Hair AnalysisForensic Science

Lawndale

Hair Analysis:

• Hairs are one example of trace evidence which can be examined under the microscope.

• Unfortunately, hair is not the best type of physical evidence for establishing identity.

Hair Analysis (Cont)

• It is impossible to show with any certainty that two hairs came from the same person.

• Hair can be used to rule out certain suspects or scenarios.

• It can be used to support other physical evidence if it is consistent with the rest of the evidence

Hairs can be grouped in 2 ways:

• Racial origin• Body location

Hair examiners can often conclusively eliminate a person as a source of a hair, but rarely can an examiner absolutely associate a hair sample to a given individual.

How is hair analyzed?

Two ways:• Visual Observation- simplest

method of identification done with the naked eye, indicate color, length, and amount of curl.

• Microscopic Examination-Reveals characteristics of its physical structure.

Quiz- Get out a piece of binder paper• 1. T/F- Hair is evidence that can always

link a suspect to a crime scene.• 2. Identify 2 ways scientists can

examine hair.• 3. Identify the two ways hairs can be

grouped. • 4. Describe one way scientists can use

hair as evidence. • 5. The three principle parts of hairs are

---

Structure of HairHair is composed of three principle parts:(Similar to graphite pencil)

• Medulla – • Cortex -• Cuticle –

Medulla

• Central Core, which may be absent• Appears dark when the exhibit is

mounted in a liquid (via a microscope)– May not be visible

• May vary in thickness and continuity (one continuous structure or broken in pieces).

Cortex

• Middle layer of the hair shaft• Provides strength• Makes up most of the mass of hair• Contains microscopic features such

as:pigment, color, size, and distribution.

Cuticle

• Outer coating composed of overlapping scales

• Most important detail in determining from which individual a human hair may have come.

Cuticle• Scales of the cuticle can be

different shapes and textures • Thickness may vary as well

Biology of Hair

•Hair is an outgrowth of the skin and is produced from a structure called the hair follicle.

•Hair is made of the same thing as your fingernails called keratin

Hair Color

Hair color is the result of 2 main pigments – chemical compounds which reflect certain wavelengths of visual light.

• Eumelanin – gives color to brown or black hair

• Pheomelanin – produces the color in blonde or red hair.

Get out a sheet of binder paper

Hair Shape and texture• Shape – round, crescent or oval

cross- section• Texture – curly, wavy, straight, kinky

Both are influenced heavily by genes!!!!

However, nutritional status and intentional alteration (heat, curling, coloring) can affect the physical appearance of hair.

Good Vs Damaged Hair