1. Hairs & Fibers Forensic Science
Presentation developed by T. Trimpe

2. Biology of Hair
Hair is composed of the protein __________, which is also the primary component of finger and toe nails.
Hair is produced from a structure called the hair ________. Humans develop hair follicles during fetal development, and no new ___________ are produced after birth.
Hair color is mostly the result of _____________, which are chemical compounds that reflect certain wavelengths of visible light.
Hair _________ (round or oval) and _________ (curly or straight) is influenced heavily by genes.
The body area (head, arm, leg, back, etc.) from which a hair originated can be determined by the sample’s _____,_____,_____,_____, and other physical characteristics.
In order to test hair evidence for DNA, the ________ must be present.
Sources: &

3. Hair Structure Hair is composed of three principal parts:
______– outer coating composed of overlapping scales
______– protein-rich ;contains pigment
________– central core (may be absent)
The structure of hair has been compared to that of a pencil with the medulla being the ______, the cortex being the _____ and the cuticle being the _______ on the outside.

4. Hair Structure Cuticle The cuticle varies in: Its ____________
Characteristics of the cuticle may be important in distinguishing between hairs of different ______ but are often not useful in distinguishing between different __________.
Info: Image:

5. Hair Structure Cortex The cortex varies in: _________ ________
__________
Distribution of the cortex is perhaps the most important component in determining from which individual a human hair may have come.
Microscopic examination can also reveal the condition and shape of the ______ and _______.
Info: Image:

6. Hair Structure Medulla The medulla may vary in: ___________
___________ - one continuous structure or broken into pieces
It may also be _________ in some species.
Like the cuticle, the medulla can be important for distinguishing between hairs of different _______, but often does not lend much important information to the differentiation between hairs from different _____.

7. Can you identify the animal hairs shown?B C D G E F H I
Teacher Note: I challenge students to identify each hair sample pictured on this slide as they examine the sets of animal hairs I have prepared for them. An observation worksheet is available on my website which requires students to draw an image of what they see and add a description that highlights unique characteristics of each specimen. A key for the animal hairs is available on the next to last slide of this presentation!
Think About It …
In which samples are we viewing the cuticle? How do they compare?
(2) In which samples are we viewing the medulla? How do they compare?
(3) What characteristics can be used to identify hair samples?

8. Types of Animal Hairs - Key
Cat
Horse
Pig
Human A B C D G E F H I
Deer
Dog
Rabbit
Rat
Human