Academic journal article Forensic Science Communications

Forensic Human Hair Examination Guidelines: Scientific Working Group on Materials Analysis (SWGMAT)

Academic journal article Forensic Science Communications

Forensic Human Hair Examination Guidelines: Scientific Working Group on Materials Analysis (SWGMAT)

Article excerpt

1. Introduction

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.

The ability to perform a forensic microscopical hair comparison is dependent on a number of factors. These factors include the following:

* Whether an appropriate known hair sample is representative.

* The range of features exhibited by the known hairs.

* The condition of the questioned hair.

* The training and experience of the hair examiner.

* The usage of the appropriate equipment and methodology.

DNA analysis can be performed on hair but should be performed only after an initial microscopical assessment. A full and detailed microscopical comparison 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.

2. Referenced Documents

2.1. Scientific Working Group on Materials Analysis. Trace evidence quality assurance guidelines, Forensic Science Communications [Online]. (January 2000). Available: www.fbi.gov/hq/lab/fsc/backissu/jan2000/swgmat.htm.

2.2. Scientific Working Group on Materials Analysis. Trace evidence recovery guidelines, Forensic Science Communications [Online]. (October 1999). Available: www.fbi.gov/hq/lab/fsc/backissu/oct1999/trace.htm.

3. Terminology

The terms in this section are defined by how they are used in forensic hair examinations.

Amorphous medulla is a medulla that has no distinct form, pattern, or shape when viewed with a transmitted light microscope.

Anagen is the active growth phase of a hair follicle in the hair growth cycle. The root from a pulled anagen hair is elongated, may be covered with a root sheath, and is usually fully pigmented.

Association is the determination that two or more hairs could share a common origin.

Bleaching is a chemical or a natural process used to make a hair colorless or lighter than its usual color.

Buckling is an abrupt change in the shape and orientation of a hair shaft with or without a slight twist, often seen in pubic hairs.

Catagen is the transitional phase of the hair follicle from the active growth phase (anagen) to the resting growth phase (telogen) in the hair growth cycle.

Caucasoid is an anthropological term designating one of the major groups of human beings originating from Europe and originating from the Indian subcontinent.

Characteristic is a microscopic or macroscopic feature or attribute of a hair.

Color is the aspect of objects that may be described in terms of hue, lightness, and saturation. It should be recognized that the macroscopical and microscopical colors of hairs might appear different.

Comparison is the examination of two or more hairs to evaluate whether or not they could have come from the same source.

Continuous medulla is a medullary appearance showing no disruptions along the shaft of the hair.

Convolution is a rotation or twisting of the hair shaft that can occur naturally, from disease, or as a result of mechanical force.

Cortex is the primary anatomical region of a hair between the cuticle region and the medullary region composed of elongated and fusiform cells. …

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