Upload
ferdinand-abner-underwood
View
223
Download
1
Tags:
Embed Size (px)
Citation preview
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.
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.
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.