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Forensic Procedures: Hairs and Fibres Essay

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Updated: Mar 24th, 2022

The changes in time have been associated with increased levels of crime. The continued cases of robbery, murder and rape have been countered with the adoption of various forensic procedures to bring the crime perpetrators to book. These methods include DNA analysis, face recognition, forensic odontology, forensic pathology, use of finger prints, hairs and fibers, criminal profiling and serology (Jackson, 2002). This paper outlines how hairs and fibres play a crucial role in the investigation of crime.

Biologists have always associated hair to dead cells. Hair primarily made up of keratin is characterized by differences in growing rates (Ramstard, 2006). For instance the head hair grows at a slower rate compared to the beard but at a faster rate compared to the body hair. The fact that hair does not decompose gives an edge over other forensic methods. The durability aspect has been applied to investigate criminal cases that date back several years.

It has also been established that hair depicts an absorbent quality which makes it possible to analyse levels of arsenic poisoning (Ditton, 2002). It is usually easy to ascertain whether the hair obtained fell off freely or was as a result of a tussle between the victim and the suspect. Hairs can be subjected to DNA profiling on condition that some root structures are available (Ramstard, 2006). Presence of hair on surfaces of vehicles after an accident is reminiscent of accidents. It is also correct to conclude that a crime weapon bearing a victim’s hair was used against him/her. It is this principle that is used to correlate certain events to crime investigations (Kelly & Phillip, 2004).

Fibres are commonly regarded as the basic units of clothing. Fibers may be of different length, strength and pliability depending on the type of fabric desired. Artificial and natural fibers are common. Natural fibers such as wool and cotton have been in existence for many years but the emergence of synthetic fibers has been accepted due to changes in tastes and preferences. Synthetic fibers include silk, nylon and polyester (Reffer & Welzel, 2007).

Structural fibres such as asbestos and glass fibres have also been introduced lately. The identification and analysis of natural fibers was simple just by observation and touching. It is usually difficult to identify synthetic fibres because of how designers have combined several varieties in order to achieve desirable results (Reffer & Welzel, 2007). However, it is possible to identify such fabrics through chemical and burning tests.

The discovery that hairs and fibres could indeed be useful in crime investigation came in the 19th Century. It was based on the premise that any struggle between a victim and attacker led to the transfer of hairs and fabric between them (Saferstein, 2000). The early 20th century saw the establishment of microscopic examination of hair. The development of this procedure has subsequently been used over the years to provide hints to crime investigators. Previous cases that have shown that hairs can be tools of crime investigation are well documented. A good example involves Mable Tattershaw who was strangled in 1951 (Saferstein, 2000).

A thorough examination on her clothes revealed some hair traces. The hair was subjected to a forensic laboratory examination only to reveal that it was identical to the head hair of Leonard Mills, the chief suspect. It is important to note that hair examination under a microscope can reveal too much information about a person. The race, sex and age of the owner can be ascertained (Ramstard, 2006).

The most striking feature, however, is the fact that hair cannot be destroyed apart from burning. Cloth fibres also find themselves attached to surfaces where crime must have been committed. Pieces of cloth that fit into each other may also be found. In most cases, tiny fibres are collected in crime scenes and what remains to be understood is how these fibres get attached on even smooth surfaces after a crime has been committed.

The collection of hairs and fibres is usually the first step in crime investigation (Ditton, 2002). It is when hairs and fibres have been collected that events can be reconstructed. Where and when the samples are collected is a great consideration made. The state of hair can reveal whether or not force was used in the crime. Availability of root structures is indicative of a forceful crime (Jackson, 2002). This factor can be used to characterise the nature of crime on the basis of venue or actions performed. Collection of hairs and fibres is achieved by use of a clear tape. The tape is applied on a surface and later removed carefully.

The use of various tapes is common depending on the stickiness desired. The efficiency of stickier tapes is high when recovering fibers. The fibers are normally extracted from the tape by use of a liquid (Ditton, 2002).

The identification of hairs and fibres is vital. It is important that the type is known long before the examination process begins. This helps to reduce cases of mismatch. Type of hair is not usually difficult to differentiate. Human hair, dog hair and cat hair are all different in color and texture. The presence of dog hair on a crime scene will automatically rule out the possibility of testing human hair in the laboratory. The identification of fibres is also vital in the crime investigation procedures.

As earlier stated, the identification of natural fibres is usually easy. Wool, for instance, can be easily differentiated from cotton by virtue of texture. It is however difficult to distinguish silk from polyester in cases where both have been combined to make a single fabric (Reffer & Welzel, 2007). Most synthetic fibres are produced through ester formation and cannot be easily differentiated on basis of observation under the microscope. Infrared spectrophotometry is usually used to make a distinct difference between synthetic fibres. The technology makes use of the absorption and reflective features of objects once subjected to a source of electromagnetic radiation (Kelly, 2007).

Absorption and reflection phenomena of the spectrum are used in the characterisation of fibres on the basis of how they absorb and reflect various parts of the visible spectrum. Absorption bands are usually formed on surfaces that appear dim when light is passed through surfaces. These bands form signatures that are easily detected by a spectrophotometer (Kelly, 2007). Fabrics may also absorb invisible wavelengths such as ultraviolet (UV) and infrared (IR) rays. The fact that infrared has a wider wave length compared to UV or visible band makes its application better since complete substance signatures is provided.

