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Optical Microscopy in Forensic Science

Forensic Science

  1. Lori J. Wilson,
  2. Barbara P. Wheeler

Published Online: 15 DEC 2009

DOI: 10.1002/9780470027318.a9101

Encyclopedia of Analytical Chemistry

Encyclopedia of Analytical Chemistry

How to Cite

Wilson, L. J. and Wheeler, B. P. 2009. Optical Microscopy in Forensic Science. Encyclopedia of Analytical Chemistry. .

Author Information

  1. Eastern Kentucky University, Richmond, KY, USA

Publication History

  1. Published Online: 15 DEC 2009

Abstract

The microscope maintains a prominent position as an important tool for examination of trace amounts of evidence. The microscope is used by forensic scientists to locate, isolate, identify, and compare samples. Because of its low magnification, wide field of view, large working distance, and stereoscopic vision, the stereomicroscope is used for preliminary evidence evaluations. It also allows for comparative examinations for evidence such as paint, physical matches, questioned documents, and impression evidence. While the main advantage of the polarizing light microscope (PLM) is its use in the identification of samples, it is also used for comparison. The PLM offers higher magnification and provides information on the morphological, optical, chemical, and physical properties of the sample. Morphological properties are often used to identify and compare fibrous evidence such as human and animal hair as well as man-made and natural fibers. Optical properties such as refractive index, birefringence, pleochroism, and interference figures are combined with morphological properties to compare and identify forensic samples. Particle identification and microcrystalline testing can be used to determine the chemical properties of various types of evidence. Finally, physical properties such as color, solubility, melting point, and boiling points can also be used to identify and compare forensic samples.

Keywords:

  • stereomicroscope;
  • polarizing light microscope;
  • physical match;
  • paint;
  • impression evidence;
  • drug;
  • questioned document;
  • glass;
  • fiber;
  • soil;
  • hair;
  • birefringence;
  • refractive index;
  • anisotropic;
  • isotropic