INTRODUCTION TO FINGERPRINTS
1.1. Concept and Definition
A fingerprint is the impression of the friction ridge skin present on the palmar surface of fingers,
thumbs, palms, toes, or soles of a human being.
These impressions are formed due to sweat, oils, and other secretions released by sweat glands
located beneath the epidermis. When a person touches a surface, a pattern of these ridges and
furrows is transferred to that surface in the form of a fingerprint.
A fingerprint is an impression of the friction ridge skin of a human finger, made when the finger
encounters a surface, either accidentally or deliberately.
1.2. Formation of Fingerprints
Fingerprints are formed during fetal development (around the 10th week of gestation) and
remain unchanged throughout life except for injuries that destroy the dermal layer.
They consist of raised ridges and depressed furrows, which form unique patterns.
These ridges contain sweat pores that excrete moisture (perspiration) made up of:
• Water (~99%)
• Organic substances (~1%) such as:
o Amino acids
, o Urea
o Fats and oils
o Sugars
• Inorganic substances including:
o Sodium
o Potassium
o Calcium
o Magnesium
o Chlorides and sulfates
These secretions, when transferred to a surface, can leave behind a visible or invisible
impression depending on the type of surface and residue.
1.3. Nature and Composition of Fingerprints
When the fingertip touches any surface, microscopic deposits of perspiration and oil adhere
to the substrate.
This composition helps in chemical development of latent prints since various reagents react
with:
• Amino acids (e.g., ninhydrin)
• Chlorides (e.g., silver nitrate)
• Oils/fats (e.g., iodine fumes)
Thus, even invisible prints can be revealed and made visible using proper development
techniques.
1.4. Fingerprints as Forensic Evidence
Fingerprints are considered one of the most reliable forms of physical evidence because of
the following properties:
A. Uniqueness
No two individuals, including identical twins, have the same fingerprint pattern.
, B. Permanence
Fingerprints remain unchanged throughout life — they neither alter with age nor
environment.
C. Universality
Every individual has fingerprints, making them universally applicable for identification.
D. Classifiability
Fingerprints can be categorized into basic pattern types (arches, loops, whorls) and
minutiae, allowing systematic comparison.
1.5. Fingerprints as Chance Prints
At a crime scene, fingerprints are often left unknowingly by the perpetrator. Such prints are
referred to as chance prints — since they are deposited “by chance” during contact with
surfaces or objects.
Chance prints can be:
1.1. Concept and Definition
A fingerprint is the impression of the friction ridge skin present on the palmar surface of fingers,
thumbs, palms, toes, or soles of a human being.
These impressions are formed due to sweat, oils, and other secretions released by sweat glands
located beneath the epidermis. When a person touches a surface, a pattern of these ridges and
furrows is transferred to that surface in the form of a fingerprint.
A fingerprint is an impression of the friction ridge skin of a human finger, made when the finger
encounters a surface, either accidentally or deliberately.
1.2. Formation of Fingerprints
Fingerprints are formed during fetal development (around the 10th week of gestation) and
remain unchanged throughout life except for injuries that destroy the dermal layer.
They consist of raised ridges and depressed furrows, which form unique patterns.
These ridges contain sweat pores that excrete moisture (perspiration) made up of:
• Water (~99%)
• Organic substances (~1%) such as:
o Amino acids
, o Urea
o Fats and oils
o Sugars
• Inorganic substances including:
o Sodium
o Potassium
o Calcium
o Magnesium
o Chlorides and sulfates
These secretions, when transferred to a surface, can leave behind a visible or invisible
impression depending on the type of surface and residue.
1.3. Nature and Composition of Fingerprints
When the fingertip touches any surface, microscopic deposits of perspiration and oil adhere
to the substrate.
This composition helps in chemical development of latent prints since various reagents react
with:
• Amino acids (e.g., ninhydrin)
• Chlorides (e.g., silver nitrate)
• Oils/fats (e.g., iodine fumes)
Thus, even invisible prints can be revealed and made visible using proper development
techniques.
1.4. Fingerprints as Forensic Evidence
Fingerprints are considered one of the most reliable forms of physical evidence because of
the following properties:
A. Uniqueness
No two individuals, including identical twins, have the same fingerprint pattern.
, B. Permanence
Fingerprints remain unchanged throughout life — they neither alter with age nor
environment.
C. Universality
Every individual has fingerprints, making them universally applicable for identification.
D. Classifiability
Fingerprints can be categorized into basic pattern types (arches, loops, whorls) and
minutiae, allowing systematic comparison.
1.5. Fingerprints as Chance Prints
At a crime scene, fingerprints are often left unknowingly by the perpetrator. Such prints are
referred to as chance prints — since they are deposited “by chance” during contact with
surfaces or objects.
Chance prints can be:
