Hair Evidence and the Crime Scene
Hair evidence is discovered practically at every crime scene and may play a vital role in the process of investigation. Even a single hair strand may contain some information about a person's age, sex, race, occupation, disease history, and family background. The purpose of this study is to discuss the value of hair evidence and to reveal its potential by mentioning the discoveries that can be made from its analysis. The research is conducted on the basis of the observational method by collecting the data from academic sources and using it to define the significance of hair evidence. The paper considers the hair structure, the differences between hair samples taken from different regions of the body, the attributes of hair that make it valuable for forensic science, the ability to identify the perpetrator on the basis of hair evidence, and the methods of hair evidence collection. The current research defines the information that can be potentially obtained from the forensic analysis of hair samples and stresses the role of hair evidence in any type of crimes.
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Hair is commonly discovered at the crime scene as biological evidence that can be related either to a victim or to a perpetrator. Depending on its condition and the integrity of its structure, a hair sample may serve as a sufficient source of information about its owner. The inability to define the criminal by analyzing his hair sample does not diminish the fact that hair evidence can reveal the details of any crime and play a vital role in the process of investigation.
Hair as a Biological System from the Forensic Perspective
The analysis of hair as forensic evidence requires the examination of its three primary components. As stated by Erickson, they include cuticle, cortex, and medulla. The analysis of the cuticle that forms a transparent outer layer of the hair shaft can contribute to understanding of the hair attributes and the forensic identification of species. According to Erickson, the middle layer of the hair shaft defined as the cortex contains the color of the hair strand and has the greatest value for the forensic investigation. The central component of the hair shaft, namely the medulla, is individually determined and can vary between different hair strands. Therefore, it can be analyzed by the forensic experts to determine whether the hair sample belongs to human or an animal and define the racial origin of the suspect. The individual identification on the basis of hair evidence can be performed only in case of the presence of a follicular or skin tag that contains DNA. Thus, the results obtained from the analysis of hair evidence depend on the quality of a sample and the presence of its structural parts.
Hair Samples from Different Parts of Body
Even the hair samples belonging to the same person can vary if taken from different regions of the body. In terms of the forensic science, hair evidence that belongs to human is usually classified into six categories, namely head hair, eyebrows and eyelashes, mustache and beard, underarm hair, body hair, and pubic hair. To distinguish the origin of a hair sample, the experts consider its cross-sectional shape and physical features. For instance, although both head hair and eyebrows or eyelashes are circular in cross section, the latter usually have tapering ends. As stated by Bertino and Bertino, beard hair is mostly thick and triangular, pubic hair is oval or triangular, and the shape of body hair depends on whether the body region has been shaved. The tips of hair samples from the arms and legs are usually blunt, though they may be partly frayed from abrasion. Coarse hair with double medulla is usually considered as a sample from the beard. Pubic hair may significantly vary in diameter and can be distinguished by buckling that is present in the form of abrupt changes in the shape of the hair shaft. Therefore, the shape and physical characteristics of a hair sample may indicate the region of the body where it comes from.
The Importance of Hair as Forensic Evidence
The Value of Hair as Evidence
A single hair strand discovered at the crime scene can serve as a sufficient source of information about its owner due to a number of factors. First of all, hair responds to practically all environmental exposures and biological processes experienced by an organism. Even after the initial stage of its active growth that lasts for nearly 1,000 days, hair contains everything that is ingested by an individual or absorbed through his skin. Due to its tough outer coating, hair does not easily decompose and can serve as a material for different analyses and tests. The examination of hair parts enables the scientists to establish a timeline of a victims or suspects exposure to drugs or toxins. Hair easily adheres to clothes and other surfaces and can be transferred to other locations. Consequently, hair of the victim may be discovered at a secondary location, such as the suspects home or his belongings. Finally, a hair sample with a present follicle contains the DNA of an individual to whom it belongs. All these properties of hair increase its value for the forensic investigation.
Hair as a Vital Piece of Evidence in Any Crime
Any hair evidence discovered at the crime scene can reveal some details about its owner, be it a victim or a perpetrator. At present, hair is widely used for the identification of the age, sex, color, race, diet, disease profile, environmental and occupational exposure, geographical location, maternity and paternity characteristics and provides information about a persons exposure to toxic substances or poisoning incidents. For instance, male hair contains more of lead and copper while females have high amounts of calcium and nickel. High concentration of metals, such as mercury, arsenic, lead, and cadmium or other contaminants obtained by the environmental influence can serve as an indicator of air pollution characteristic to particular geographical area. Poor hair condition usually reflects the presence of diseases or hormonal imbalances.
Identification of the Perpetrator on the Basis of Hair Evidence
Although being a vital piece of evidence, a hair sample cannot point directly to a suspect and definitely identify him as the perpetrator of a crime. Hair evidence discovered at the crime scene can be compared to samples obtained from the suspects to determine whether they could belong to the same source. However, even in case of matching, the results of analysis cannot be treated as absolutely precise ones without the possibility of DNA analysis. Besides, the presence of suspects hair at the crime scene cannot serve as a proof of his guilt since it is not possible to determine the time when it was left there. In case of the absence of the suspect, hair evidence may serve as a means to exclude the members of a victims family as the possible perpetrators. Since the forensic science is based on the connection of multiple facts, a single piece of evidence can define a criminal only in very rare cases.
The Collection of Hair Evidence at the Crime Scene
When entering the crime scene, the investigators have to collect all hair samples that are present there. One of the methods of hair evidence collection is placing tape over a surface to make the hair adhere to it. To collect all hair samples from a large surface, the experts may use the vacuuming method. Besides, hair samples should be taken from the victim and the potential suspects in accordance with the recommended methods of hair collection. An individual has to bend over a large piece of clean paper and rub his hands through the hair making loose hairs fall out onto the paper. To get the additional samples, an expert should pluck them from various areas of a persons head. The obtained hair evidence has to be handled with tweezers and put in paper bindles that are subsequently folded and sealed in larger envelopes. In the course of this procedure, hair evidence is less likely to be damaged and may preserve the DNA sample.
To conclude, hair evidence discovered at the crime scene can play a vital role in the process of crime investigation. The analysis of structural components of a hair sample may disclose some information about a persons age, race, health condition, location, family background, and occupation. Although hair evidence can relate a suspect to a particular crime, it cannot be treated as an incontrovertible proof of guilt and is usually considered in complex with other types of evidence.
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