WEEK 6

Hair is often encountered as trace physical evidence in various crimes:
- Sex crimes: such as rape, sodomy, and bestiality.
- Murder: hair can be traced at a scene or found on the weapon, suspect, or victim.
- Assault: hair found on the victim, suspect, weapon, or scene.
- Robbery: hair found at the point of entry and exit.
- Theft: hair found on stolen items.
- Car accidents: particularly hit-and-run incidents.
- Poaching: animal hair found on meat.
Forensic hair analysis cannot sufficiently individualise a specific hair to a person via morphology alone, but can provide corroborating evidence.
DNA extraction from hair offers the ability to individualise.
Hair is an attachment of the skin that grows from the hair follicle consisting of a root, shaft, and tip.

When submitting hair to a lab, it must be accompanied by sufficient reference samples:
- Samples from the victim and suspected perpetrators for comparative analysis.
Hair should be collected from the same body part (e.g., head and pubic).
Suggested collection amounts include:
- 50 head hairs.
- Approximately 24 pubic hairs.
Including the root with collected hair is recommended for DNA sampling.
Autopsy procedures should include hair collection as standard procedure, regardless of its immediate necessity.
Failing to collect hair samples from victims may jeopardize legal proceedings if bodies are later cremated or buried.

Hair can be divided into three sections: root, shaft, and tip.
The focus here will be on the hair shaft, especially its components:
- Cuticle
- Cortex
- Medulla

Features enhancing hair's forensic value:
- Resistance to chemical decomposition.
- Retention of structural features over long periods.
The cuticle consists of overlapping scales that point towards the hair tip, created from keratinised cells.
Animal hair patterns can resemble roof tiles, aiding species identification.

The cortex is located beneath the cuticle and contains pigment granules responsible for hair color.
The distribution, shape, and color intensity of these granules are essential for comparing hairs.

The medulla is a central canal-like structure within the hair:
- Its presence and appearance vary significantly among individuals and between species.
- It can be classified as:
- Continuous
- Interrupted
- Fragmented
- Absent
Human hair typically lacks a medulla or has a fragmented form, with an exception for Asian ancestry where continuous medullae may be observed.

The hair root and surrounding follicle cells are essential for hair production and growth:
The three hair growth phases are:
- Anagen phase
- Catagen phase
- Telogen phase

Lasts up to six years; the root remains attached to the follicle, shaped like a flame.
Hairs pulled in this phase often have a follicular tag, which is critical for DNA extraction.
Follicular tag: a translucent piece of tissue containing rich DNA.

Laboratory examinations include:
1. Macroscopic tests: General shape and length of hair.
2. Microscopic examinations: Cross-section and detailed morphology.
3. Chemical analysis: Such as amino acid profiling.
Hair characteristics vary by body part:
- Head hair: typically longest, often soft, may be treated chemically.
- Pubic hair: coarse, exhibits buckling.
- Limb hair: fine, with tapered tips; rounded and worn scale ends.
- Facial hair: coarse, with irregular shapes; may possess double medullae.
- Chest hair: moderate diameter with darkened tips, varying in characteristics.
- Auxiliary hair: resembling pubic hair but less buckled.
- Other body hairs: Eyebrows and eyelashes show stubby features; trunk hair combines limb and pubic traits.

Tests determine color, diameter, and scale appearance.
Disputed and reference hair are analyzed under comparison microscopes:
Key purpose: to distinguish hairs from fibers, determining general characteristics through scale counts.
Scanning Electron Microscopy (SEM) enhances scale examination efficiency.
Differences in dyed versus natural hair can also be detected.

Hair's longevity aids in gathering evidence even post-mortem.
Techniques like atomic absorption can identify metalliferous poisons (e.g., arsenic).
Blood group typing feasible when a follicle adheres to the hair root.

Nuclear DNA can be extracted from hair roots or follicular tissue, especially in the anagen phase,
Mitochondrial DNA (mtDNA) is a secondary option, passed maternally, facilitating familial relationship analysis but not individualisation.
mtDNA presence can narrow down population subsets.

Lab requests primarily involve comparing hairs found at crime scenes to those of suspects.
Key comparison features include:
- Color
- Length
- Diameter
- Medulla presence or absence
- Pigment distribution, shape, and intensity in the cortex
Evaluations can reveal:
- Body origin of hair
- Racial background
- Age and sex determinations
Forcibly removed hairs, stratified by hair structure:
- Root with follicular tissue indicates force.
- Bulbous root suggests natural fall-out.
- Pulling speed affects follicular tissue attachment.

Initial analysis checks if hair is human or animal; microscopic morphology aids in differentiation.
Species identification often possible.

Three general ancestry categories:
- European: Irregular oval cross-section; color range from black to light blond; typical growth rate is approximately 1.2 cm/month.
- Asian: Faster growth rate (1.3 cm/month); circular cross-section; predominantly black; densely granule distribution.
- African: Flat to oval cross-section; grows slowest (0.9 cm/month); usually black; distinctive twisted rod shape and uneven longitudinal twists.