Forensic Science Lesson 08: Hair Evidence Part 1-Hair Anatomy

The Study of Hair

Lesson Objectives

• Identify the Various Parts of Hair

• Describe Variations in Hair Part Structures

Case Study: Eva Shoen

• 1990, Telluride Colorado Eva Shoen was found murdered via gunshot to the head

  • The bullet could not be matched to a known gun

• 3 years later, someone called in accusing their brother

  • He had a gun, but it was damaged and couldn't be matched to the bullet

• Police learned he was in the area of the murder, and seen disposing two bundles in the desert

• They found the bundles on the side of the road and found strands matching Eva's Hair in them

• He confessed when told about the hair evidence

Introduction: Hair as Evidence

• Overall, Hair is considered Class Evidence

  • Without the Follicle, it can not be used to identify a person

  • Hair can be very similar among individuals

Introduction: Why look at Hair as Evidence?

• Is transferred easily

  • Secondary Transfer: Evidence that is transferred by a source other than the original

• Does not decompose easily, and can last a long time

  • Can take 1-2 years to begin to break down

  • Holds Chemicals inside of it, and can tell about poisoning, drug use, and nutrition

History of Hair Analysis

• First recognized as important evidence in the 1800's

• Two writings helped explain hair as forensic evidence

  • 1883: The Principles and Practice of Medical Jurisprudence by Taylor and Stevenson

    • Showed pictures of hair under a microscope and defined parts of a hair

  • 1910: Le Poil de l’Homme et des Animaux by Balthazar and Lambert

    • Showed the differences between human and animal hairs

History of Hair Analysis

• 1934: A comparison microscope was first used for hair analysis

  • Allowed for two samples to be placed side by side

• Modern Developments:

  • DNA Fingerprinting from a hair follicle

  • Neutron activation Analysis

The Function of Hair

• Hair is a trait of all mammals

• Primary Function: Insulation and Warmth

  • Traps warm air close the skin

• Other uses

  • Decreases friction from outside forces

  • Protect Skin

  • Act as a sense organ

• In Most non-human mammals it is called fur

Human Hair

• Hair acts as less of an insulator for humans because we have less hair

• When born, we have approximately 5 million hair follicles

  • Only 2% of those are on the head

  • All formed in Utero at 5 months

• As we age, our hair becomes less dense

Multiple Choice

True or False: Hair is one of the first body parts to decompose after death

• True

• False

Multiple Choice

Overall, Hair is considered to be which type of evidence

• Class

• Individual

• Useless

• Direct

Multiple Select

Select all of the functions of hair in mammals

• Help control body temperature

• Protect the Skin

• Decrease friction from outside forces

• Act as a sensory organ

• Absorb body odor when stressed

Multiple Choice

True or False: Hair can help indicate if someone has been poisoned

• True

• False

The Structure of Hair

• Each Hair has two parts

  • Follicle

  • Shaft

Hair Follicle and its Parts

• Hair Follicle: The actively growing root or base of a hair containing Nuclear DNA and Living Cells

  • Papilla: a network of blood vessels at the end of a hair Follicle

    • Provide nutrients to the hair to help it grow

  • Sebaceous Gland: secretes oil to lubricate and condition the hair as it grows

  • Hair Erector Muscle: pulls the hair and causes it to stand up when stimulated by the environment

Hair Shaft

• Hair Shaft: The part of the hair that extends past the skin

  • Made up of the protein Keratin

    • Strong and flexible chain of amino acids that form a spiral

  • Does not contain Nuclear DNA, but has Mitochondiral DNA

  • Has three layers

    • Medulla: Innermost

    • Cortex: Middle layer

    • Outer Cuticle: Outside

Why does the type of DNA matter?

• Each person has two different types of DNA in their body

  • Nuclear DNA: DNA that is unique to a person

    • Can be traced and matched to one individual

  • Mitochondrial DNA: A fragment of DNA found in the mitochondria of cells

    • Passed from mother to offspring

    • Can be traced and matched to many individuals along maternal lines

Cuticle

• The transparent outer layer of the hair shaft

• Made up of overlapping scales

  • are flat and described as imbricate in humans

  • Point away from the scalp towards the outside world

• Damage to the cuticle can indicate some sort of chemical presence

Cortex

• The largest part of the hair shaft

• Contains the melanin in hair

  • Melanin Granules: bits of pigment found in the cortex of the hair

    • Can vary in size, and if large enough can be seen under a micrscope

Medulla

• The center of a hair shaft

• Can be hollow or filled

• Not always able to be seen clearly

• Five different types of Medulla

Medulla

Multiple Choice

Name the outer layer of the hair

• Cortex

• Medulla

• Cuticle

• Root Sheath

Multiple Choice

Which Letter is the Hair Erector Muscle

• A

• B

• E

• C

• D

Multiple Choice

Which Part of the hair is A?

• Cuticle

• Hair Follicle

• Cortex

• Medulla

Multiple Choice

The Hair Shaft is the....

• Part of the hair that is visible on the scalp or skin.

• Part of hair that is enclosed in the hair follicle

• "Bag" that encloses the root of hair

• structure containing capillaries and nerves that supplies nutrients to the hair

Multiple Choice

Which Part of the Hair is B?

• Cuticle

• Hair Follicle

• medulla

• Cortex

Multiple Choice

Is the DNA found in a hair shaft an example of individual or class evidence?

• Individual

• Class

Multiple Choice

Which Part of the Hair is C?

• Hair Erector Muscle

• sweat gland

• sebaceous (oil) gland

• hair follicle