Definition
Hair is a thin, thread-like part of the body made mostly of a strong protein called keratin. It grows out of tiny openings in the skin called follicles. Hair can be found in many shapes and types on all mammals, including people and animals. It grows from the skin and helps with things like keeping the body warm, sensing touch, and even showing identity or style. Hair is one of the special features that all mammals share.
Parts of Hair
- Hair Shaft
The hair shaft is the visible portion of the hair that extends out from the scalp.
Cuticle: This is the outer protective layer of the hair, formed by flat, overlapping cells similar to roof shingles. It shields the inner layers from damage and environmental stress.
Cortex: Found beneath the cuticle, the cortex makes up the bulk of the hair strand. It holds most of the hair’s natural pigment (melanin) and determines the hair’s strength, flexibility, and texture.
Medulla: Located at the very center of the hair shaft, the medulla is a soft, often hollow core that may not be present in all hair types. Its exact function is still under study.
- Hair Root
This is the part of the hair embedded in the skin, essential for hair growth.
Hair Bulb: The enlarged base at the end of the hair root where new hair cells are produced.
Dermal Papilla: A small, cone-shaped structure at the base of the hair bulb that supplies blood and nutrients, supporting hair development.
Matrix: Surrounding the dermal papilla, the matrix is filled with rapidly dividing cells that push upward to form the hair shaft.
- Hair Follicle
The follicle is a tubular structure in the skin that encases the hair root and supports its growth.
Sebaceous Gland: Connected to the follicle, this gland releases natural oils (sebum) that moisturize the scalp and soften the hair.
Arrector Pili Muscle: A tiny muscle attached to the follicle that can contract, causing the hair to stand up a reaction often triggered by cold or fear, known as goosebumps.
Types of Hair
- Lanugo – The First Layer of Hair
Definition: Very fine, soft, and usually colorless hair.
Appears: Grows on unborn babies during pregnancy and typically sheds before or just after birth.
Main Role: Acts as a gentle covering to protect fetal skin in the womb.
- Vellus – The Invisible Coat
Definition: Light, short hair that’s barely visible.
Body Locations: Found on most of the body, except on areas like the palms and soles.
Primary Function: Provides slight insulation and shields the skin.
- Terminal – The Fully Grown Hair
Definition: Thick, dark, and longer hair that appears after puberty.
Growth Areas: Seen on the scalp, eyebrows, eyelashes, armpits, beard, chest, and pubic region.
Purpose: Offers protection, helps regulate temperature, and plays a role in appearance and communication.
Hair Types Found in the Animal Kingdom
- Guard Hairs – The Outer Armor
Definition: The rough, visible layer of fur.
Function: Protects against the environment and defines the animal’s coat color and pattern.
- Underfur – The Hidden Warmth
Definition: Soft, fluffy hair beneath the guard layer.
Function: Traps body heat and keeps the animal warm.
- Whiskers – Nature’s Sensors
Definition: Thick, stiff hairs near the face (often around the nose or mouth).
Function: Detects movements, objects, and changes in surroundings – especially useful in the dark.
- Spines and Quills – Built-In Protection
Definition: Strong, pointed hairs that have evolved into natural defense tools.
Function: Acts as a physical barrier against predators, offering safety to the animal.
Based on the structure
- Straight Hair (Type 1)
This hair type grows directly from the scalp without any natural bends or curves. Its strands are cylindrical in shape, giving it a sleek, flat look.
- Wavy Hair (Type 2)
Characterized by soft bends along the length, wavy hair typically forms a loose “S” shape. The strands are slightly oval, giving it a natural bounce without tight curls.
- Curly Hair (Type 3)
Curly hair grows in rounded spirals or loops. The strands have a more compressed oval shape, which causes them to twist as they grow, creating well-defined curls.
- Coily or Kinky Hair (Type 4)
This texture features very tight, compact curls or zigzag shapes. The strands are highly flattened and tend to grow close to the scalp, often appearing thick and dense.
Collection, Packaging & Preserving
- Collecting Hair as Evidence
At the Scene:
Investigators look carefully for hair on items like clothes, bedding, furniture, floors, or weapons. Since hair can be tiny and hard to see, they use special tools to find and pick it up.
Tools Commonly Used:
Tweezers or forceps – to gently pick up visible hairs without damaging them.
Tape strips – sticky tape helps lift small hairs from surfaces.
Vacuum devices – with filters, used to collect hair from large areas.
From Individuals:
Pulled hairs (with the root attached) are taken from suspects or victims when DNA testing is needed.
Combed or brushed hairs are gathered to compare hair types or match with found samples.
- Packaging Hair Evidence
To keep each hair sample clean and separate, it’s packed individually.
Materials Used:
Paper folds (bindles) – small folded papers used to hold the hair.
Envelopes or paper bags – these go around the bindle to give extra protection.
Labels – each sample must be clearly labeled with details like the case number, location, date, and who collected it.
Avoid plastic bags – they can trap moisture, which might damage the hair.
