Hair and Fiber Analysis




Hair and Fiber Analysis

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For the success of an investigation, trace evidences found at crime scenes are identified and compared. These evidences consist of materials or substances that are generally small in size and can be transferred when physical contact occurs between two individuals, objects or an individual and an object. Hairs and fibers are examples of such evidences. The transfer of hairs and fibers can be critical in associating a suspect to a victim or a crime scene. However, analysis of these evidences requires the understanding of its dynamic nature such as knowing how these can be transferred and the factors that affect the significance of a match in crime scene investigations.



Hair Evidence

Hairs are composed mainly of the protein keratin and can be defined as slender outgrowths of the skin of mammals. Although it is considered as a benign dead matter, it still contains DNA even though it is not a living organism.

Variability exists in the types of hairs that are found on the body of an animal or human. For humans, hairs found on different parts of our body even have characteristics that can determine their origin. Due to the fact that hairs can be transferred during physical contact, its presence can be associated with a suspect to a crime scene. Comparison of the microscopic characteristics of questioned hairs to known hair samples helps in determining whether a transfer may have occurred.

Types of human hair that can be found at crime scenes:

1. Naturally shed hair – display undamaged, club-shaped roots

2. Forcibly removed hair

    a. exhibit stretching and damaged to the root area
    b. may have tissue attached

Types of Human Hairs:

    1. Head hair – with uniform diameter and often has cut tip
    2. Pubic hair – course and wiry and has diameter variation or buckling
    3. Facial hair – coarse in appearance and can have a triangular cross section
    4. Limb hair – shorter in length, arc-like in shape and often abraded or tapered at the tips
    5. Fringe hair – might originate from the neck, sideburns, abdomen, upper leg, and back
    6. Other body area hair – underarm, chest, eye, and nose hairs

Collection and Packaging of Hair Samples

    1. Known human hair samples should consist of at least 25 combed and pulled hairs
    2. Hair samples from different body areas should be packaged separately
    3. Combed hairs should be collected first and packaged separately
    4. Submit hair samples in sealed envelope or paperfold and label. Include the date of collection

Fiber Evidence

A fiber is the smallest unit of a textile material that has a length many times greater than its diameter. They can naturally occur, such as plant and animal fibers or can be man-made. Fibers can be exchanged between two individuals, an individual and an object, and two objects. When fibers match with a specific source, a value is placed on that association. This is dependent on many factors which include type and color of the fiber and number of different fibers found at the crime scene or on the victim.

The transfer of fibers may either be direct or indirect. A direct or primary transfer happens when a fiber is transferred from a fabric directly onto a victim’s clothing. Meanwhile, an indirect or a secondary transfer happens when an already transferred fiber on the clothing of a suspect transferred to the clothing of a victim. Understanding the kinds of transfer and their mechanics as well as the composition, and condition of the fibers are necessary for reconstructing events of a crime.

Types of fibers:

    1. Natural – plant and animal fibers like wool, cotton or silk
    2. Synthetic – includes polyester and nylon
    3. Manufactured – contains natural materials that are reorganized to create fibers

Collection and Packaging of Fiber Samples

    1. Submit the entire garment or textile if possible
    2. Submit fibers in sealed envelope or paperfold
    3. Photographs, casts, or lifts of fabric impressions may be submitted when the evidence cannot be submitted

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It is a capital mistake to theorize before you have all the evidence. It Biases the Judgement

Sherlock Holmes