Chapter 16 CRC Press: Forensic Science, James and Nordby, 2nd Edition 1# Forensic Science An Introduction to Scientific and Investigative Techniques Stuart

Chapter 16Chapter 16 CRC Press: Forensic Science, James and NoCRC Press: Forensic Science, James and Nordby, 2nd Editionrdby, 2nd Edition

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Forensic ScienceForensic ScienceAn Introduction to Scientific and An Introduction to Scientific and

Investigative TechniquesInvestigative Techniques

Stuart H. James and Jon J. NordbyStuart H. James and Jon J. Nordby

22Chapter 16Chapter 16 CRC Press: Forensic Science, James and NoCRC Press: Forensic Science, James and Nordby, 2nd Editionrdby, 2nd Edition

Chapter 16Chapter 16

Microanalysis and Microanalysis and Examination of Trace Examination of Trace

EvidenceEvidenceChapter Authors: Thomas A. Kubic and Chapter Authors: Thomas A. Kubic and

Nicholas PetracoNicholas Petraco

• Presentation created by Greg Galardi, Peru, NebraskaPresentation created by Greg Galardi, Peru, Nebraska


MicroanalysisMicroanalysis

• MicroanalysisMicroanalysis is the application of a is the application of a microscope and microscopical microscope and microscopical techniques to the observation, techniques to the observation, collection, and analysis of collection, and analysis of microevidence that can not be clearly microevidence that can not be clearly observed or analyzed without such observed or analyzed without such devicesdevices

• Deals with samples in milligram or Deals with samples in milligram or microgram size rangesmicrogram size ranges


Trace EvidenceTrace Evidence

• Trace evidence - qualitative or Trace evidence - qualitative or quantitative analysis of the minor or quantitative analysis of the minor or ultraminor components of a sample ultraminor components of a sample

• Sample – entire submitted exhibit or a Sample – entire submitted exhibit or a subsample of the exhibitsubsample of the exhibit


Forensic LaboratoriesForensic Laboratories

• Large forensic laboratories are Large forensic laboratories are generally more specific: fiber, hair, generally more specific: fiber, hair, mineralogy, paint, serology, firearms mineralogy, paint, serology, firearms analyses, controlled substancesanalyses, controlled substances

• Small laboratories may be grouped Small laboratories may be grouped differently, such as in sections of differently, such as in sections of chemistry, biology, microscopy, drugs chemistry, biology, microscopy, drugs and ballisticsand ballistics


Instruments of Microanalysis Instruments of Microanalysis and Sample Typesand Sample Types

• Microscopes are first tool used to Microscopes are first tool used to examine evidenceexamine evidence

• Stereo binocular microscopes, Stereo binocular microscopes, compound in nature, are often usedcompound in nature, are often used

• Lens – optical component that may be Lens – optical component that may be composed of one or several elementscomposed of one or several elements



• Stereo microscopes have two separate Stereo microscopes have two separate eyepieces, and views are separated by eyepieces, and views are separated by a small angle (15 degrees)a small angle (15 degrees)

• Use of stereo microscopes allows for Use of stereo microscopes allows for item being examined to been seen item being examined to been seen separately by each eye. This creates separately by each eye. This creates the appearance of three-dimensions.the appearance of three-dimensions.

• Stereo microscopes are normally used Stereo microscopes are normally used with reflected lightwith reflected light



• Compound binocular microscope – Compound binocular microscope – second most common type of second most common type of microscope encountered in laboratorymicroscope encountered in laboratory

• Two eyepieces are present, however, Two eyepieces are present, however, both eyes see the same imageboth eyes see the same image

• This microscope often employs This microscope often employs transmitted, bright field illuminationtransmitted, bright field illumination


Terminology of a MicroscopeTerminology of a Microscope

• ObjectiveObjective (OBJ) (OBJ)• Eyepiece Eyepiece (EP)(EP)• Magnification (x)Magnification (x) – amount subject is – amount subject is

enlarged by lens system, the objective, enlarged by lens system, the objective, eyepiece or othereyepiece or other

• Working Distance (WD)Working Distance (WD) – distance – distance between the subject and the closest between the subject and the closest portion of the objective when focusedportion of the objective when focused



• Depth of Field (DF)Depth of Field (DF) – total distance, – total distance, height, above and below the point of height, above and below the point of focus that appears clearly focusedfocus that appears clearly focused

• Angle of Acceptance (AA)Angle of Acceptance (AA) – maximum – maximum angle between light waves that an OBJ angle between light waves that an OBJ can collectcan collect

