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17  Forensic Science Powerpoint Chapter 17 Microanalysis Of Exam
 

17 Forensic Science Powerpoint Chapter 17 Microanalysis Of Exam

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    17  Forensic Science Powerpoint Chapter 17 Microanalysis Of Exam 17 Forensic Science Powerpoint Chapter 17 Microanalysis Of Exam Presentation Transcript

    • Forensic Science An Introduction to Scientific and Investigative Techniques Stuart H. James and Jon J. Nordby Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Chapter 17
      • Microanalysis and Examination of Trace Evidence
      • Chapter Authors: Thomas A. Kubic and Nicholas Petraco
      • Presentation created by Greg Galardi, Peru, Nebraska
      • Edited by Stuart H. James, Fort Lauderdale, Florida and
      • Dan Mabel, Richmond, Virginia
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Microanalysis
      • Microanalysis is the application of a microscope and microscopical techniques to the observation, collection, and analysis of microevidence that can not be clearly observed or analyzed without such devices
      • Deals with samples in milligram or microgram size ranges
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Trace Evidence
      • Trace evidence - qualitative or quantitative analysis of the minor or ultraminor components of a sample
      • Sample – entire submitted exhibit or a subsample of the exhibit
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Forensic Laboratories
      • Large forensic laboratories are generally more specific: fiber, hair, mineralogy, paint, serology, firearms analyses, controlled substances
      • Small laboratories may be grouped differently, such as in sections of chemistry, biology, microscopy, drugs and ballistics
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Instruments of Microanalysis and Sample Types
      • Microscopes are the first tool used to examine trace evidence
      • Stereo binocular microscopes, compound in nature, are often used
      • Lens – optical component that may be composed of one or several elements
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Instruments of Microanalysis and Sample Types
      • Stereo microscopes have two separate eyepieces, and views are separated by a small angle (15 degrees)
      • Use of stereo microscopes allows for item being examined to been seen separately by each eye. This creates the appearance of three-dimensions.
      • Stereo microscopes are normally used with reflected light
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    •  
    • Instruments of Microanalysis and Sample Types
      • Compound binocular microscope – second most common type of microscope encountered in laboratory
      • Two eyepieces are present, however, both eyes see the same image
      • This microscope often employs transmitted, bright field illumination
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    •  
    • Terminology of a Microscope
      • Objective (OBJ)
      • Eyepiece (EP)
      • Magnification (x) – amount subject is enlarged by lens system, the objective, eyepiece or other
      • Working Distance (WD) – distance between the subject and the closest portion of the objective when focused
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Terminology of a Microscope
      • Depth of Field (DF) – total distance, height, above and below the point of focus that appears clearly focused
      • Angle of Acceptance (AA) – maximum angle between light waves that an OBJ can collect
      • Numerical Aperture (NA) - NA = N sin AA/2
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    •  
    • Terminology of a Microscope
      • Resolving Power (RP) - Ability to distinguish fine differences in structure
      • N - lowest refractive index (RI) material between the subject and the objective
      • Refractive Index (RI) – Velocity of a light in a vacuum divided by the velocity of light in the medium of interest
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Micrometry
      • A scale calibrated with a stage micrometer can be placed in the eyepiece of microscope to measure an items:
        • Length
        • Width
        • Thickness
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Other Alternative Uses of Microscopes
      • Chemical tests can be performed on micro or ultramicro samples under a microscope
      • Color and micro-crystal tests for identification of substances, or reactions to a solvent can be observed
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Light
      • Light is a wave phenomenon. Its characteristics include:
        • Velocity
        • Wavelength
        • Frequency
        • Amplitude
        • Vibration direction
        • Wavelength and frequency are inversely related
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Light
      • Can become partially or totally polarized by:
        • Reflection
        • Adsorption
        • Propagation through an anisotropic material
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Light
      • Normal light is randomly polarized, which means vibration direction of light is in all directions (360 directions)
      • Plane polarized light - vibration is only in one direction
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Polarized Light Microscope
      • Polarized Light Microscopes (PLMs) also may have an accessory slot in the intermediate accessory tube, which allows for placement of additional devices into optical path
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Polarized Light Microscope
      • Compound microscope fitted with certain accessories can be converted to a polarized light microscope (PLM)
      • Two polarizing elements:
        • Polarizer- placed in condenser mount prior to lens
        • Analyzer – usually positioned in body of microscope in intermediate accessory tube
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    •  
    • Polarized Light Microscope
      • Most analytical capability is the characteristic RIs of anisotropic materials
      • Materials are divided into uniaxial and biaxial classes
      • RIs of these materials are characteristic rather than universal unless certain parameters of measurement are controlled and stated
