1. Turn in Ch. 10 foldable if you have not already done so.

2. Take out your notebook and complete the bellringer.

Bellringer:• Describe Locard’s Exchange Principle.• Is hair found at a crime scene classified as

individual evidence? Why or why not?

Forensic Science

http://media.popularmechanics.com/images/PMX0706FORENSICSHairSmall.jpg Presentation developed by T. Trimpe 2006 http://sciencespot.net/

• Class evidence

• Removal typically indicates physical contact between victim and perpetrator (Think Locard’s exchange principle)

• Strong evidence to place individual at crime scene

• Compare hairs by color and structure

• Extract DNA from root for comparison

• Appendage of the skin• Grows out of the hair

follicle• Length of hair extends

from follicle shaft tip

• Follicle (root) contains DNA

• Regulate body temperature (insulation)

• Decrease friction

• Protect against sunlight

• Sense organ

• Three layers:– Cuticle: surface of hair

– Cortex: main body, contains pigment

– Medulla: hollow core

Hair Structure

Hair is composed of three principal parts:

The structure of hair has been compared to that of a pencil with the medulla being the lead, the cortex being the wood and the cuticle being the paint on the outside.

http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair

Cuticle – outer coating composed of overlapping scales

Cortex – protein-rich structure around the medulla that contains pigment

Medulla – central core(may be absent)

Today’s Assignment

• Complete your graphic organizer on hair structure

• It is recommended that you include pictures

• Colored pencils are available up front if you need them – please make sure to return them neatly and in the correct space or Mr. Alper will be =(

Characteristics of the cuticle may be important in distinguishing between hairs of different species but are often not useful in distinguishing between different people.

Info: http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair Image: http://www.hairdressersus.com/micro/Image5b.jpg

Hair Structure

CuticleThe cuticle varies in:

• Its scales, How many there are per centimeter, How much they overlap, Their overall shape, and How much they protrude from the surface

• Its thickness, and • Whether or not it contains pigment.

Cortex

The cortex varies in:• Thickness• Texture• Color

•This is where pigment granules are deposited

• 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 root and tip.

Info: http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair Image: http://www.extrapersonality.com/hair.html

Hair Structure

MedullaThe medulla may vary in:

• Thickness• Continuity - one continuous structure or broken into pieces• Opacity - how much light is able to pass through it

• It may also be absent in some species.

http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair

Like the cuticle, the medulla can be important for distinguishing between hairs of different species, but often does not lend much important information to the differentiation between hairs from different people.

Hair Structure

http://www.bfro.net/images/whatis/figures/Fig.%203%20with%20caption.jpg

The Root

Human hairs go through 3 stages of growth:• Anagen phase

• Initial growth phase where the follicle actively produces hair

• Root has a flame-like shape• Catagen phase

• Transition stage bet. Anagen and catagen phases• Root takes on an elongated shape

• Telogen phase• Final growth stage in which hair naturally falls out• Root almost non-existent

http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair

Hair Structure

http://www.bfro.net/images/whatis/figures/Fig.%203%20with%20caption.jpg

2 Main Goals: 1. Match hair found @ crime scene w/ hair found on

suspect2. ID the species of origin

http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair

Hair Identification and Comparison

http://www.bfro.net/images/whatis/figures/Fig.%203%20with%20caption.jpg

Distinguishing among animals tends to be much easier than among humans:•Focus is placed on color, length, and diameter of hairs

• Additionally, the presence or absence of the medulla, distinct shape of hair, the color intensity of pigment in the cortex

• If color is present in the cuticle as well as the cortex, the hair was most likely dyed

• If there is no trace of pigment but the hair has a yellowish tint, it was most likely bleached

Directions:

Your team will need to use a microscope to document all the hairs and in your set.

Write the name of the hair on the line and then draw what you see under medium or high power. Be sure to indicate the power of magnification!

Add a description that highlights the unique characteristics of each hair sample.

Pay attention to details to help you identify samples during the Hair Challenge activity.

Hair Identification Lab