• Numerical Aperture (NA)Numerical Aperture (NA) - NA = N sin - NA = N sin AA/2AA/2



• Resolving Power (RP)Resolving Power (RP) - Ability to - Ability to distinguish fine differences in structuredistinguish fine differences in structure

• N N - lowest refractive index (RI) material - lowest refractive index (RI) material between the subject and the objectivebetween the subject and the objective

• Refractive Index (RI)Refractive Index (RI) – Velocity of a – Velocity of a light in a vacuum divided by the light in a vacuum divided by the velocity of light in the medium of velocity of light in the medium of interestinterest


MicrometryMicrometry

• A scale calibrated with a stage A scale calibrated with a stage micrometer can be placed in the micrometer can be placed in the eyepiece of microscope to measure an eyepiece of microscope to measure an items:items:• LengthLength• WidthWidth• ThicknessThickness


Other Alternative Uses of Other Alternative Uses of MicroscopesMicroscopes

• Chemical tests can be performed on Chemical tests can be performed on micro or ultramicro samples under a micro or ultramicro samples under a microscopemicroscope

• Color and micro-crystal tests for Color and micro-crystal tests for identification of substances, or identification of substances, or reactions to a solvent can be observedreactions to a solvent can be observed


LightLight

• Light is a wave phenomenon. Its Light is a wave phenomenon. Its characteristics include:characteristics include:• VelocityVelocity• WavelengthWavelength• FrequencyFrequency• AmplitudeAmplitude• Vibration directionVibration direction• Wavelength and frequency are inversely Wavelength and frequency are inversely

relatedrelated


LightLight

• Can become partially or totally Can become partially or totally polarized by:polarized by:• ReflectionReflection• AdsorptionAdsorption• Propagation through an anisotropic Propagation through an anisotropic

materialmaterial


LightLight

• Normal light is randomly polarized, Normal light is randomly polarized, which means vibration direction of light which means vibration direction of light is in all directions (360 directions)is in all directions (360 directions)

• Plane polarized light - vibration is only Plane polarized light - vibration is only in one direction in one direction


Polarized Light MicroscopePolarized Light Microscope

• Polarized Light Microscopes (PLMs) Polarized Light Microscopes (PLMs) also may have an accessory slot in the also may have an accessory slot in the intermediate accessory tube, which intermediate accessory tube, which allows for placement of additional allows for placement of additional devices into optical path devices into optical path



• Compound microscope fitted with Compound microscope fitted with certain accessories can be converted certain accessories can be converted to a polarized light microscope (PLM)to a polarized light microscope (PLM)

• Two polarizing elements:Two polarizing elements:• Polarizer- placed in condenser mount prior Polarizer- placed in condenser mount prior

to lensto lens• Analyzer – usually positioned in body of Analyzer – usually positioned in body of

microscope in intermediate accessory microscope in intermediate accessory tubetube



• Most analytical capability is the Most analytical capability is the characteristic RIs of anisotropic characteristic RIs of anisotropic materialsmaterials

• Materials are divided into uniaxial and Materials are divided into uniaxial and biaxial classesbiaxial classes

• RIs of these materials are characteristic RIs of these materials are characteristic rather than universal unless certain rather than universal unless certain parameters of measurement are parameters of measurement are controlled and statedcontrolled and stated



• Instrument of choice to characterize Instrument of choice to characterize many forms of microscopic materialsmany forms of microscopic materials

• Can lead to clear, unambiguous Can lead to clear, unambiguous identifications and can aid significantly identifications and can aid significantly in individualization and associationin individualization and association

• There are other microscopes that are There are other microscopes that are used, comparison microscopes and used, comparison microscopes and macroscopes that are usedmacroscopes that are used



• Most common accessories for Most common accessories for accessory slot of a PLM are accessory slot of a PLM are compensatorscompensators

• Compensator- anisotropic materials of Compensator- anisotropic materials of known birefringence constructed so known birefringence constructed so that thickness is controlled and that thickness is controlled and orientations of vibration are knownorientations of vibration are known

• Compensators can be fixed or variable, Compensators can be fixed or variable, and measure retardation in nanometersand measure retardation in nanometers


MacroscopesMacroscopes

• Lowest total magnifications are found Lowest total magnifications are found on macroscopes: seldom rise above 60 on macroscopes: seldom rise above 60 diametersdiameters

• Use reflected light to examine evidenceUse reflected light to examine evidence• Very useful in identification of large Very useful in identification of large

tool marks, fabrics, and ballistic marks tool marks, fabrics, and ballistic marks (stria) on cartridges(stria) on cartridges


