Forensic Microscopy

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Forensic Microscopy

• Microscope 1

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Forensic Microscopy

• Generally takes one of six forms depending on the
  type of evidence to be examined
• Compound microscope
• Stereoscopic microscope
• Comparison microscope
• Polarizing microscope
• Microspectrophotometer
• Electron microscope

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Compound Microscopes

• The classic microscope
• Light is passed through object from beneath
• Image is upside down and backwards
• May possess a zoom magnification or multiple
  lenses of varying strength
• Monocular and binocular versions
• Generally up to 1000x magnification
• Higher magnification limitations
• Depth of focus is decreased and creates
  focusing challenge
• Cuts down on available light

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Compound Microscopes

• Major Components
• Eyepiece
• Tube
• Nosepiece
• Objectives
• Stage
• Focus
• Arm
• Base

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Compound Microscopes
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Comparison Microscopes

• Essentially two compound or stereographic
  microscopes joined by a bridge
• Vital for side by side comparison of two pieces
  of evidence
• View can show either microscope or can be split
  to show both at the same time
• Especially useful in ballistics and hair/fiber
  cases

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Comparison Microscopes
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Stereographic Microscopes

• Most frequently used type of microscope in
  forensics
• Light is passed either through an object or from
  above
• Image is projected right side up and correct
  right to left
• Usually the only method for opaque forms of
  evidence
• Especially useful for soil analysis, entomology
  and macroscopic evidence
• Magnification generally ranges from 2x to 125x
• Often called dissecting microscopes

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Stereographic Microscopes
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Polarizing Microscopes

• A special microscope application that outfits a
  normal microscope with two devices (a polarizer
  and an analyzer)
• The polarizer is used to impact incoming light
  waves to reveal special properties of a material
• Affected light waves then pass through analyzer
  before hitting the eye
• Especially useful in soil analysis (minerals) and
  the identification of artificial fibers

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Polarizing Microscopes
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Polarizing Microscopes
Blemish on an LCD screen visible in polarized
light (right) but not in normal visible light
(left)
Polarizing microscope view a a thin slice of
granite
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Electron Microscope

• Unique in that it uses a beam of electrons aimed
  at the object
• Does not use light
• Extremely high magnification possible
• Ranging from 10x 100,000x
• Can also be used as a spectroscope in some
  applications
• Useful in gunshot residue cases
• Very expensive

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Electron Microscope
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Electron Microscope
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Electron microscope
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Electron microscope
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Microspectrophotometer

• A beam of light is aimed at the object and its
  spectrum can be collected
• The specific spectrum will be unique to
  particular chemicals, fibers, etc.
• Spectral fingerprints can then be used to
  determine specific matches between different
  evidence samples

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Microspectrophotometer
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Microspectrophotometer