impression determines the appropriate recovery and development technique.

Both are subtypes of the arch pattern but differ in their ridge structure:

Key Point: The distinguishing feature is the presence of a significant upthrust or angle in the tented arch, which is absent in the smooth, flowing plain arch. Both lack the recurving ridges of loops and the circular ridges of whorls.

Fingerprints are unique to every individual because their formation is governed by both genetic and random environmental factors during fetal development.

Reasons for Uniqueness:

• Genetic Influence (shared in twins):

  • Identical twins share the same DNA, so they tend to have similar general pattern types (e.g., both may have loops).
  • Genetics governs the broad pattern and overall ridge structure.

• Random Environmental Influence (differs in twins):

  • The exact minutiae—ridge endings, bifurcations, and their positions—are determined by random intrauterine factors.
  • These include fetal position, blood pressure and flow, amniotic fluid pressure, nutrition, and the exact timing of volar pad regression.
  • Even twins in the same womb experience slightly different micro-environments, producing different fine details.

Conclusion:

• While identical twins may share similar Level 1 (pattern) characteristics, their Level 2 (minutiae) and Level 3 (pores, edges) details are always different.
• Therefore, no two fingerprints—even between identical twins—are ever identical, confirming the principle of individuality.

The Henry Classification System is one of the most widely used fingerprint classification systems, developed largely in India.

Sir Edward Henry:

• Inspector General of Police in Bengal, India.
• Led the development of a practical classification system that organized fingerprint records for efficient storage and retrieval.
• The system was named the Henry Classification System and adopted worldwide (including by Scotland Yard and the FBI in its early years).

Azizul Haque:

• An Indian sub-inspector and mathematician working under Henry.
• Developed the mathematical formula and the primary classification method that made the system workable.
• Devised the numerical values assigned to whorl-bearing fingers.

Hem Chandra Bose:

• Another Indian officer who contributed significantly to refining and extending the classification system.
• Worked on sub-classification and telegraphic coding of fingerprints.

Significance:

• The first Fingerprint Bureau in the world was established in Calcutta (1897) based on this work.
• Although the system bears Henry's name, the core intellectual and mathematical contributions came from Haque and Bose, highlighting India's central role in fingerprint science. Their contributions were later formally acknowledged.