MicrospectrophotometryMicrospectrophotometry

• Instruments that generate Instruments that generate transmission, reflection, or adsorption transmission, reflection, or adsorption spectra from various translucent or spectra from various translucent or opaque samplesopaque samples

• Principal types of instruments are Principal types of instruments are visible and infraredvisible and infrared

• Commonly used to analyze colored Commonly used to analyze colored fibers or paint surfacesfibers or paint surfaces


Scanning Electron Microscope Scanning Electron Microscope (SEM)(SEM)

• a microscope that permits viewing of a microscope that permits viewing of samples at much greater magnification samples at much greater magnification and resolution than is possible by light and resolution than is possible by light microscopesmicroscopes

• Magnification is possible in the range Magnification is possible in the range of 10 to 100,000xof 10 to 100,000x

• When combined with a energy When combined with a energy dispersive x-ray spectrometer, (EDS) dispersive x-ray spectrometer, (EDS) this tool becomes invaluable this tool becomes invaluable


Scanning Electron Microscope Scanning Electron Microscope

• SEM/EDS combination can readily resolve a SEM/EDS combination can readily resolve a particle smaller than 1 micrometer in size, particle smaller than 1 micrometer in size, while generating spectra revealing elemental while generating spectra revealing elemental size of objectsize of object

• SEMs are more valuable due to development SEMs are more valuable due to development of low pressure or low vacuum systems of low pressure or low vacuum systems which allow sample being studied not to be which allow sample being studied not to be kept at such great reductions in pressurekept at such great reductions in pressure


Other Instrumental Techniques Other Instrumental Techniques of Value to a Microanalystof Value to a Microanalyst

• X-Ray diffractionX-Ray diffraction• Pyrolysis Gas Chromatography/Mass Pyrolysis Gas Chromatography/Mass

spectrometry spectrometry • X-ray fluorescenceX-ray fluorescence• Atomic absorptionAtomic absorption• Atomic emissionAtomic emission• Atomic Mass SpectrometryAtomic Mass Spectrometry


Microscopic Evidence and its Microscopic Evidence and its Analysis - GlassAnalysis - Glass

• Glass is a common type of evidenceGlass is a common type of evidence• Commonly encountered as transfer Commonly encountered as transfer

evidenceevidence• Examination of a broken window can Examination of a broken window can

reveal whether the impact that caused reveal whether the impact that caused the fracture was caused by low or high the fracture was caused by low or high velocity blunt traumavelocity blunt trauma



• Radial crack – those cracks originating Radial crack – those cracks originating from impact point and propagating from impact point and propagating awayaway

• Concentric crack- those cracks Concentric crack- those cracks seeming to make a circle around the seeming to make a circle around the point of impactpoint of impact



• Conchoidal lines – those edge Conchoidal lines – those edge characteristics of glass fractures. They characteristics of glass fractures. They are stress marks shaped like arches are stress marks shaped like arches that are perpendicular to one glass that are perpendicular to one glass surface and curved nearly parallel to surface and curved nearly parallel to the opposite surface. The the opposite surface. The perpendicular surface faces the side perpendicular surface faces the side where the crack originatedwhere the crack originated



• When microscopic glass chips are When microscopic glass chips are examined, the following properties are examined, the following properties are evaluated:evaluated:• Physical – thickness, uniformity, Physical – thickness, uniformity,

color, curvature, surface conditions-color, curvature, surface conditions-tinting, soiling, etctinting, soiling, etc

• Optical – most significant property is Optical – most significant property is Refractive IndexRefractive Index

• ElementalElemental – – composition of glasscomposition of glass



• In order to determine whether liquid In order to determine whether liquid medium or solid sample has a higher medium or solid sample has a higher refractive index, three methods are refractive index, three methods are commonly used:commonly used:• Oblique IlluminationOblique Illumination• Dispersion staining colorDispersion staining color• Movement of Becke lineMovement of Becke line

• However, better accuracy is required However, better accuracy is required for advanced criminalistics workfor advanced criminalistics work


Microscopic Evidence and its Microscopic Evidence and its Analysis – Hairs and FursAnalysis – Hairs and Furs

• Hairs and furs are natural fibers of Hairs and furs are natural fibers of animal originanimal origin

• Hair examiners can often conclusively Hair examiners can often conclusively eliminate a person as a source of haireliminate a person as a source of hair

• However, rarely can the examiner However, rarely can the examiner absolutely associate a hair to a personabsolutely associate a hair to a person

• Hairs are generally grouped by racial Hairs are generally grouped by racial origin and body locationorigin and body location


