Investigating the Future: Day 6 of International Forensic Science Week - FINGERPRINT

Why Are Fingerprints Important?

1. Unique: No two individuals (even identical twins) have the same fingerprints.

2. Permanent: Fingerprints do not change throughout a person’s life.

3. Classifiable: Fingerprints can be systematically recorded and stored.

4. Easily Left Behind: They can be found on many surfaces — glass, metal, paper, skin, etc.

History and Development of Fingerprint

One of the earliest and most trustworthy ways to identify someone is through their fingerprints.  From its ancient use for seals and signatures to its current use as a scientific and legal instrument in contemporary forensic investigations, its history spans thousands of years.

The father of fingerprint examination is Sir Francis Galton (1822–1911).

Why Sir Francis Galton?

• He was the first to scientifically study and classify fingerprint patterns.

• Published the landmark book “Finger Prints” (1892), which:

  • Established the uniqueness and permanence of fingerprints.

  • Introduced the basic classification system still used today.

• He laid the scientific foundation for using fingerprints in personal identification and forensic investigations.

Other Important Pioneers

• Sir William Herschel: First to use fingerprints for identity verification in India (mid-1800s).

• Henry Faulds: Early advocate for fingerprint use in criminal investigations.

• Sir Edward Henry: Developed the Henry Classification System used worldwide for filing fingerprints.

Fundamental Principles of Fingerprint Identification

Fingerprint identification is based on scientific principles that make fingerprints a reliable and legally accepted method of personal identification in forensic science.

There are four fundamental principles that form the foundation of fingerprint science

1. Principle of Uniqueness

• Definition: No two individuals have identical fingerprints — not even identical twins.

• Reason: The ridge patterns (minutiae points) and their arrangement are genetically influenced but formed by random pressure and movement in the womb.

• Forensic Value: Allows absolute individualization of a person based on fingerprint evidence.

Example: Even if two people have the same fingerprint pattern type (e.g., loop), the minutiae arrangement (ridge endings, bifurcations, islands) will differ.

2. Principle of Permanence (Permanency)

• Definition: Fingerprint patterns remain unchanged throughout a person's life.

• Formed: In the fetal stage (around 10–16 weeks of gestation).

• Destroyed only by: Deep injury damaging the dermal papillae (e.g., burns, cuts, surgery).

• Forensic Value: Fingerprints can be used to identify living or deceased persons regardless of age.

Note: Even if the skin peels off, the new skin regenerates with the same pattern.

3. Principle of Comparison (Minutiae/Individual Characteristics)

• Definition: Individual identification is based on the comparison of ridge characteristics (called minutiae points) such as:

  • Ridge endings

  • Bifurcations

  • Enclosures

  • Dots or islands

  • Short ridges

• Minimum Matching Points: Many countries require a minimum number of matching minutiae (India typically uses 8 to 12+).

• Forensic Value: This principle allows one-to-one matching and is crucial for establishing identity in court.

Types of Fingerprints (in Forensic Science)

Fingerprints can be classified based on pattern and appearance at the crime scene. These classifications are important for identification, comparison, and investigative use.

I. Based on Pattern – (Class Characteristics)

There are 3 major classes of fingerprint patterns, further divided into subtypes:

1. Loop (Most common – ~60–65% of people)

• Ridge lines enter from one side, curve, and exit from the same side.

• Contains one delta and a core.

• Types:

  • Ulnar loop: Opens towards the little finger.

  • Radial loop: Opens towards the thumb.

  • Ulnar and radial loops are named based on the bone on the corresponding side of the forearm.

2. Whorl (~30–35%)

• Ridges form circular or spiral patterns.

• Contains two deltas.

• Types:

  • Plain Whorl

  • Central Pocket Loop Whorl

  • Double Loop Whorl

  • Accidental Whorl

  • A whorl must have at least one ridge making a complete circuit.

3. Arch (Least common – ~5–10%)

• Ridges enter from one side and exit the other, no delta or core.

• Types:

  • Plain Arch: Smooth rise in the center.

  • Tented Arch: Sharp upthrust or spike in the center.

  • Arches are the simplest and rarest patterns.

II. Based on Visibility at Scene – (Crime Scene Classification)

1. Latent Fingerprints

• Invisible to the naked eye.

• Formed by sweat, oil, and other body secretions.

• Detected using:

  • Powder dusting

  • Ninhydrin

  • Cyanoacrylate (superglue) fuming

  • UV or laser light

2. Patent Fingerprints

• Visible prints.

• Made by blood, ink, paint, dirt, or grease.

• Directly seen on surfaces like glass, paper, or walls.

3. Plastic Fingerprints

• 3D impressions left in soft materials like

  • Wax

  • Soap

  • Butter

  • Wet paint

• Can be photographed or cast using plaster.

Fingerprint Characteristics (Minutiae Points)

Fingerprint characteristics, also called minutiae, are the tiny details in the ridge patterns that make each fingerprint unique. These are the basis for individual identification in forensic science.

Common Types of Fingerprint Characteristics