Chapter 3: Hair Analysis

Follicle
Shaft

Hair consists of these 2 parts.

Follicle

club shaped structure in the skin

papilla

What is at the end of a hair follicle?

Papilla

Network of blood vessels which supply nutrients to feed the hair and help it grow

Bulb

This surrounds the papilla and is associated with the sebaceous gland

Sebaceous Gland

Secretes oil that helps keep the hair conditioned and is associated with the bulb

Erector Muscle

Causes hair to stand upright and attaches to the bulb.

Nerve Cells

cells which wind around the follicle and stimulate the erector muscle in response to changing environmental conditions.

Keratin

The hair shaft is composed of this protein which is produced in the skin; it makes hair both strong and flexible.

Root

Part of hair follicle which must be present for DNA to be extracted, amplified, and compared to known samples for identification

Compound Microscope

This tool uses more than one lens to magnify a hair when no root is present so that it can be matched by other characteristics

Inner Medulla
Cortex
Outer Cuticle

The hair shaft is made up of 3 layers:

Imbricate

narrow, flattened, overlapping cuticle scales commonly found in human hairs.

Cuticle

Transparent outer layer of the hair shaft made up of imbricate scales that overlap one another and protect the inner layers of the hair.

Direction

When examining a section of hair under a microscope, noticing the __________________ the scales point shows the younger and older ends of the hair.

Cortex

In humans, the _______________ is the largest part of the hair shaft.

Melanin

Pigment granules within the cortex that give the hair its color

Near the cuticle

Commonly, the pigment is denser in what part of human hair?

Medulla

Center of hair
Hollow tube or filled with cells
Absent in some people, in others it's fragmented, and in others it's continuous or even doubled.
Contains pigment granules or is unpigmented

5

Forensic investigators classify hair into ____ different groups depending on the appearance of the medulla

Shape
Length
Diameter
Texture
Color

Hair type can vary in what five ways?

Circular
Triangular
Irregular
Flattened

How can hair be shaped which can influence curl pattern?

Texture

The ________________ of hair can be coarse as it is in whiskers or fine as it is in younger children.

Color

Hair ______________ varies depending on the distribution of pigment granules and on hair dyes.

50 hairs from the head 25 hairs from the pubic region

Because inconsistencies occur within each body region, how many hairs are usually collected from a person's head and pubic region?

6

Forensic scientists distinguish how many types of hair/regions on the human body?

Head hair
Eyebrows & Eyelashes
Beard & Mustache hair
Underarm hair
Auxiliary or Body hair
Pubic hair

What are the 6 hair regions which forensic scientists distinguish?

Cross-sectional

One of the ways in which hairs from the different parts of the body are distinguished is their ___________________________ shape.

Head hair

Hair from this region is generally circular or elliptical in cross section.

Eyebrows & Eyelashes

Hairs from this region are circular but often have tapering ends.

Beard hairs

Hairs from this region tend to be thick and triangular, is usually coarse, and may have a double medulla.

Body hair

Hair from this region can be oval or triangular, depending on whether regularly shaved.

Pubic hair

Hair from this region tends to be oval or triangular; the diameter may vary greatly, and buckling may be present.

Arm/Leg hair

Hair from this region usually has a blunt tip, but may be frayed at the ends from abrasion.

5

There are ____ different patterns of medulla which are identified in forensic hair analysis.

Continuous

Medulla pattern which is one unbroken line of color

Interrupted (Intermittent)

Medulla pattern described as pigmented line broken at regular intervals

Fragmented (Segmented)

Medulla pattern of a pigmented line unevenly spaced

Solid

Medulla pattern where pigmented area fills both the medulla and the cortex

None

Medulla pattern where there is no separate pigmentation in the medulla

100

You lose approximately ______ hairs from your head each day.

3

The Life Cycle of Hair: Hair proceeds through ____ stages as it develops.

Anagen stage

1st stage of hair development
Active growing stage of hair (cells around follicle rapidly dividing/depositing materials within hair)
Lasts @ 1,000 days
80-90% of all human hair is in this stage.

Catagen

Brief transition period between the growth and resting phases of a hair follicle
Hair may turn gray
2% of all hair growth/development

Telogen

(resting or dormant phase) the final phase in the hair cycle that lasts until the fully grown hair is shed/lost
10-18% of all hairs are in this stage

Pattern

There is no __________________ as to which hairs on the head are in a particular stage of the life cycle at any time.

Bleaching

Doing this to hair removes pigment granules and gives hair a yellowish color.
It makes hair brittle and can disturb the scales on the cuticle.
Artificial-shows a sharp demarcation
Sun-leaves a gradual mark

Dyeing

Doing this to hair changes the color of the hair shaft. An expert forensic examiner can immediately recognize the color as unnatural.
The cuticle and the cortex both take on this color as well.

1.3 cm per month
0.44 mm per day

Human hair grows at what rate?

Dividing

Measuring the length of hair that is natural in color and ______________ by 1.3 cm provides an estimate of the number of months since the hair was colored.

European hair characteristics

Appearance: generally straight or wavy
Pigment Granules: small & evenly distributed
Cross Section: oval or round of moderate diameter w/ minimal variation
Color may be blonde, red, brown, or black

Asian hair characteristics

Appearance: Straight
Pigment Granules: Densely distributed
Cross Section: Round w/ Large diameter
Shaft tends to be coarse & straight
Thick cuticle

African hair characteristics

Appearance: Kinky, curly, or coiled
Pigment Granules: Densely distributed, clumped, may differ in size & shape
Cross Section: Flattened w/ moderate-small diameter & considerable variation

Pattern of Pigmentation
Medullary Index
Cuticle Type

What are 3 differences in animal and human hair?

