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Do Now:

1.Name the 5 fiber weave types.2.What two parts of hair could be used to distinguish between ethnicities?3.Describe the proper way to collect hair from a crime scene4.Name the 5 fiber weave types AGAIN.5.A victim was found at12:00pm with a temperature of 22 degrees. How long has this victim been dead? What time did he die?

*If students are talking during Do Now – pop quiz (click here)

Objective:. •SWBAT understand how fibers are compared through physical and

chemical analysis .

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Fibers

‡ determining what an attacker was wearing at the time of the incident.

‡ identify the make of the garment and thus the manufacturer.

‡ Hair and Fiber

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Burn Test

‡ Smoke‡ Smell‡ How the fiber burns‡ Ashes

‡ Database

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‡ Students will identify the various parts of a hair.‡ Students will describe the variations in the structure of the medulla,

cortex and cuticle.‡ Students will distinguish between human and nonhuman animal hair.‡ Students will distinguish between hair between individuals and

ethnicities. ‡ Students will explain how hair can be used in a forensic investigation.‡ Students will identify and describe common weave patterns of textile

samples.‡ Students will understand how fibers are compared various through

physical and chemical analysis.

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‡ http://www.quia.com/rr/396401.html?AP_rand=821513298&playHTML=1‡  ‡ http://www.superteachertools.com/jeopardy/usergames/Mar201211/

game1331565192.php‡ http://www.superteachertools.com/jeopardy/usergames/Sep201339/

game1331565192.php

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Exit Ticket

‡ Name the 3 layers of hair‡ Name the function of each layer‡ How can hair and fiber be useful in an investigation ‡ What is a burn test‡ How can the medulla be used to narrow down the

suspects.

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Human Medulla

Human medulla may be continuous, fragmented, or absent.

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Medullary Index

Determined by measuring the diameter of the medulla and dividing it by the diameter of the hair.

Medullary index for human hair is generally less than 1/3

macrometers

For animal hair, it is usually greater than ½ macrometers

mouse

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Hair Shape and Cross Section

Can be straight, curly, or kinky, depending on the cross-section, which may be round, oval, or crescent-shaped.

Round(Straight)

Oval(Curly)

Crescent moon (Kinky)

Human hair ranges in diameter from 25-125 µm

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Racial Characteristics of Hair‡ Risky, but generally…

‡ Asians & Native Americans – round cross section with no twisting

‡ American & European whites, Mexicans, and people of Middle Eastern background – oval cross section, rarely with a twist or undulation.

‡ African heritage – flat to crescent-shaped cross section with twist, undulation and dense, clumped pigmentation.

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Hair Growth

Grows 1 cm per month; approximately one-half inch per month

Replaced about every 3-5 years with new hair

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The Root

Human roots look different based on whether they have been forcibly removed or they are telogen hairs and have fallen out.

Animal roots vary, but in general have a spear shape.

Fallen out Forcibly removed

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The Tip

Tip of mature hair will taper to a point

Recently cut hair is squared off at the tip, but within 2-3 weeks the tip becomes rounded

Frayed hair tip results from over-processing (bleach, coloring, straighteners, blow dryer) or age

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Hair Comparison

Color

Length

Diameter

Distribution, shape, and color intensity of pigment granules

        

Scale types

Presence or absence of medulla

Medullary type

Medullary pattern

Medullary index• Dyed hair has color in cuticle and cortex

• Bleaching removes pigment and gives a yellow tint

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Exit Ticket

‡ What details can microscopes give about hair characteristics?

‡ Using hair characteristics, name some of the biggest difference between you and your groups.

‡ The three layers of hair are:‡ A. Cuticle, Convex, Concave‡ B Convex, Medulla, Cuticle‡ C. Cuticle, Cortex, Medulla‡ D. Cuticle, Cortex, Mortem

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DNA from Hair

The root contains nuclear DNA. If the hair has been forcibly removed, some follicular tissue containing DNA may be attached.

The hair shaft contains abundant mitochondrial DNA, inherited only from the mother. It can be typed by comparing relatives if no DNA from the body is available. This process is more difficult and more costly than using nuclear DNA.

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Collection of Hair

Questioned hairs must be accompanied by an adequate number of control samples.

• From victim

• From possible suspects

• From others who may have deposited hair at the scene

Control sample

• 50 full-length hairs from all areas of scalp

• 24 full-length pubic hairs

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Hair Toxicology

Advantages:

• Easy to collect and store

• Is externally available

• Can provide information on the individual’s history of drug use or evidence of poisoning

Collections must be taken from different locations on the body to get an accurate timeline.

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Hair as Chemical Indicator

‡ Metabolite – a specific product of a substance, formed by chemical processes in the body

‡ Drugs and their metabolites, vitamins and poisons can be detected with just a few mm of hair.

‡ Provides back up to urine and blood testing‡ Drug metabolites only detectable in urine for

approx. 3-5 days from last use.‡ Hair grows at approx. 1 cm per month and will

record drug use over a longer period of time.

‡ Can establish dietary deficiencies and diseases

‡ Oils on scalp can deposit onto hair and will leave evidence of environment

‡ Smoke from crack cocaine can be deposited this way

‡ May provide a false positive

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Hair Toxicology, continued

Napoleon died in exile in 1821. By analyzing his hair, some investigators suggest he was poisoned by the deliberate administration of arsenic; others suggest that it was vapors from the dyes in the wallpaper that killed him.

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More about Hair

For additional information about hair and other trace evidence, check out truTV’s Crime Library at:

www.crimelibrary.com/criminal_mind/forensics/trace/1.html