Hair and Fiber Analysis

History of Hair and fiber:
In France in 1857, one of the first scientific reports regarding the scientific study of hair, introduced the world to the idea. The field expanded rapidly after microscopic hair examination became known in the early 20th century. Fibers let scientist know what kind of clothing the suspect was wearing. Fibers are synthetic and must be identified with infrared spectrophotometer. scientists determine fibers by the way it absorbs light.

Hair is composed primarily of proteins, these proteins are of a hard fibrous type known as keratin. The cuticle is a translucent outer layer of the hair shaft consisting of scales that cover the shaft. The medulla is a central core of cells that may be present in the hair. The cortex is the main body of the hair composed of elongated and fusiform (spindle-shaped) cells. Papilla is a small nipple like projection, such as a protuberance on the skin, at the root of a hair or feather. Hair is a protein that grows out of hair follicle in the skin. Normally, a hair grows in the hair follicle for many months, stops growing, and falls out. A new hair then grows in the follicle. It takes weeks for a hair sample to show changes in the body, because hair grows slowly. Hair samples do not show recent changes in the body, such as drug use within the past few days.

Major types of Fibers:

• cotton
• silk
• wool
• nylon
• polyester

The two broadest groupings of fibers are Natural and Man-Made. Natural Fibers –derived in whole from animal or plant sources. Examples are wool,cotton, and silk .Man-Made fibers- fibers made totally from man made materials (synthetic fibers) or chemically altered natural materials. Synthetic: nylon and polyester.

Hair/Fiber collection techniques:
Use the fingers or tweezers to pick up hair, place in paper bindles or coin envelopes which should then be folded and sealed in larger envelopes. Label the outer sealed envelope.If hair is attached, such as in dry blood, or caught in metal or a crack of glass, do not attempt to remove it but rather leave hair intact on the object. If the object is small, mark it, wrap it, and seal it in an envelope. If the object is large, wrap the area containing the hair in paper to prevent loss of hairs during shipment.


If threads or large fibers are found, they can often be picked up with the fingers and placed in a paper bindle, then in a coin envelope, which can be sealed and marked. If the fibers are short or few in number wrap the area or the entire item containing the fibers in paper and send the whole exhibit to the Laboratory. Pick up fibers on tape only if the laboratory in your jurisdiction allows it and gives you its requirements. When fibers or threads are recovered, always send all clothing of persons from which they might have originated to the Laboratory for comparison purposes.

Typical Hair/fiber analysis:

Hair is used to help identify a criminal by evaluating their hair structure and DNA. Hair samples are tested with specific chemicals and looked at under a microscope. Hair analysis can also be used to check for poisoning caused by metals such as lead or mercury. This makes hair very reliable because it containsyour DNA.

Fiber is often the most common type of evidence found at a crime scene. Importance is usually magnified in cases of homicide, assault, or sexual offences. Fibers may be found caught in screens, or on jagged surfaces, around broken glass, on cars involved in pedestrian hit and run or transferred during a struggle.Most of fiber analysis is done through microscopic examinations. When analyzing under a microscope, you try to identify color, texture, shape pattern, cross sectional appearance, and surface characteristics. Micro-chemical tests which are various chemical reagents that are used for determining physical characteristics of the fiber such as melting point, density, ash formation, tensile strength, solubility.