【国外标准】 Standard Guide for Forensic Examination of Hair by Microscopy

4.1 A microscopical hair examination is conducted to determine if the item is a hair; from a human; from a particular somatic region; characteristic of a broad geographically-assigned ancestral group; characteristic of a particular growth phase; damaged; symptomatic of disease, condition, or disorder; forcibly removed; chemically altered (for example, dyed or bleached); suitable for microscopical comparison; suitable for DNA analysis; and similar to or different from a known sample (4-9).4.2 Most often, hairs from the head and pubic regions of the body are used for microscopical comparisons. There is usually more interpersonal variability in the characteristics of head and pubic hairs than in the hairs from other somatic regions. Head hairs usually show more interpersonal variation than pubic hairs. Hairs from other somatic regions may also be compared, but these comparisons are usually limited and less frequently conducted. Accordingly, this guide primarily considers human head and pubic hair comparisons.4.3 Microscopical hair comparisons are not a means of individualization (10). This limitation is to be stated in any communication (for example, reports, testimony) when an association is reported.4.4 Additional analyses can be performed on hairs that have been chemically altered (for example, dyed hair) or have trace materials on the surface (for example, glitter). Such techniques are beyond the scope of this document.1.1 This guide covers procedures used by forensic laboratory personnel in the forensic examination of hair by microscopy, including microscopical comparisons and classification of hair samples.1.2 This guide addresses instrument setup, hair collection, sample handling techniques, and the use of various microscopes in the examination and comparison of hair.1.3 This guide addresses the benefit of following microscopical examinations with DNA analysis.1.4 This standard is intended for use by competent forensic science practitioners with the requisite formal education, discipline-specific training (see Practice E2917), and demonstrated proficiency to perform forensic casework.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.