Hair and fiber analysis

In forensics, the analysis of hair or fiber evidence found at a crime scene can often be very useful in linking a suspect or victim to a scene. Use of hair and fiber evidence in forensics was already well established by the early twentieth century, and was and is an important tool in any investigation. Hair and fiber evidence alone is typically not enough to make a conviction, but is nevertheless a useful asset in crime solving.

One of the first scientific papers on hair and/or fiber analysis was published in 1857. By the early twentieth century, the microscopic examination of hair and fabric fibers was firmly established in forensics.

Hair can be very useful in the identification of a suspect or victim. In humans, hair can be used to identify the race of a person, to general classifications of the Negroid, Mongoloid and Caucasian races. Aspects of a hair such as color, texture, width, and the shape of the root can be used to tell whether the hair originated from a human, it'sspecific race, or even matched to a particular individual.

A comparison of hairs of different races

Fibers can be collected from a scene in a number of ways. Sometimes it is possible to individually pick out a fiber, but this is not always the case. Many times it is more useful to use tools such as sticky tape or specialized vacuums to collect fibers from surfaces such as upholstery or other fabrics.

There are many types of fibers other then hair that could be used to aid an investigation. When a piece of fabric, such as a person's clothing, comes into contact with another object, it will typically leave small traces of the fiber it is constituted of. Cotton, wool, silk, hemp and many different varieties of synthetic fibers make up most clothing, and the fibers that said clothing sheds can be used to link persons of interest to a particular scene. Synthetic fibers such as nylon, rayon, or polyester are produced by extruding liquid which then cools and solidifies; as a result of this production method, the resulting fiber has a very smooth and even appearance when viewed under a microscope, similair to the natural fiber silk, whichis produced naturally in a similair way.

Various types of fibers as they appear under a microscope.

One particularly famous case in which fiber analysis was used to build a case was the case of the Atlanta child murders from 1979 through 1981. Police first identified Wayne Williams as a suspect in the case when a stakeout crew noticed him driving away from a bridge near which a loud splash had occurred, suggesting that he had dumped a body. The body of the 27 year old Nathaniel Carter was found two days later in the river, corroborating this theory. Police investigators discovered fibers on victims that matched with fibers from Williams' car, bedspread, carpets, and dog. Williams was convicted to two consecutive life sentences, and declared to be the culprit behind 23 of the 29 child murders that occurred in Atlanta from 1979 to 1981.