Hair Analysis Forensic Science Lawndale Hair Analysis Hairs

Hair Analysis Forensic 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 Hair 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 crosssection • 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