- Preserving Hair Evidence
Once collected, hair must be stored properly so it stays in good condition for testing.
Key Guidelines:
Keep in a cool, dry place, away from sunlight and moisture.
Handle gently to avoid losing any small particles attached to the hair, like skin or oil.
If DNA testing is needed, especially from the hair root, use clean gloves and tools to avoid contamination.
For long-term storage, place hair in high-quality paper containers and keep it in a controlled environment.
Forensic Examination of Hair
Hair can provide important clues in forensic investigations. Experts examine it in several ways to understand its source, condition, and possible connection to a crime.
- Visual Examination
This is the first and most basic step. The hair is observed without any special tools.
Observations include:
- Color
- Length and texture (straight, wavy, curly)
- Signs of treatment or visible damage
- Helps determine if the hair is suitable for further testing.
- Physical Examination
Focuses on the structure and outer features of the hair.
Features studied:
- Thickness
- Medulla pattern (the core of the hair)
- Type of root (pulled or naturally shed)
- Condition of the tips (cut or broken)
- Used to compare hairs from different sources.
- Chemical Examination
- Tests are done to find substances that the hair has been exposed to.
- May reveal:
- Traces of drugs, toxins, or alcohol
- Hair dyes, bleaches, or chemical treatments
- Useful in toxicology or confirming attempts to alter appearance.
- Optical Examination
Microscopes and light techniques are used to study tiny details.
Focus areas:
- Inner hair structure using light passing through the strand
- Surface texture using light reflected off the hair
- Shows fine features not visible to the eye.
- Instrumental Examination
Involves advanced tools and lab equipment for deeper analysis.
Techniques include:
- Comparison microscopes for side-by-side matching
- Electron microscopes for detailed surface images
- Infrared spectroscopy to study chemical composition
- DNA analysis if the root is attached
- Provides precise and high-level data for forensic identification.
Questions and Answers
What is hair mostly made of?
Ans: Hair is built from a strong protein called keratin, which also forms nails.
Where does hair grow from in the skin?
Ans: It grows out of tiny holes in the skin called hair follicles.
Is hair individual or group evidence?
Ans: If the root is missing, it’s usually group (class) evidence. With the root, it can give individual’s DNA.
What are the three parts of a hair strand?
Ans: The outer part is the cuticle, the middle is the cortex, and the center is the medulla.
What is the role of the medulla?
Ans: It’s the central core of the hair and can help tell hairs apart during comparisons.
What is lanugo hair?
Ans: It’s the soft, colorless hair that grows on unborn babies and falls off before or shortly after birth.
What is vellus hair?
Ans: This is the thin, fine hair covering most of the body except certain areas like palms and soles.
What is terminal hair?
Ans: It’s thick, dark hair found on the scalp, underarms, and other areas after puberty.
How is hair shaped based on its texture?
Ans: It may be straight, wavy, curly, or tightly coiled depending on the follicle shape.
What decides how hair feels or looks?
Ans: The natural shape of the hair follicle controls how curly or straight it is.
How do investigators find hair at a scene?
Ans: They search carefully and use tools like tweezers, tape, or vacuums to collect it.
Can hair be taken from people during an investigation?
Ans: Yes, by combing, brushing, or gently pulling it out.
Why is it better to collect hair with the root?
Ans: The root may contain DNA, which helps identify the person it came from.
What’s the first step in handling hair at a scene?
Ans: Spotting and picking up any visible hair from surfaces or objects.
Can hair samples get mixed up or ruined?
Ans: Yes, if they’re not packed or labeled properly.
How should each hair sample be stored?
Ans: Each one must be kept separate, usually in folded paper and then in a labeled envelope.
Why don’t we use plastic bags for hair?
Ans: Because they can hold moisture, which can damage the sample over time.
What should labels on evidence include?
Ans: Things like case ID, date, location, and the person who collected it.
Where should hair be kept after collection?
Ans: In a dry, cool area, away from sunlight or dampness.
Does hair break down over time?
Ans: Yes, especially if not stored in the right conditions.
What is visual hair examination?
Ans: It’s the basic process of looking at the hair’s color, shape, and length with the naked eye.
What does physical hair examination involve?
Ans: It looks at the hair’s size, root, tip, and structure under closer inspection.
What can chemical tests on hair show?
Ans: Whether someone used drugs, poison, or hair products like bleach or dye.
What is optical analysis of hair?
Ans: It uses light-based microscopes to view fine details inside or on the hair.
What is instrumental hair testing?
Ans: It includes using high-tech lab equipment for deep analysis or DNA testing.
Can hair identify a person?
Ans: Yes, but only if the root is attached and contains usable DNA.
What can mitochondrial DNA in hair tell us?
Ans: It links the hair to someone from the same maternal line.
Is colored or treated hair useful in a case?
Ans: Yes, it may show attempts to hide identity or recent changes.
Can animal hairs be part of evidence?
Ans: Absolutely they can link someone to a pet or place.
Why is hair good trace evidence?
Ans: It sticks easily to clothes and objects and can last for a long time.