Crim 409 Lecture 8

CRIM 409: FORENSIC SCIENCE LECTURE EIGHT: HAIR EXAMINATIONS

Why Is Hair Good Evidence?
Abundant - average person has >100,000 hair follicles on their head alone
Easily transfer - average person loses 100 hairs per day
Considerable variability - comparing body area alone, human hair can be from the head, pubic, anal, eye, nose, ear, underarm, leg, arm, chest, trunk, or beard area, not including the fine hair covering the entire body except on a person’s palms and soles
Durable - hairs have been recovered from mummies dating back 2,000 years

Hair
What crimes are hairs involved in?
Hairs are shed from people
Can link person to crime scene
Animal hair may also link person to crime scene

Introduction
Human hair frequently found at scene of violent crimes
Provides link between criminal and crime
From hair one can determine:
human v. animal source
race (sometimes)
origin from body
Whether hair was forcibly removed
If hair has been treated with chemicals
If drugs have been ingested

Hair Evidence
Found in many crimes, submitted to the laboratory.
Can include homicides, hit and runs, sexual assaults, kidnappings, burglaries, etc.
Suspect Object Scene Victim

Hair Shaft
Composed of:
Cuticle — outside covering, made of overlapping scales
Cortex — inner layer made of keratin and imbedded with pigment; also contains air sacs called cortical fusi
Medulla — inside layer running down center of cortex

Hair
How is hair analyzed?
Look at class characteristics (microscope):
Color
Medulla, Cortex, Cuticle

The Cuticle
…… outermost layer of hair which is covered with scales. Scales point toward tip of the hair. Scales differ between species of animals and are named based on their appearance
The three basic patterns are:
Coronal
Spinous
Imbricate

Animal Hairs Coronal scale pattern is found in hairs of very fine diameter. Coronal scales are commonly found in the hairs of small rodents and bats

Animal Hairs Spinous or petal-like scales are triangular in shape and protrude from hair shaft. Found on hairs of seals, cats, and some other animals. They are never found in human hairs

Animal Hairs Imbricate or flattened-scale type consists of overlapping scales with narrow margins. Commonly found in human hairs and many animal hairs

The Cortex
……… gives hair its shape and color
Contains:
Melanin — pigment granules

Hair Color

Dyed Hair

The Medulla
…… is the hair core that is not always visible. The medulla comes in different types and patterns
Types:
Intermittent or interrupted
Fragmented
Continuous
Absent — not visible!

Medulla Structure

Hair Shape
Can be straight, curly or kinky depending on the cross-section, which may be round, oval or flat:
Round (Straight) Oval (Curly) Flat (kinky)

Cross Section

Hair Growth Cycle

Hair Growth
Terminology
Anagen — hair that is actively growing; lasting up to 5 years
Catagen — hair is not growing; a resting phase
Telogen — hair that is dying and ready to fall out; lasting two to six months
Length — about 0.5 mm per day or 1 centimeter per month; approximately one half inch per month

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

Root Structure

Hair Comparison
Color
Length
Diameter
Distribution, shape and color intensity of pigment granules
Dyed hair has color in cuticle and cortex
Bleaching removes pigment and gives a yellow tint
Scale types
Presence or absence of medulla
Medullary pattern
Medullary index

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

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
25 full-length pubic hairs

Hair Toxicology
Advantages:
Easy to collect and store
Is externally available
Can provide information on the individual’s history of drug use or of poisoning.
Collections must be taken from different locations on the body to get accurate timeline

Hair Toxicology
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 the cause is attributed to vapors from dyes in the wallpaper

Summary of Potential Results
A qualified hair examiner can provide the following information
from a hair examination and comparison:
1. Whether there is hair(s) recovered from item(s) submitted.
2. Racial origin of hair (Caucasian-type, Negroid-type, Mongoloid-type)
3. Area of body that hair came from (head, pubic, body)
4. Whether hair has been artificially treated
6. Whether there has been damage to the hair
7. Whether there are similarities and/or differences between the questioned hair and known sample.
*How much information an examiner can provide depends upon suitability of hair.

Hair Examination Conclusions
A hair examiner can conclude the following:
1. Questioned hair exhibits similar characteristics (no significant differences are present) to known sample. Thus, source of known sample cannot be excluded as being source of questioned hair.
2. Questioned hair exhibits dissimilar characteristics to the known sample. Thus, the source of known sample can be excluded as being source of questioned hair.
3. Questioned hair exhibits both similarities and differences to known sample. Thus, no conclusion can be reached
4. Known hairs insufficient or unsuitable for comparison purposes.
5. Questioned hair(s) insufficient or unsuitable for comparison purposes.

Postmortem Root Banding

Crim 409 Lecture 8

by Theangeloflaw on Nov 10, 2009

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Crim 409 Lecture 8 — Presentation Transcript