Fibres and hairs are important evidence that can be collected at crime scenes. Fibres come from clothing, carpeting, and other materials and can be natural like cotton, silk, and wool or man-made like polyester and nylon. Hairs come from humans and animals. Analysis of fibres and hairs examines characteristics like cuticle patterns, medullas, pigmentation, and damage to help determine type, match samples, and provide clues in criminal investigations. While not definitive, fibre and hair evidence combined with other factors can help corroborate relationships between suspects, victims, and crime scenes.

1. Forensics of Fibres

2. What is a fibre?
• A fibre is the smallest unit of a textile material.
• Fibres can occur naturally or be man-made.
• A fibre can be spun with other fibers that can be
woven or knitted to form a fabric.
• The type and length of fibre affects how easily
it transfers from person to person.

3. Fibre Evidence
• Fibres are gathered at a crime scene with
tweezers, tape, or a vacuum.
• They generally come from clothing,
drapery, wigs, carpeting, furniture, and
blankets.
• For analysis, it is first decided whether it
is natural, man made, or a mix of both.

4. Cotton
from a
plant
Silk from
the silk
worm
Wool
from
sheep
Linen
from the
flax plant
Hair fibres
from rabbits
& goats

5. Plant fibres made
from the organic
compound
cellulose
Flax
Wool Silk
Cotton
Cashmere
Animal fibres
made from the
organic compound
protein
Angora

6. All fibres
come in
different
lengths. Some
are short
some are
long!
Flax
Wool
Cotton
Angora
25cm-
150cm1cm-6cm
7.5cm-12cm
6cm-10cm
6cm-20cm Cashmere
They are all
called
STAPLE
fibres

7. Silk is the
EXCEPTION
because it is
very long! Up
to 1km which
is what we
call endless.
They are all
called
FILAMENT
fibres
Worm
Cocoon
Fibre
Fabric

8. Natural Fibres
Cotton fibres are the
plant fibres most
commonly used in
textile materials.
Cotton fibres

9. Other plant fibres
• Flax (linen), ramie,
sisal, jute, hemp,
kapok, and coir.
• The identification of
less common plant
fibres at a crime scene
or on the clothing of a
suspect or victim would
have increased
significance.
Flax fibers viewed
with
polarized light

10. Animal Fibre: Wool
• Wool is the most frequently
used.
• The most common wool fibres
originate from sheep.
Wool fibres

11. Man-Made Fibres
• More than half of all
fibers used in clothes
are man-made.
• Polyester and nylon
fibres are the most
common man-made
fibers, followed by
acrylics, rayons, and
acetates.
Cross section of
man-made fibers

12. Why are fibres important?
• The number fabrics produced with any one fibre
type and colour is extremely small.
• The likelihood of two or more manufacturers
exactly duplicating the textile is extremely small.

13. Fibre Number
• The number of fibers on the clothing of a
victim identified as matching the clothing
of a suspect is important in determining
actual contact.
• The greater the number of fibres, the
more likely that contact actually occurred
between these individuals

14. Fibre Evidence
• The problem with fibre evidence is that
fibres are not unique.
• Unlike fingerprints or DNA, they cannot
pinpoint an offender in any definitive
manner.
• There must be other factors involved, such
as evidence that the fibres can
corroborate or something unique to the
fibers that set them apart.

15. Hairs
Naturally shed has a
clubbed shaped end
Stretched
If there is skin attached DNA can be extracted

16. Cuticle
• The cuticle of a hair is the
thin, clear layer around the
shaft.
• It consists of scales of hard
protein that varies between
animal species.
• The patterns are:
– Coronal, or “crown – like.”
typical of rodents.
– Spinous, or “petal – like.”
Common in cats, seals, and
minks.
– Imbricate, or “flattened.”
Humans.
Coronal
Spinous
Imbricate

17. Cuticle
Photomicrograph of a
mink hair possessing a
Spinous cuticle.
Photomicrograph of
a bat hair
possessing a Coronal
cuticle.
Photomicrograph of a human
hair possessing an Imbricate
cuticle.

18. Medulla
Photomicrograph of a
human hair with no
medulla.
Photomicrograph of a
hair with trace medulla.
Photomicrograph of a hair
with a clear, continuous
medulla.
The medulla is a central core of cells that runs
through the center of the cortex.

19. Types of human hair
Photomicrograph of an
African Head Hair
– Curly, wavy or
coiled
– Large pigment
granules that
clump
Photomicrograph of an
Asian Head Hair
– Coarse straight
– Thick
– Large pigment
granules
– Reddish
Photomicrograph of a
Caucasian Hair
•Fine to medium
•Straight or wavy
•Blonde, brown, black
•Even pigmentation

20. Race and AgeEvidence From Hair
Hair can be examined to find out:
•Race
•DNA and Sex
•Age (sometimes)
•Hair colour (natural or dyed)
•Evidence of a struggle
AGE
Elderly
Pigment loss
Finer
Diameter of
hairs varies
more
Treated hair
Dyes or rinses are identified using a microscope
By measuring the length of the untreated part from the root, the time of
treatment can be guessed
Direct, side-by-side comparison of the colour of suspect’s hair and the
sample

21. Body hair
Head
Hair
Beard
Hair
Pubic
Hair

22. Practical
• Part A
• Use the microscopes to look at the samples of fibres and animal hair.
• Draw a labelled diagram of what you see. (Use your notes as a guide)
• Can you identify which are natural or man-made fibres or animal hair?
• Part B
• Look at your hair under the microscope.
• Do you dye/straighten your hair? Do you sunbathe a lot? If so you should be
able to see the damage you are doing to your hair.
• Compare with your friends.
Damaged