Forensic Science Lesson 10: Hair Evidence Part 3

Hair Evidence Part 3

The Death of Napoleon Bonaparte is considered to be controversial, with some historians claiming foul play was involved. To this day, Scientists continue to check the remains of his hair for signs of poisoning, with inconsistent results.

Multiple Choice

Which hair growth phase comes last?

• Telogen Phase

• Catagen Phase

• Anagen Phase

Multiple Choice

Which type of hair has a double medulla?

• Head hair

• Eyebrows/Eyelashes

• Beard

• Pubic

• Armpit

Multiple Choice

During which stage of the hairs lifespan is it not growing?

• Catagen

• Anangen

• Telogen

Multiple Choice

This hair structure is broken down into three parts; Cuticle, Cortex, & Medulla.

• Hair Bulb

• Hair Root

• Hair Follicle

• Hair Shaft

Multiple Choice

What does the arrector pili muscle do?

• Push sweat out

• Thermoregulation

• Make hair stick up

• Waterproofing

Lesson Objectives

• Discuss the racial determination of hair

• Discuss the difference between human and animal hair

• Discuss how hair is studied in a forensic Investigation

Racial Differences in Hair

• Hair examiners have created three different categories of hair, based on differences between races

  • These are generalized categories, and not 100% fact for every person of each "race"

  • As populations mix, these categories become more and more mixed as well

European Hair

• Tends to be overall straight with a slight wave to wavey

• Has small pigment granules distributed evenly with spaces between them

• Has an oval diameter with little to no variation

• Shows the largest range in hair color

Asian Hair

• Tends to be the straightest type of hair

• Has a course texture

• Has a thick Cuticle and continuous medulla

• Very Densely distributed pigment granules

• Cross section is circular with a wide diameter

African Hair

• Has a curly or coiled appearance

• Pigment Granules are densely distributed in clumps

  • May vary in size or shape within a hair

• Cross section is much Flatter than other hair types

Multiple Choice

True or False: All Hair falls distinctly into one of the three race categories

• True

• False

Multiple Choice

Which type of hair is categorized by being wavy and showing a wide range of color?

• European

• Asian

• African

• All Hair types

• None of the Hair types

Multiple Choice

Which Hair category is coiled with a flat cross-section?

• African

• European

• Asian

• All Hair Types

• None of the Hair types

Multiple Choice

Which Hair Category has a circular diameter?

• African

• Asian

• European

• None of the hair types

• All Hair Types

Multiple Choice

Which Hair Category Carries Nuclear DNA in the Shaft?

• African

• Asian

• European

• None of the hair types

• All Hair Types

Differences in Animal Hair-Pigmentation

• The Pattern of Pigmentation

  • Humans have more pigment toward the cuticle

  • Animals have more pigment toward the medulla

  • Human hair has one color all along the shaft, while animal hair can change color in bands

  • Ovid Bodies: A repeating pattern of rounded pigment

Differences in Animal Hair-Medula

• The Medullary Index: The ratio of the diameter of the medulla to the diameter of the entire hair

  • In animals: is greater than 0.5

  • In Humans is 0.33 or less

  • Between 0.33 and 0.5 it is hard to tell

• The medulla is always continuous

Differences in Animal Hair-Cuitcle

• The Cuticle is different between animals in humans

• Humans have flat imbricate cuticles

• Rodents and bats have coronal cuticles: Look like a crown

• Cats, seals, and minks have Spinous Cuticles: that look like petals

• Dog scales are too small to see clearly without a high powered microscope

Multiple Choice

What is the repeated pattern of rounded pigments in animal hair?

• Ovid Bodies

• Cortex Spots

• Pigment Bodies

• Colored Spots

Multiple Choice

Which type of Hair has the largest Medullary Index?

• Animal Hair

• Asian Hair

• African Hair

• European Hair

Dropdown

Humans have more pigment toward the ​

Select answer

, while animals have more pigment toward the ​

Select answer

How Hair is Used in Investigations

• After hair is collected, it is first looked at under a low powered microscope to determine if they are human or animal

• Is studied both macroscopically and microscopically

  • Macroscopic Traits: can be seen without a microscope

    • Color

    • Length

    • Curliness

  • Microscopic Traits between (40x and 400x)

    • Medulla pattern

    • Cortex pigment

    • Cuticle Scales

How Hair is Used in Investigations

• Phase Contrast Microscopy: uses a special lens that focuses light through objects of different refractive indexes

  • Show more detail

  • Can have different settings to show different details

How Hair is Used in Investigations

• Fluorescence Microscope: Shines colored beams of light through an object to cause certain chemicals reemit light of a different color

  • Helps indicate the presence of dye

Testing for Chemicals in Hair

• Chemicals that are absorbed in the skin can be incorporated in hair as it grows

  • Only a few millimeters are needed

• Is used to back up blood and Urine tests because the chemicals remain longer

• Can be tested for Heavy Metals

  • The hair is dissolved to release any possible chemicals for analysis by a chemist

Testing for Chemicals in Hair-False Positives

• False Positive: A test result that indicates something that may not be true

• Oils in the hair can absorb chemicals from the environment

  • A person may not have ingested poison, but it may show up in their hair

Testing for Chemicals in Hair

• We can use the same conversions for hair growth and dyeing for poisoning

  • Poison does not spread in the shaft, and is only located in the areas growing when exposed

• Example: A person is brought to the hospital with symptoms resembling chronic arsenic poisoning. When studying the hair shaft, they found that the toxin first appears 1.3 cm away from the root. How many days has it been since the victim was poisoned?

  • Step 1 set up your conversion factor

Neutron Activation Analysis

• A mean of identifying an individual based on hair

• looks at the concentration of 14 different elements in a hair shaft by bombarding them with radiation

  • Each element gives a different response

• The probability of two individuals having the exact same concentration for any nine of the elements is ~ one in a million

Testing The Hair Follicle

• Follicular Tag: The presence of the entire follicle on a hair sample

  • Happens when a hair is removed by force

  • Can be used for DNA Testing

    • Generally done after microscopic analysis to save time and money

Multiple Choice

True or False: Hair is less useful in identifying chemicals in the body than a blood or Urine Test

• True

• False

Multiple Choice

A comparison microscope is......

• the central core of a hair fiber

• material that connects an individual or thing to a certain group

• the tough outer covering of a hair composed of overlapping scales

• a compound microscope that allows the side by side comparison of the samples, such as of hair or fibers

Multiple Choice

Neutron Activation Analysis is an example of which type of evidence

• Class

• Individual

Multiple Choice

Where is Nuclear DNA found in the hair?

• hair shaft

• root or follicle

• tip

• medulla