The History of Hair and Fiber Analysis
One of the first reports on Trichology, the scientific study of human hair, was published in France in 1857. This report introduced the importance of examining hair during a criminal investigation. Microscopic examination of hair was conducted in the early 20th century and enabled the rapid expansion of the field.
In 1931, Professor John Glaister published a book, Hairs of Mammalia from the Medico-legal Aspect, that became a popular resource for hair information, but it was John Hick's 1977 book, Microscopy of Hairs: A Practical Guide and Manual, that laid the groundwork for the use of hair evidence by forensic examiners.
Characteristics of Hair and Fibers
There are three layers to hair: the medulla, the cortex, and the cuticle.
Forensic investigators must first determine whether a hair came from a human or an animal by looking at the basic structure of the hair. Some animal hair looks a lot like human hair, so certain characteristics of the hair are noted. Human hair usually has even coloration and pigmentation throughout its length, whereas animal hair often has banding, which is drastic color variations. Another characteristic of animal hair is the variation in the root structure. Human hair has a club shaped root almost 100% of the time.
Human head hairs may also indicate racial origin. Certain properties of the hairs allow them to be classified as Caucasian, Negroid, or Mongoloid (European, African or Asian). Mixed race individuals do not usually show these identifying characteristics.
Fibers from clothing, upholstery, carpeting, and bedding, also have certain characteristics that can be studied under a microscope and used as forensic evidence.
Forensic Methods
Law enforcement has various methods for gathering hair and fiber samples. Picking, shaking, taping, and scraping are some of the methods used to gather hairs and fibers from bedding and clothing. Specially filtered vacuums may be used to gather hair from carpeting and upholstered surfaces. Hairs are often gathered with tweezers and combs, stored in bags, and carefully transported to the storage facility in order to prevent contamination of the sample.
Microscopes are used to analyze the hair and fiber specimens in the laboratory. The traditional microscope used is a comparison microscope, constructed from two compound microscopes, and allows the identification of color, texture, shape pattern, twist, and cross-sectional appearance. The root of the hair is also examined for evidence of how the hair was removed from the body (forcibly or not).
One of the first reports on Trichology, the scientific study of human hair, was published in France in 1857. This report introduced the importance of examining hair during a criminal investigation. Microscopic examination of hair was conducted in the early 20th century and enabled the rapid expansion of the field.
In 1931, Professor John Glaister published a book, Hairs of Mammalia from the Medico-legal Aspect, that became a popular resource for hair information, but it was John Hick's 1977 book, Microscopy of Hairs: A Practical Guide and Manual, that laid the groundwork for the use of hair evidence by forensic examiners.
Characteristics of Hair and Fibers
 |
| Human Hair |
 |
| Dog Hair |
There are three layers to hair: the medulla, the cortex, and the cuticle.
Forensic investigators must first determine whether a hair came from a human or an animal by looking at the basic structure of the hair. Some animal hair looks a lot like human hair, so certain characteristics of the hair are noted. Human hair usually has even coloration and pigmentation throughout its length, whereas animal hair often has banding, which is drastic color variations. Another characteristic of animal hair is the variation in the root structure. Human hair has a club shaped root almost 100% of the time.
Human head hairs may also indicate racial origin. Certain properties of the hairs allow them to be classified as Caucasian, Negroid, or Mongoloid (European, African or Asian). Mixed race individuals do not usually show these identifying characteristics.
 |
| Caucasian Hair |
 |
| Mongoloid Hair |
 |
| Negroid Hair |
Fibers from clothing, upholstery, carpeting, and bedding, also have certain characteristics that can be studied under a microscope and used as forensic evidence.
 |
| Nylon fiber |
 |
| Wool fiber |
Law enforcement has various methods for gathering hair and fiber samples. Picking, shaking, taping, and scraping are some of the methods used to gather hairs and fibers from bedding and clothing. Specially filtered vacuums may be used to gather hair from carpeting and upholstered surfaces. Hairs are often gathered with tweezers and combs, stored in bags, and carefully transported to the storage facility in order to prevent contamination of the sample.
Microscopes are used to analyze the hair and fiber specimens in the laboratory. The traditional microscope used is a comparison microscope, constructed from two compound microscopes, and allows the identification of color, texture, shape pattern, twist, and cross-sectional appearance. The root of the hair is also examined for evidence of how the hair was removed from the body (forcibly or not).
Good balance of text and pictures, make sure to site your sources though.
ReplyDelete