HAIRS AND FIBERS
This unit describes the importance of two of the most commonly encountered types of trace evidence in the crime laboratory and how forensic scientists examine, identify and compare these types of evidence in order to help establish a link between the criminal and their victims or to the crime scene.
Chapter 11: “Hairs and Fibers”
In Chapter 11, you will learn that trace evidence in the form of hairs and fibers, that is transferred between people and objects during the commission of a crime will, if recovered, offer corroborative evidence developed by investigators during the course of an investigation. You will also learn that, although in most cases hair and fiber evidence may not provide a positive identification of a suspect, laboratory examination may narrow the origin of such evidence to a group that includes the suspect.
Using microscopes described in unit 8 along with other forensic techniques, forensic scientists have developed a variety of procedures for the identification and comparison of hair and fiber evidence. Advances in DNA analysis procedures have led to its use to complement and support traditional microscopical hair comparison techniques.
Fibers: Fibers are a common type of trace evidence that originate from a variety of different sources such as the textiles found in clothing, carpeting, rope, thread, and furniture upholstery. Some types of fibers are natural and can be of botanical, animal, or mineral origin. Examples of mineral based fibers include asbestos and other fibrous insulation materials. There are also a variety of manufactured fibers that have been developed over the past century. Fibers can become important evidence in crimes that involve personal contact (homicide, sexual assault, and other violent crimes). Cross transfers of fibers that occur between the suspect and the victim can become significant associative evidence.
Follicle: An organ below the surface of the skin in which a hair is anchored and grows out of.
Hair: A slender threadlike outgrowth from the follicles of the skin of mammals.
Mitochondrial DNA (mtDNA): DNA found outside the cell nucleus in the mitochondria, the power plants of the cell, providing about 90% of the energy that the body needs to function. mtDNA is found in much greater abundance in a cell than nuclear DNA, thus providing DNA profiles on very small or degraded samples containing a limited quantity of nuclear DNA. This type of DNA is maternally inherited, thus all children of a biological mother have the same mtDNA and all of the daughters of those children will have children with the same mtDNA and so forth throughout a family lineage.
Nuclear DNA: This form of DNA is inherited in equal parts from the mother and father and is found exclusively in the cell nucleus.
Polymer: A substance composed of a large number of atoms. These atoms are usually arranged in repeating units or monomers. There are naturally occurring polymers such as cotton and man-made polymers such as polyester and other plastics. Both can become important trace evidence in a criminal investigation.
A suspect was apprehended after an attempted sexual assault was reported to the police.
The victim wore a green sweatshirt manufactured with a blend of cotton and polyester fibers. The suspect wore a blue sweater manufactured with a blend of wool and acrylic fibers.
The suspect’s clothing and the victim’s sweater were submitted to the crime lab for forensic fiber analysis.
In a 3-5 page essay discuss how forensic scientists conduct forensic examination of fibers.
Define the basic types of textile fibers.
Differentiate between the different types of microscopes available to the forensic scientist conducting forensic fiber examinations. (An excellent answer would include at least five major points.)
Discuss how the crime lab would identify and compare the fiber evidence from the attempted sexual assault. (An excellent answer would include at least five major points.)
Evaluate the proper methods of collecting and preserving fiber evidence.
Use the course text and at least two outside research sources including academic journals to support your view.
Format consistent with APA guidelines.
In addition to fulfilling the specifics of the assignment, a successful paper must also meet the following criteria:
Include a cover page and references page in 10 – 12 point font (Arial, Courier, and Times New Roman are acceptable)
Viewpoint and purpose should be clearly established and sustained
Assignment should follow the conventions of Standard English (correct grammar, punctuation, etc.)
Writing should be well ordered, logical and unified, as well as original and insightful
Your work should display superior content, organization, style, and mechanics
Appropriate citation style should be followed
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Include a title page with full name, class name, section number, and date
Include an introductory and concluding paragraph and demonstrate college-level communication through the composition of original materials in Standard English
Use examples to support your discussion
Cite all sources on a separate reference page at the end of your paper and cite within the body of your paper using APA format and citation style. For more information on APA guidelines, visit Academic Tools.