Human hair-denser toward cuticle
Animal hair-denser toward medulla

How does the pattern of hair pigmentation differ in humans vs. animals?

Ovoid Bodies

Solid masses of animal hair pigmentation especially in dogs and cattle.

length

Human hairs are usually one color along the _____________.

banded

Animal hairs can change color abruptly in a ____________ pattern.

Medulla

In animals, the _____________ is much larger than it is in humans.

Medullary Index

the ratio of the diameter of the medulla to the diameter of the entire hair

Animal

If the medullary index is 0.5 or greater, the hair came from an _______________.

Human

If the medullary index is 0.33 or less, the hair came from a _________________.

Continuous

The medulla of animal hair is much larger than in human hair, and it is always ___________________.

Cuticle

The ______________ of the hair shaft can also help distinguish human hair from animal hair.

Mammal

There are different cuticle types in different ________________ hair cuticles.

Coronal

Rodents and bats have a ___________________ cuticle with scales that give the appearance of a stack of crowns.

Spinous

Cats, seals, and mink have scales that are called _______________ and resemble petals.

Imbricate

Human hair has cuticle scales that are flattened and narrow, also called _______________.

Locard's Exchange Principle

Whenever two objects come into contact with one another, there is transfer/exchange of materials between them.
Reasoning behind the use of trace evidence; if a person is at a crime scene, they will leave/pick up some trace evidence.
One of the major examples of trace evidence is hair.

Plucking
Shaking
Scraping
Sticky tape
Vacuuming

What are some ways in which investigators collect hair evidence?

body regions

If a large number of hairs are collected from a victim or crime scene, an investigator will compare the sample with hair taken from the six major ____________ ____________ of the victim or suspect(s).

Macroscopic

Length, color, and curliness are ______________________ characteristics.

Microscopic

Pattern of the medulla, pigmentation of the cortex, and types of scales on the cuticle are ____________________ characteristics.

Fluorescence

Microscope that uses a beam of light of a certain color so that if a sample contains particular chemicals, it will absorb some of the light and then reemit light of a different color. *Many dyes and other hair treatments will fluoresce under a certain color of light.

Electron

This microscope provides incredible detail of the surface or interior of the sample, magnifying the object 50,000 times or more.

chemicals

Because hair grows out of the skin, ______________ that the skin absorbs can become incorporated into hair.

toxins

Ingested or absorbed __________________ such as arsenic, lead, and drugs can be detected by chemical analysis of hair.

keratin

During testing, the hair is dissolved in an organic solvent that breaks down the _________________ and releases any substances that have been incorporated into the hair and chemical tests can be performed to detect the presence of various substances; can provide evidence of poisoning or drug use.

decompose

Because hair does not readily ____________________, by testing different parts of the hair, it may be possible to establish a timeline for when exposure to poisons or other toxins might have occured.

Neutron Activation Analysis (NAA)

Technique that can identify up to 14 different elements in a single 2 cm long strand of human hair. Different elements will give off gamma radiation with different signals which can determine concentrations of elements in the sample.

million

The probability of the hairs of 2 individuals having the same concentration of nine different elements (antimony, argon, bromine, copper, gold, manganese, silver, sodium, and zinc) is about one in a _________________.

Follicular Tag

Tissue from a hair follicle that is still attached to the root end of a hair.
*DNA analyses can be performed and can also identify the blood type of a suspect.

cost effective

In many cases, a microscopic assessment of hair is performed initially because it is more _______ _____________ and rapid that blood protein and DNA testing. If a microscopic match between a suspect and a sample is found, then the samples will be forwarded for blood and DNA testing.

class evidence

DNA analysis of the hair follicle provides an identification with a high degree of confidence, whereas analysis of the hair shaft usually provides ___________ _____________ only.

hair

This is a character shared by all mammals and functions in temperature regulation, reducing friction, protection from light, and as a sense organ.

follicle
shaft

Hair consists of a ________________ embedded in the skin that produces the _____________.

Shaft

Composed of the protein keratin and consists of the outer cuticle, a cortex, and an inner medulla, each of which varies among individuals or species.

originates

Hair varies in length and cross-sectional shape, depending on where on the body it _______________.

developmental

Hair is broken into 3 _______________________ stages, called the anagen (growth), catagen (growth and change), and telogen (dormant) stages.

1934

The use of the comparison microscope to perform side-by-side analysis of hair collected from the crime scene and hair from a suspect or victim first occurred in:

secondary transfer

Hair can adhere to clothes, carpets and many other surfaces and be transferred to other locations. This is called:

trace evidence in criminal investigations in the late 1800s

Investigators recognized the importance of hair as:

hair in forensic investigations

A classic 1883 text on forensic science, The Principles and Practice of Medical Jurisprudence by Alfred Swaine Taylor and Thomas Stevenson contains a chapter on using:

most animals

In 1910 a comprehensive study of hair titles The Hair of Man and Animals was published by the French forensic scientists, Victor Balthazard and Marcelle Lambert. This text includes numerous microscopic studies of hair from:

5 million; 2%

When humans are born, they have about ___________ hair follicles, only _____ are on the head.