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Polarized Light Microscope
      • Instrument of choice to characterize many forms of microscopic materials
      • Can lead to clear, unambiguous identifications and can aid significantly in individualization and association
      • There are other microscopes that are used, comparison microscopes and macroscopes that are used
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Polarized Light Microscope
      • Most common accessories for accessory slot of a PLM are compensators
      • Compensator- anisotropic materials of known birefringence constructed so that thickness is controlled and orientations of vibration are known
      • Compensators can be fixed or variable, and measure retardation in nanometers
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Macroscopes
      • Lowest total magnifications are found on macroscopes: seldom rise above 60 diameters
      • Use reflected light to examine evidence
      • Very useful in identification of large tool marks, fabrics, and ballistic marks (stria) on cartridges
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    •  
    •  
    • Microspectrophotometry
      • Instruments that generate transmission, reflection, or adsorption spectra from various translucent or opaque samples
      • Principal types of instruments are visible and infrared
      • Commonly used to analyze colored fibers or paint surfaces
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    •  
    • Scanning Electron Microscope (SEM)
      • A microscope that permits viewing of samples at much greater magnification and resolution than is possible by light microscopes
      • Magnification is possible in the range of 10 to 100,000x
      • When combined with a energy dispersive x-ray spectrometer, (EDS) this tool becomes invaluable
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Scanning Electron Microscope
      • SEM/EDS combination can readily resolve a particle smaller than 1 micrometer in size, while generating spectra revealing elemental size of object
      • SEMs are more valuable due to development of low pressure or low vacuum systems which allow sample being studied not to be kept at such great reductions in pressure
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    •  
    •  
    •  
    • Other Instrumental Techniques of Value to a Microanalyst
      • X-Ray diffraction
      • Pyrolysis Gas Chromatography/Mass spectrometry
      • X-ray fluorescence
      • Atomic absorption
      • Atomic emission
      • Atomic Mass Spectrometry
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Microscopic Evidence and its Analysis - Glass
      • Glass is a common type of evidence
      • Commonly encountered as transfer evidence
      • Examination of broken glass can reveal whether the impact that caused the fracture was caused by low or high velocity blunt trauma (Coring Effect)
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    •  
    • Microscopic Evidence and its Analysis - Glass
      • Radial crack – those cracks originating from impact point and propagating away
      • Concentric crack- those cracks seeming to make a circle around the point of impact
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    •  
    • Microscopic Evidence and its Analysis - Glass
      • Conchoidal lines – those edge characteristics of glass fractures. They are stress marks shaped like arches that are perpendicular to one glass surface and curved nearly parallel to the opposite surface. The perpendicular surface faces the side where the crack originated
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    •  
    • Microscopic Evidence and its Analysis - Glass
      • When microscopic glass chips are examined, the following properties are evaluated:
        • Physical – thickness, uniformity, color, curvature, surface conditions-tinting, soiling, etc
        • Optical – most significant property is Refractive Index
        • Elemental – composition of glass
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    •  
    • Microscopic Evidence and its Analysis - Glass
      • In order to determine whether liquid medium or solid sample has a higher refractive index, three methods are commonly used:
        • Oblique Illumination
        • Dispersion staining color
        • Movement of Becke line
      • However, better accuracy is required for advanced criminalistics work
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    •  
    •  
    • Microscopic Evidence and its Analysis – Hairs and Furs
      • Hairs and furs are natural fibers of animal origin
      • Hair examiners can often conclusively eliminate a person as a source of hair
      • However, rarely can the examiner absolutely associate a hair to a person
      • Hairs are generally grouped by racial origin and body location
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Microscopic Evidence and its Analysis – Hairs and Furs
      • Furs can generally be classified by species with a microscope
      • Subclassification of fur is difficult without an extensive reference collection
      • Basic characteristics of color, length and curliness may be valuable
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Microscopic Evidence and its Analysis – Hair and Fur
      • Hair and Fur are composed of keratin, melanin and trace metals
      • Structure of hair :
      • Cuticle- outermost portion of hair
      • Cortex – contains cortical fusi and ovoid bodies and is between medulla and cuticle
      • Medulla- center portion
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Microscopic Evidence and its Analysis – Hair and Fur
      • Parts of hair or fur:
        • Proximal end - Root portion or bulb
        • Distal end - Tip of hair
        • Anagen Stage- Period of growth of hair
        • Catagen Stage – Transition phase
        • Telogen Stage – dormant or sloughing stage
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    •  
    • Microscopic Evidence and its Analysis – Hair and Fur
      • Racial origin of hair can be determined and classified as Caucasian, Negroid or Mongoloid
      • Scales cover the shaft of the hair and point away from proximal end to distal end.
      • The scale structures are normally divided into three different types.
