HAIRS AND FIBERS

The value of hairs and fibers as evidence in criminal cases has been clearly recognized. Hairs and fibers are seldom conclusive as evidence but, in conjunction with other details, have proved to be important and essential aids. You must capitalize on the importance of this type of evidence during the initial phase of the investigation.

The origin and texture of hairs and fibers found at the crime scene or on the body, clothing, or headgear of a suspect or victim, may be exceedingly important as evidence, particularly in assaults and sex crimes. Hairs may be pulled out during the crimes and found at the scene or on the victim. Hair and fiber transfer may occur during any physical contact between the suspect and the victim. Hair may fall out under conditions that the suspect is not aware of and unable to guard against. Properly handled, hair and fibers may provide excellent investigative leads and add to the evidentiary facts being assembled.

Hair

Structurally, a hair is composed of the tip end, cuticle, cortex, medulla, and bulb or root (see fig. 16-13). Each of these provides the laboratory examiner with definite information.

The cuticle is the outer surface of the hair and, when seen under the microscope, appears composed of scalelike flakes, each overlapping the other similar to the overlapping of shingles on a roof or scales on a fish. These scales are known as cuticular scales.

The cortex is the inner portion of the hair and contains the pigmentation or coloring of the hair.

The medulla may be described as the core or center portion of the hair shaft and, under magnification, appears as irregular, spinal, chain, or a continuous dark line of varying width, running up the center of the hair shaft.

Examination of any or all three of these sections may reveal any one of a number of personal characteristics of its sources. Important information may be gained through visual, microscopic, and chemical examinations of the root a bulb of the hair, the shaft, and the tip.

Figure 16-13.-Shaft of hair.

Hair Examination

Through examination, a laboratory will normally first determine if the hair samples are of animal or ^{human origin.} If the hairs are animal, a general determination as to species may be made, such as cat, dog, horse, or cow.

In the case of human hairs, laboratory determinations may include the following: 

. Race of the person from whom the hair originated (Black Mongolian, or Caucasian). 

l Area of the body surface from which the hair originated (head, face, chest, armpit, limb, or pubic area). 

l How the hair was removed (naturally or forcibly). 

. How the hair had been treated (bleached, dyed, waved).

. Whether the hair was cut with a dull or sharp instrument; recency of cutting; crushed or burned.

. Blood grouping, sex, and age may be estimated or determined.

Laboratory hair comparison conclusions generally will be stated in one of three forms, as follows:

1. Hairs are dissimilar and did not originate from the same individuals.

2. Hairs match in terms of microscopic characteristics, and blood groupings, and originated either from the same individual or another individual whose hair exhibits the same microscopic characteristics.

3. No conclusion could be reached.

Fibers

Contact between two pieces of fabric seldom can be made without an interchange of fiber material. In cases involving physical contact, both the victim's and suspect's clothing may intermingle and exchange fibers. In burglary cases, contacts of citing with objects should also be considered in the examination of the crime scene and suspect's clothing for fiber evidence. Points of entry, such as windows, or means of access to roofs, ladders, or drain pipes may reveal fiber traces of value to the investigation. Clothing fibers and fibers from the upholstery of automobiles may also be transferred from one to the other.

Fibers generally are classified as mineral (glass asbestos), vegetable (cotton, linen, hemp, jute), synthetic (rayon, nylon, orlon), or animal (wool, silk furs). Classifications vary greatly as to color and type of processing, yarn and thread composition, and end use. Fabrics, tapes, ropes, and similar end products may be subjected to fiber examination and instrumental analysis.

Fiber Examination

Fabric, which is composed of knotted or woven yarns (fibers twisted together), will be grossly examined in terms of color, composition, and construction. Questioned fabrics may be determined to be similar to known fabrics. Positive identification may be made when a questioned piece of fabric may be fitted back into the known fabrics. This type of fabric examination is based on matching broken ends of yarn together.

Fibers will be identified as to type, color, and matching characteristics based on microscopic, microchemical, and melting-point examinations.

Generally, fiber matches are not positive evidence and require substantiation with other corroborative evidence.

Tape examination, similar to fabric examination generally involves matching ends of pieces of tape used at the scene of a crime with the end of tape on a roll found in the possession of a suspect.

Cordage, in the form of ropes and strings, is examined in terms of composition, color, diameter, and construction. The known is compared with the unknown, and occasionally ends may be matched or the manufacturer determined

Handling and Transmittal

The most difficult task is to initially locate hair and fiber evidence at the scene of the crime. The search must be thorough. Obvious places to search are headgear and clothing, with particular attention being given to linings, pockets, and cuffs. Besides searching the general crime scene area, other areas to search may include the victim's body, underneath the fingernails, and any upholstered surfaces.

Of supreme importance is the basic rule: Avoid contamination of evidence.

Hair and fiber evidence is particularly susceptible to cross contamination, and you must ensure that evidence gathered from the suspect and from the victim is not intermingled. It must be individually collected, properly marked, placed on a clean piece of paper (which is folded and put in a clean container), and properly separated cluing packing for transmittal.

Detailed examination of hair and fibers should be left to the laboratory.

When collecting known samples from the victim or suspect, gather a sufficient quantity. Twenty hairs or fabric strands are considered the minimum.

Only a doctor should collect sample hairs from the body of a victim or subject. These samples should be obtained from the various parts of the body possibly involved in the crime. Hair combings and representative samples of cut or pulled hairs should be submitted

Envelopes sealed around all edges, plastic bags, or pillboxes should be used as containers for hairs and fibers. The use of tape or glue to hold the hairs or fibers on a surface will interfere with laboratory examination.