Hair anf Fiber Analysis

The history of Hair/fiber analysis:

In the early stages of forensic science the significance and value of examining hair during a criminal  investigation was realized. Published in France in 1857, one of the first scientific reports regarding trichology, 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.

Hair structure:

The part beneath the skin is called the hair follicle or when pulled from the skin, called the bulb. Each strand of hair is made up of the medulla, cortex, and cuticle. The innermost region is the medulla, is not always present and is an open, unstructured region. The highly structured and organized cortex, or middle layer of the hair, is the primary source of mechanical strength and water uptake. The tip is the very end of the strand.

Major types of fibers:

 -Cotton (left) is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants
 -Polyester is a category of polymers which contain the ester functional group in their main chain

-Silk is a natural protein fiber. Best known type of silk is obtained from the cocoons of the larvae of the mulberry silkworm

-Wool (right) is the textile fiber obtained from sheep and other animals

-Linen is a textile made from the fibers of the flax plant and it is valued for its exceptional coolness and freshness in hot weather.

Hair/Fiber collection techniques:

Collecting Hair:

 When recovering all hair present. If possible, use the fingers or tweezers to pick up hair, place hair in paper bundles 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.

Collecting Fibers:

Fiber evidence is often found in fabric abrasions or caught in torn materials or other areas on hit-and-run vehicles. In some burglary cases, it may be found caught in torn screens, broken glass, or other locations. Examination of fibers can normally be conducted to determine the type or color of fiber. Such examinations will sometimes indicate the type of garment or fabric from which they originated. Fibers and threads can also be compared with suspects clothing to determine whether or not they could have come from this clothing. If threads or large fibers are found, they can often be picked up with the fingers and placed in a paper bundle, and then in a coin envelope, which can be sealed and marked. Never place loose fibers directly into a mailing envelope since they can be lost from this type of envelope. If the fibers are short or few in number, and if it is possible to do so, wrap the area or the entire item containing the fibers in paper and send the whole exhibit in the Lab. 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 Lab for comparison purposes.

Typical Hair/fiber analysis and how scientists analyze and use hair/fiber data:

When analyzing hairs and fibers, a microscope is used to identify the difference between animal hairs and human hairs and differences between various fibers. Race can be determined within the use of a microscope, but age and sex are still indeterminable at this point. Comparing fibers found at the crime scene to those of the suspects and victims carpets, clothes, and car fibers is another way that scientists analyze the origin of the fibers. Through both of these methods, scientists are typically successful in determining criminals, suspects, and victims.

Reliability of Hair/fiber crime scene data:

Hair is class evidence, best case scenario: Human head hair has odds of 4500 to 12 of originating from the same person (0.0022%). Pubic hair has even better odds of 800 to 1.3 (0.00012%) Negroid and Mongoloid hairs tend to exhibit less variation and therefore usually lower odds. Because of these odds, although only a class characteristic, hair can be highly distinctive evidence. This means that hair is a highly effective use of forensics.

The Leanne Tiernan 

On August 2001, a man walking his dog in Lindley Woods, near Otley, in West Yorkshire, found the body of 16-year old Leanne Tiernan, buried in a shallow grave. This was about ten miles from her home in Landseer Mount, Bramley, Leeds. She had been walking home from a Christmas shopping trip with her best friend in November 2000 when she disappeared. When found she had a black plastic bag over her head, held in place with a dog collar, with a scarf and cable tie around her neck, and cable ties holding her wrists together. Her murderer had then wrapped her body in green plastic bin liners tied with twine. In the largest search in West Yorkshire, the police searched around 800 houses and 1500 gardens, outbuildings and sheds on her route from the bus stop to her house, as well as searches of a three-mile stretch of canal, drain shafts and moor land.

The pathologist examining her body said that it had not been there since November. She had been strangled and her body stored at low temperatures in the intervening time. The police tracked down suppliers of the dog collar and found that a man from Bramley had bought several similar to the one found around Leanne Tiernan’s neck. His name was John Taylor, and he was a poacher who had been seen around the woods where the body was found. The twine was an unusual kind, used for rabbit netting, and was tracked down to a supplier in Devon, which had only produced one batch. It matched twine found in John Taylor’s home. Some of the cable ties used on Leanne Tiernan were of a type used almost exclusively by the Royal Mail, the patent company of John Taylor’s employer, Parcel Force. When the police searched John Taylor’s house they found more of the cable ties and one of the dog collars. The scarf tied around Leanne Tiernan’s neck had a few hairs caught in the knot. Unfortunately, there was not sufficient DNA in the roots for standard DNA profiling. However, the scientists found very small amounts of DNA in the hair shaft and used mitochondrial DNA testing to match it to John Taylor. There were dog hairs on Leanne Tiernan’s body, and scientists in Texas produced a partial dog DNA profile – this was the first time a British murder investigation had used dog DNA profiling. However, John Taylor’s dog had died, so this could not be used in evidence. Forensic scientists found a strand of pink carpet fiber on her clothes, with specific patterns of dye. Though John Taylor had destroyed the carpet by burning it, police found strands around a nail that matched the fiber on her jumper. Searching under the floorboards, police found bloodstains that the forensic scientists identified as belonging to Leanne Tiernan. John Taylor was arrested in October 2001, and sentenced to two life sentences in July 2002. In February 2003, he was convicted of two rapes, based on DNA evidence, and given two additional life sentences.