Any evidences left behind by the perpetrator at the crime just by trace amounts play a very crucial role in his/her conviction. Just like any other evidence, like hair, paint or soil, fibre becomes a very much crucial piece of evidence as it is reasonable that fibres compose the fabric and garments.
As per definition given by Paul.L.Krick (1902-70), anything touched or any mark or any blood traces left behind unconsciously may become mute evidences against him/her.
It is clear by now that fibre is a component that easily transferred and cross-transferred in daily life without any difficulty. In cases that involve personal contact like sexual assault, struggle prior to death, or even burglary or murder fibre from the garments are easily found as a source to frame suspicion.
The definition of fibre can be given as follows:
1. Fibres are tough, pliable and filament like substances that are composed of long chain like structures which are a combination of several units (molecules).
2. Fibre is the smallest visible unit which can be spun in to a textile, a polymer can be classified as a fibre only when its length is more than 100 times its diameter.
IMPORTANCE OF FIBRE
They can serve as an important evidence for various reasons, some of them can be:
1. They get easily transferred
2. In case of multiple transfers found from various locations, they can be used to link a series of events.
3. There are objects like carpets that are made from specific fibres and have distinct properties.
Hence, due to their properties, the specific type of source can be found.
4. Fibres are made using various colours, dyes and pigments resulting in thousands and hundreds of hues. And so a fibre found at random scene having same colour and microscopic properties provides good and strong evidence.
Through the introduction it is made clear that indeed fibres are a great source of undeniable evidences especially when personal contact is involved. But due to various methods applied after the processing of raw material, it becomes a bit difficult to match the fibres just by physical appearance and hence many other tests and analysis methods are applied.
CLASSIFICATION OF FIBRES:
Fibres can be classified as follows:
(FIBRES; NATURAL; SYNTHETIC; PLANT SOURCE; ANIMAL SOURCE; MINERAL SOURCE; ORGANIC; REGENRATED; INORGANIC) NATURAL FIBRE:
As the name suggests, these are the type of fibres obtained from the natural resources. These resources include plants, animals and minerals. Usually these are obtained as long thin filaments with negligible diameter similar to a thread. They can be spun or twisted into a yarn like a cloth and then can be processed into various clothing forms.
Depending on the source they are divided into three types as:
a) Plant sources:
These are the most commonly used fibres. These include the ones from cotton, flex, hemp, jute, sisal, coir. They contain cellulose and can be extracted from the stem, seed hair, leaf, or husk of a plant.
b) Animal sources:
These are the natural fibres that contain largely of particular proteins. Instances are silk, hair/fur(wool) and feathers. The most commonly used both in manufacturing world as well as by the hand spinners are wool from domestic sheep and silk. Also popular ones are the fur from alpaca and from angora goats
c) Mineral source:
The only known mineral source for fibre is Asbestos. They are extensively used as insulating materials.
SYNTHETIC FIBRES:
These are those type of fibres that are made from materials that are chemical polymers like nylon, polyester, acrylic, Teflon, polypropylene. They are created by extruding fibre-forming materials through spinnerets into air and water, forming a thread. Depending on their chemical composition they are classified as follows:
a) Regenerated fibre:
These are also known as semi synthetic fibres. Usually it is a machine made fibre that uses regenerated cellulose from cotton, wood or other plant source. E.g: rayon, acetate and triacetate.
b) Organic fibres:
Organic fibres are made with the extracts from natural sources. The reason why they don’t fall under the category is that, these type of fibres derive their main components from a polymer(natural/synthetic) and are then processed to synthesise the desired product.
c) Inorganic fibres:
Inorganic fibres are those that have inorganic materials like glass, carbon, metal, etc as their base component. Usually they are called are high performance or super fibres.
COLLECTION AND PRESERVATION OF FIBRES:
Prior to collection of fibre evidence from a crime scene the following points must be kept in mind:
· The size container where the sample is stored must correspond to the size of the evidence sample.
· No wet evidences should be packed prior to packaging. Fibres or objects contusing fibres must be air dried before placing in sealed containers.
· If the packaging of evidences is done on a surface it is important to make sure that the surface is completely and thoroughly cleaned and also that cross contamination must be avoided at all cost
· All the seams of packaging must be sealed to avoid loss of trace evidences.
Methods applied:
1. When the fibres are visible and are firmly attached to an inanimate object that can be sent to the laboratory.
· The fibres must be left intact and the object must be packed in a container so that the fibres are not lost during transit.
2. When fibres are visible and are not firmly attached, or if firmly attached to an object that is too large to be sent to laboratory.
· In this case, after noting down the details like the number of fibres and their location, clean tweezers must be used to remove the fibres.
· These fibres must be stored in a small pill box, glass vial or any other tightly sealed container. Druggist folds can also be used
3. When fibres are possibly transferred to the clothing of victim or suspect.
· The clothing must be dried before packaging
· Each item (shirt, trousers, etc) must be kept separately.
· Avoid any foreign materials stuck to the clothing.
4. When the fibres are in the hair of victim or suspect.
· The individual’s hair must be combed using a clean-fine toothed comb over a clean white paper.
· The paper must be folded together with the comb into a bundle and then place the bundle in an envelope.
Collection of fibre for standard examination:
When fibres are collected from the crime scene it is imperative that appropriate and adequate standard samples should also be submitted by the said official. For example, if fibres are found on the foot prints , standard samples from the underlying material, can be a carpet, should be sent to the forensic laboratory as well. The standard sample should be representative one with all the variations included.
PHYSICAL EXAMINATION:
The standard or the question sample is examined physically with first an hand magnifying lens and later with a stereomicroscope. The reason for using these instruments is very much evident because the fibres obtained may be in form of thread and hence to know the proper count it is impossible to do it with naked eye and even if it is a piece of fabric, the detail examination requires instrumental usage.
The following observations are done:
1. The twist of the thread. Usually fibres are twisted together to form threads and then the strings and hence the pattern twist may help in determination of the type thread. for example cotton has twists at irregular intervals.
2. The number of ply. Here ply number means the number of yarns twisted together to make a single thread.
3. The number of threads in a single string.
4. The number of fibres in each thread
5. The thread count if the fabric is obtained
References
Class notes
Md.Sohanur Rahman Sobuj : Man-made fibres and classification of man-made fibres
Fibrenamics : Inorganic fibres
SkillSoft Corporation: Fibres and their properties
Indiana State Police Laboratory Division: Fibre evidence
V.N Sehgal: Forensic science in criminal investigation and court evidence.
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