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Microscopic Evidence and its Analysis – Hair and Fur
      • Types of scales are:
        • Petal – triangular or protrude from shaft and usually found on cats, seals, minks
        • Imbricate – flattened scales, like shingles on a roof and generally found on humans
        • Mosaic -resemble stacks of paper cups and found on small rodents and bats, rarely humans
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Three types of cuticles found in hair
    • Three types of medullas found in hairs and furs of animals
    • Microscopic Evidence and its Analysis – Hair and Fur
      • Hair can be determined from any location: head, pubic area, limb, beard chest, pubic, axillary or other areas.
      • Trace metal comparison in hairs has met with limited success
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Microscopic Evidence and its Analysis – Fibers
      • Fibers are a common class of microscopic evidence.
      • They have numerous major classifications and generic subtypes, are physically different, are processed many ways, transfer easily, have significant persistence and thus are valuable forensic evidence.
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Microscopic Evidence and its Analysis – Fibers
      • Fibers may be grouped as animal, vegetable, or mineral
      • Also categorized as naturally occurring, manufactured, and synthetic
      • Use of microscopy for initial examination and collection of first analytical data is accepted forensic procedure
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Microscopic Evidence and its Analysis – Fibers
      • Fiber is analyzed under microscope and the following are documented:
        • Size, Crimp, Color ,Luster, Possible cross section, Damage, Soil and Adhering debris
      • Initial examination is followed by examination with a polarizing light
      • microscope
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    •  
    • Microscopic Evidence and its Analysis – Fibers
      • Examination of fibers is carried out under crossed polars and with plane polarized light
      • Fiber is determined to be isotropic or anisotropic
      • Almost all isotropic fibers are from glass
      • SEM/EDS allow determination of elemental composition of fiber
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    •  
    • Microscopic Evidence and its Analysis – Paint
      • Paint samples are a major portion of microsamples submitted to laboratories
      • Paint samples usually involve paint transfer and vehicular accidents
      • Paint transfer from architectural sources- crimes against property are submitted occasionally
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Microscopic Evidence and its Analysis – Paint
      • Paint is composed of:
        • Binders which hold all components together and is of a polymeric nature, consisting of natural or synthetic resins
        • Pigments which supply paint color
        • Extenders are added to paint to increase its solid content and its opacity and hiding ability
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Microscopic Evidence and its Analysis – Paint
      • Modifiers are added to paint formulations and affect paint film’s durability, gloss, flexibility, hardness, resistance to ultraviolet radiation, and other characteristics
      • Paint films can be investigated according to a number of physical and chemical characteristics
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Microscopic Evidence and its Analysis –Paint
      • When paint is to be analyzed, it is best to submit entire object to laboratory
      • When this is impractical, paint must be removed from object and submitted
      • Collect sample from area close to the alleged contact and any other additional samples
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Microscopic Evidence and its Analysis –Paint
      • First part of paint examination is the goal of obtaining a physical match
      • Fit of jigsaw edges or match of surface striae questioned is strong evidence
      • If physical match is not obtained, layer structure order, color, thickness, and other details should be documented
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Microscopic Evidence and its Analysis –Paint
      • Angle cuts and thin sectioning with a scalpel also can reveal layer structure
      • Chemical reactions can also serve as sources of data
      • Fluorescence microscopy, Infrared microspectrophotometry and recently available Raman microspectrometers are all other options for analyzing paint
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Microscopic Evidence and its Analysis –Paint
      • SEM/EDS, x-ray diffraction, x-ray fluorescence, pyrolysis with gas chromatography also may be used
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Microscopic Evidence and its Analysis- Soils
      • PLMs are excellent tools for soil analysis
      • Soils are separated, then the minerals are identified by color, shape, and optical properties
      • Mineral content of soil assists in indicators of location of soil sample
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Microscopic Evidence and its Analysis – Gunshot Residue
      • Gunshot Residue (GSR) is a mixture of organic and inorganic materials originating from the projectile, cartridge case, propellant, and primer that emerge from the barrel and openings of the firearms
      • Determination of GSR is to confirm residue is indeed GSR
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    • Microscopic Evidence and its Analysis – Gunshot Residue
      • Methods to analyze gunshot residue include Instrumental neutron activation analysis, graphite furnace atomic absorption, and inductively coupled atomic emission spectroscopy
      • Sample is considered when certain elements, normally barium and antimony, are found together above a baseline level
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    •  
    • Microscopic Evidence and its Analysis – Gunshot Residue
      • SEM/EDS can be used to analyze possible gunshot residue
      • Consideration in collection of gunshot residue and analysis should include possible environmental contamination, location of sample, and where sample was collected – web of hand, palm, other parts of the body, etc
      Chapter 17 CRC Press: Forensic Science, James and Nordby, 3rd Edition
    •