Microscopic Evidence and its Microscopic Evidence and its Analysis – Hairs and FursAnalysis – Hairs and Furs

• Furs can generally be classified by Furs can generally be classified by species with a microscopespecies with a microscope

• Subclassification of fur is difficult Subclassification of fur is difficult without an extensive reference without an extensive reference collectioncollection

• Basic characteristics of color, length Basic characteristics of color, length and curliness may be valuableand curliness may be valuable


Microscopic Evidence and its Microscopic Evidence and its Analysis – Hair and FurAnalysis – Hair and Fur

• Hair and Fur are composed of keratin, Hair and Fur are composed of keratin, melanin and trace metals melanin and trace metals

• Structure of hair :Structure of hair :• Cuticle- outermost portion of hairCuticle- outermost portion of hair• Cortex – contains cortical fusi and Cortex – contains cortical fusi and

ovoid bodies and is between medulla ovoid bodies and is between medulla and cuticleand cuticle

• Medulla- center portionMedulla- center portion



• Parts of hair or fur:Parts of hair or fur:• Proximal end - Root portion or bulb Proximal end - Root portion or bulb • Distal end - Tip of hairDistal end - Tip of hair• Anagen Stage- Period of growth of Anagen Stage- Period of growth of

hairhair• Catagen Stage – Transition phaseCatagen Stage – Transition phase• Telogen Stage – dormant or Telogen Stage – dormant or

sloughing stagesloughing stage



• Racial origin of hair can be determined Racial origin of hair can be determined and classified as Caucasian, Negroid or and classified as Caucasian, Negroid or MongoloidMongoloid

• Scales cover the shaft of the hair and Scales cover the shaft of the hair and point away from proximal end to distal point away from proximal end to distal end. end.

• The scale structures are normally The scale structures are normally divided into three different types.divided into three different types.



• Types of scales are:Types of scales are:• Petal – triangular or protrude from shaft Petal – triangular or protrude from shaft

and usually found on cats, seals, minksand usually found on cats, seals, minks• Imbricate – flattened scales, like shingles Imbricate – flattened scales, like shingles

on a roof and generally found on humanson a roof and generally found on humans• Mosaic -resemble stacks of paper cups Mosaic -resemble stacks of paper cups

and found on small rodents and bats, and found on small rodents and bats, rarely humansrarely humans



• Hair can be determined from any Hair can be determined from any location: head, pubic area, limb, beard location: head, pubic area, limb, beard chest, pubic, axillary or other areas.chest, pubic, axillary or other areas.

• Trace metal comparison in hairs has Trace metal comparison in hairs has met with limited successmet with limited success


Microscopic Evidence and its Microscopic Evidence and its Analysis – FibersAnalysis – Fibers

• Fibers are a common class of Fibers are a common class of microscopic evidence. microscopic evidence.

• They have numerous major They have numerous major classifications and generic subtypes, classifications and generic subtypes, are physically different, are processed are physically different, are processed many ways, transfer easily, have many ways, transfer easily, have significant persistence and thus are significant persistence and thus are valuable forensic evidence.valuable forensic evidence.



• Fibers may be grouped as animal, Fibers may be grouped as animal, vegetable, or mineralvegetable, or mineral

• Also categorized as naturally Also categorized as naturally occurring, manufactured, and syntheticoccurring, manufactured, and synthetic

• Use of microscopy for initial Use of microscopy for initial examination and collection of first examination and collection of first analytical data is accepted forensic analytical data is accepted forensic procedureprocedure



• Fiber is analyzed under Fiber is analyzed under microscope and the following are microscope and the following are documented:documented:• Size, Crimp, Color ,Luster, Possible Size, Crimp, Color ,Luster, Possible

cross section, Damage, Soil and cross section, Damage, Soil and Adhering debrisAdhering debris

• Initial examination is followed by Initial examination is followed by examination with PLMexamination with PLM



• Examination of fibers is carried out Examination of fibers is carried out under crossed polars and with plane under crossed polars and with plane polarized lightpolarized light

• Fiber is determined to be isotropic or Fiber is determined to be isotropic or anisotropicanisotropic

• Almost all isotropic fibers are from Almost all isotropic fibers are from glassglass

• SEM/EDS allow determination of SEM/EDS allow determination of elemental composition of fiberelemental composition of fiber


Microscopic Evidence and its Microscopic Evidence and its Analysis –PaintAnalysis –Paint

• Paint samples are a major portion of Paint samples are a major portion of microsamples submitted to microsamples submitted to laboratorieslaboratories

• Paint samples usually involve paint Paint samples usually involve paint transfer and vehicular accidentstransfer and vehicular accidents

