The procedure used by the hair inspector should incorporate the general guidelines discussed in this file. Evidence handling and the correct use of equipment should be consistent with Scientific Working Group on Materials Analysis guidelines. Blood or debris on a hair sample may be significant. If the adhering material is of evidential importance, the examiner should consider removing and preserving it for possible future analysis. In a situation when the adhering material is not of evidential value, the hair may be washed or cleaned prior to mounting. The presence of a small amount of blood or debris on a hair may not interfere with the microscopical examination. A washed hair should be allowed to air dry prior to mounting. DNA analysis can be performed on hair but should be performed only after an initial microscopical assessment. A full and detailed microscopical evaluation with possible known sources of hair should be done prior to DNA analysis. Microscopical comparisons cannot always be done after DNA analysis, which is destructive to at least a portion of the hair. DNA analysis should always be considered in those cases when the source of a hair is crucial to an investigation. Hair exhibiting thermal or mechanical damage may be more brittle and should be handled minimally and with more care. Hair examinations and comparisons, as generally conducted by forensic scientists, often provide important investigative and associative information. Human and animal hairs have been used in forensic investigations for over a century. Reports abound in the literature concerning the use of human and animal hairs encountered in forensic casework. These guidelines represent a recommended procedure for the forensic examination, identification, and comparison of human hair. Hairs are readily available for transfer, easily transferred, and resilient. Hair examination may be used for associative and investigative purposes and to provide information for crime scene reconstruction. Frequently, hairs from the scalp and pubic regions of the body are used for microscopical comparisons. There is typically more interpersonal variability in the characteristics of scalp and pubic hairs than in the hairs from other body regions. Scalp hairs usually be evidence for more interpersonal variation than pubic hairs. Hairs from other body areas may also be compared, but these comparisons are usually less significant and less frequently conducted. Hence, these guidelines primarily reflect the considerations of human scalp and pubic hair comparisons. When retrieving evidence from a person’s head or pubic region, the combing technique can be used. Always use a new comb or brush. Lacing the teeth of a comb with clean cotton or gauze may help to retain hairs and debris on the comb. Place a piece of clean paper under the area that is combed to catch loose hairs and debris. This paper should be included in the evidence package with the comb. Hairs that are embedded in or adhering to a person or object must be carefully inspected before removal. If appropriate, the location of these hairs should be carefully documented. Care must be taken not to contaminate, crush, or break the hairs. Loose hairs should be collected from an object by picking them off individually. The remaining hairs can be collected from clothing, bedding, or other large surfaces by adhesive lifts. Be aware that the adhesive from the lifting material could interfere with the analysis of surface treatments that might be present on the hairs. Hairs can also be collected from an item by scraping or vacuuming. These techniques are described in the Trace Evidence Recovery Guidelines. Collect known hairs from specific somatic regions of related people for comparisons to questioned hairs. Every effort should be made to see that these hairs are collected as soon as possible relative to the occurrence. Full length hairs with roots should be obtained for the examiner to examine and compare hairs. Because the majority of pulled hairs will likely be in an active growing stage, a separate combing procedure can be used to obtain hairs in the telogen stage. A combing procedure for known hairs can be done after the combing for foreign hairs. The regions being sampled should be repeatedly combed or brushed over a large sheet of clean paper. It is desirable to package the pulled known hairs and combed known hairs separately. Known samples may be requested from all persons who might reasonably be considered a source of a questioned hair. If such samples are obtained and excluded as the source of the questioned hair, the significance of any ensuing association is increased. A stereomicroscope with a magnification range up to 100X is useful for the initial examination of mounted and unmounted hairs. A high-quality transmitted light microscope is necessary to examine and identify the microscopical characteristics of hairs. The objectives and eyepieces should permit observations in the range of approximately 40X to 400X. A polarized light microscope may enhance the hair examiner’s ability to see certain features and determine the cross-sectional shapes of the hairs. The use of a high-quality transmitted light comparison microscope is mandatory when comparing the microscopical characteristics of hairs. High-quality objectives are important, but highly corrected planapochromats are not necessary. The objectives and eyepieces selected, however, should permit observations in the range of approximately 40X to 400X. A high-intensity tungsten light source, suitable for photomicrography and equipped with a daylight correction filter, provides adequate lighting. Both sides of a comparison microscope should be balanced for light intensity and color. A comparison microscope may be equipped with one of several types of stages.The hair examiner should be familiar with the instruction manual and the manufacturer’s maintenance recommendations for each microscope used in hair examination. To ensure the precision, reliability, and performance of the polarized light and comparison microscopes, the following procedures for the maintenance of the microscopes should be performed on a routine basis.

Original Text:

http://www.fbi.gov/hq/lab/fsc/backissu/april2005/standards/2005_04_standards02.htm