The analysis of hairs and fibres is usually a critical procedure that involves qualified forensic experts. Traditional analysis for hair that involves examination under the microscope is still very common today. Despite the fact that DNA analysis is still carried out, most forensic examinations employ the use of the traditional methods. DNA analysis has been associated with reduced levels of objectivity, reliability and high costs (Saferstein, 2000). Microscopic examination yields vital information regarding type of hair (animal or human), race, fall condition, species of animal, body part and how it was cut.

The value and direction of the DNA analysis is dependent on the preliminary examination carried out on the hair. The lack of root material for the hair means that no DNA analysis can proceed thereafter (Saferstein, 2000). Dry mounting of hair is usually done on a glass slide to allow comparative viewing under a microscope. A wax block provides a medium on which examination of a hair cross section is done. Microscopic view of the cross section of medulla is achieved. Cellulose acetate is important in the preparation of cuticular scales.

Several tests may be conducted by a scientist in regards to dyed hair. The success of a forensic laboratory examination depends largely on the work conducted on the crime scene (Saferstein, 2000). It is usually a natural advantage that hair has different loss and growing rates. Thorough examination of clothing can give traces of hair. The scientist may opt to change the natural appearance of the natural hair if he/she feels that matching can be achieved appropriately (Ramstard, 2006).

The scientist’s opinion of whether a match of sample hair and suspect’s hair is evident is enough proof that can be presented before a court of law. Murder investigations have been successful courtesy of hair examination. A good example that involved the buried remains of a murder victim is illustrated (Kelly, 2007). A body buried for five weeks revealed several outcomes regarding the identity of the victim, weapon of injury and the suspect. Laboratory examination of head hairs found on a branch purported to have been used to kill her was conclusive evidence.

Fibres that are examined and analysed by IR spectrophotometry involve a series of scientific steps. Sodium chloride finds its importance here. The mixing of the common salt and the fibre is done forming a disk (Reffer & Welzel, 2007). The fact that salt is transparent to IR rays make it more reliable for this exercise. The disk is then focused under IR light and observations made. The fibre absorbs parts of the IR radiation and reflects the rest. The chemicals present in the fibre are responsible for the absorption and reflective tendencies. The rays observed are characterised into a spectrum that gives differences in light intensities.

The varying light intensities are usually measured and plotted by the spectrophotometer. The device ensures electronic and graphical visualisation of the resultant wavelike characteristic output. The peaks and troughs are indicative of the absorption bands. A comparison of the signatures generated by these absorption bands is important for the scientist to correlate the characteristics observed to the substance. The quantity of compound present in a substance can easily be established (Reffer & Welzel, 2007). The origin of the fibres, concentration of fibre and the quality of fibre can be inferred from spectrophotometry (Reffer & Welzel, 2007).

A sample of fabric can generate questions such as; what are the weaving patterns? How are the edges of the cloth physically fitting to the fabric obtained from the crime scene? The answers to these questions can be obtained. The weaving patterns may be twill, plain, satin and pipe weave. The jig-saw fit of fabric elements may help in giving the assurance that the fitting parts are one. The burning tests and chemical tests can also be conducted by forensic scientists to identify and classify fibres.

Trace evidence examination is used to refer to forensic examination that involves the collection and analysis of samples such as hairs, fibres, paints and glass (Kelly & Phillip, 2004). It is important that the evidence remains undisturbed if objective conclusions are to be made (Jackson, 2002). Any form of interference makes the evidence useless before a court of law. Cross-contamination of hair and fibre samples may occur between the point of crime and the forensic laboratory.

The police officer involved may pick up a victims hair and purport that the same was found on the suspect’s clothes. It would therefore be very difficult to present such evidence before a court of law. Utmost care is required when handling, packaging and transferring hair and fibre evidence (Phillip & Bowen, 2010). Clear labeling of the evidence is paramount if good results are to be expected. A mismatch of samples may ensue especially in cases where evidence is lost.

The chain of custody protocol is usually vital for trace evidence (Phillip & Bowen, 2010). The protocol ensures that evidence is handled professionally from the crime scene to the court room. An item should be clearly labeled in order to avert possibilities of ambiguity. Any police officer and forensic scientist involved must sign against the evidence. Any form of contamination renders the evidence inappropriate for prosecution by a court of law (Phillip & Bowen, 2010).

Despite the intricacies of hair and fibre evidence, the method has widely been used to unravel criminal mysteries that have remained concealed over time. The fact that hair cannot be destroyed makes it appropriate in handling crimes that were committed several years ago. The method also enjoys a range of advantages such as; it provides detailed information such as age, race and type of hair. The application of this forensic procedure can therefore be of importance if due care is taken. The effective incrimination of a suspect can be ensured if all the norms of evidence packaging, handling and transport are adhered to.


Ditton, J. (2002). Human Hair Fibers. Journal of Forensic Science, 41 (1).

Jackson, A. (2002). Forensic Science and Crime investigations. Routledge Press.

Kelly, J. F. & Phillip, K. W. (2004). Tainting Evidence: Inside the Scandals at the FBI Crime Lab. New York: Free Press.

Kelly, P. (2007). Forensic Science Under Siege. New York Press : New York Press, USA.

Philip, J.H. & Bowen, J. K. (2010). Forensic Science and the Expert Witness. University of California, USA.

Ramstard, K. (2006). Microscopy of Hair. Forensic Science Communications Institute.

Reffer, J. & Welzel, D. (2007). Forensic Classification of Polyester Fibers by Infrared Recognition. Journal of Forensic Sciences, 45 (3).

Saferstein, R. (2000). Criminalistics: An Introduction to Forensic Science. New York: Prentice-Hall.

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