• Paint transfer from architectural Paint transfer from architectural sources- crimes against property are sources- crimes against property are submitted occasionallysubmitted occasionally



• Paint is composed of:Paint is composed of:• BindersBinders which hold all components which hold all components

together and is of a polymeric nature, together and is of a polymeric nature, consisting of natural or synthetic resinsconsisting of natural or synthetic resins

• Pigments Pigments which supply paint colorwhich supply paint color• ExtendersExtenders are added to paint to increase are added to paint to increase

its solid content and its opacity and hiding its solid content and its opacity and hiding ability ability



• Modifiers are added to paint Modifiers are added to paint formulations and affect paint film’s formulations and affect paint film’s durability, gloss, flexibility, hardness, durability, gloss, flexibility, hardness, resistance to ultraviolet radiation, and resistance to ultraviolet radiation, and other characteristicsother characteristics

• Paint films can be investigated Paint films can be investigated according to a number of physical and according to a number of physical and chemical characteristicschemical characteristics



• When paint is to be analyzed, it is best When paint is to be analyzed, it is best to submit entire object to laboratoryto submit entire object to laboratory

• When this is impractical, paint must be When this is impractical, paint must be removed from object and submittedremoved from object and submitted

• Collect sample from area very near area Collect sample from area very near area of alleged contact and any other of alleged contact and any other additional samplesadditional samples



• First part of paint examination is the First part of paint examination is the goal of obtaining a physical matchgoal of obtaining a physical match

• Fit of jigsaw edges or match of surface Fit of jigsaw edges or match of surface striae questioned is strong evidencestriae questioned is strong evidence

• If physical match is not obtained, layer If physical match is not obtained, layer structure order, color, thickness, and structure order, color, thickness, and other details should be documentedother details should be documented



• Angle cuts and thin sectioning with a Angle cuts and thin sectioning with a scalpel also can reveal layer structurescalpel also can reveal layer structure

• Chemical reactions can also serve as Chemical reactions can also serve as sources of datasources of data

• Fluorescence microscopy, Infrared Fluorescence microscopy, Infrared microspectrophotometry and recently microspectrophotometry and recently available Raman microspectrometers available Raman microspectrometers are all other options for analyzing paintare all other options for analyzing paint



• SEM/EDS, x-ray diffraction, x-ray SEM/EDS, x-ray diffraction, x-ray fluorescence, pyrolysis with gas fluorescence, pyrolysis with gas chromatography also may be usedchromatography also may be used


Microscopic Evidence and its Microscopic Evidence and its Analysis- SoilsAnalysis- Soils

• PLMs are excellent tools for soil PLMs are excellent tools for soil analysisanalysis

• Soils are separated, then the minerals Soils are separated, then the minerals are identified by color, shape, and are identified by color, shape, and optical propertiesoptical properties

• Mineral content of soil assists in Mineral content of soil assists in indicators of location of soil sample indicators of location of soil sample


Microscopic Evidence and its Microscopic Evidence and its Analysis – Gunshot ResidueAnalysis – Gunshot Residue

• Gunshot Residue (GSR) is a mixture of Gunshot Residue (GSR) is a mixture of organic and inorganic materials organic and inorganic materials originating from the projectile, originating from the projectile, cartridge case, propellant, and primer cartridge case, propellant, and primer that emerge from the barrel and that emerge from the barrel and openings of the firearmsopenings of the firearms

• Determination of GSR is to confirm Determination of GSR is to confirm residue is indeed GSRresidue is indeed GSR



• Methods to analyze gunshot residue Methods to analyze gunshot residue include Instrumental neutron activation include Instrumental neutron activation analysis, graphite furnace atomic analysis, graphite furnace atomic absorption, and inductively coupled absorption, and inductively coupled atomic emission spectroscopyatomic emission spectroscopy

• Sample is considered when certain Sample is considered when certain elements, normally barium and elements, normally barium and antimony, are found together above a antimony, are found together above a baseline levelbaseline level



• SEM/EDS can be used to analyze SEM/EDS can be used to analyze possible gunshot residuepossible gunshot residue

• Consideration in collection of gunshot Consideration in collection of gunshot residue and analysis should include residue and analysis should include possible environmental contamination, possible environmental contamination, location of sample, and where sample location of sample, and where sample was collected – web of hand, palm, was collected – web of hand, palm, other parts of the body, etcother parts of the body, etc

Documents

Chapter 16 CRC Press: Forensic Science, James and Nordby, 2nd Edition 1# Forensic Science An Introduction to Scientific and Investigative Techniques Stuart