1. Hair, Fibers and Paint Chapter 8
Hair Characteristics
Fiber Characteristics
Regenerated Fibers
Paint Chips- color & layer
Automobile finishes
FSHairFiberPaint2007

2. Hair Analysis in Forensic Investigations
hair can provide strong corroborative evidence due to the known characteristics of hair and the resistance of hair to chemical breakdown over time.
one problem: it is impossible to individualize a human hair to a specific head or body.

3. Hair is Class Evidence
•Can often determine body area of origin and sex
•Can often determine racial origin
Negroid kinky with dense uneven pigment flat to oval in shape Caucasian straight or wavy fairly evenly distributed pigment oval to round shape
Mongoloid:
thick, densely pigmented, presence of continuous medulla

4. Hair
Human Hair:
All mammals have hair: a slender, threadlike outgrowth of the epidermis.
Each strand of hair is composed of a scleroprotein called keratin and lacks both blood vessels and nerves.
Both the color and form of human hair and the shape of the hair follicle serve as reliable determinants of racial and ethnic heredity.

5. Physiology of hair:
hair follicle: organ beneath the skin; living cells;
good source of DNA, if attached

6. Structure of a hair follicle:

7. Morphology of Hair
Cuticle- contain scales on exterior of hair shaft (keratinized)
Cortex- main body of shaft, contains pigment granules, characteristic shape
Medulla- is either absent or 1/3 the diameter of the shaft; other animals it is ½ or greater; continuous, interrupted, segmented or absent
Cuticle and Medulla are best used to distinguish if the sample is human or animal

8. hair shaft: composed of three layers cuticle: overlapping scales on outside of hair shaft; point toward the distal end (tip) of hair; specific to species
cuticle
medulla
cortex
human dog deer
Human cuticle is imbricate (looks like cracked
glass); cat is coronal (like a crown); rabbit is spinous
rabbit cat horse

9. pattern allows for species identification a cast can be made of scales in clear nail polish or soft vinyl and viewed under a comparison microscope
cuticle continued:
pattern allows for species identification
a cast can be made of scales in clear nail polish or soft vinyl and viewed under a comparison microscope

10. cortex: layer under the cuticle; 90 % of human hair; pigmented area; colored granules embedded in cells that run parallel to shaft; criminalists compare color, shape and distribution of pigment granules
cuticle
cortex
pigment
granules

11. medulla: center of hair shaft; in humans, if present, ~ half the diameter of the hair. medullary index: measure of the diameter of the medulla relative to the diameter of the hair; expressed as a fraction; humans > 1/3; animals have a medullary index of > 1/2.
medulla

12. Medullary classifications:
continuous:
interrupted:
fragmented:
absent

13. Examples of medulla in human head hair of same person:
continuous
absent
fragmented

14. medulla characteristics differ from person to person and from hair to hair of same person!! some hairs have no medulla at all! human head hairs usually do not have a medulla; if present, it is rarely continuous; usually fragmented Mongoloid hair (Asian race) almost always has a medulla and is continuous… see the dilemma??

15. Medulla shape: differ by species
human: cylindrical
cat: string of pearls
dog: bubbles
deer: honey comb
rabbit: large, fragmented

16. Medulla characteristics for selected mammals:
human head dog deer
rabbit cat mouse

17. The growth of human hair
the root of human hair is contained in the follicle
the root can provide information about the growth
phase of the hair
Developmental stages of growth:
anagenic: lasts up to six years; the root is attached to the
follicle for continued growth; the root has a flame
shape at the end called the folliclular tag, that can
be used for DNA testing, due to presence of actively
dividing, living cells

18. catagenic: time of slow growth; lasts up to three weeks;
hair has elongated root tip

19. telogenic: growth is over; called the resting phase;
root tip has a club shape; the hair is pushed
out of the follicle over a two to six month
period (natural shedding)

20. Hair Growth Hair growth is comprised of three different phases which are as follows:
The ANAGENIC Phase (Growth) Hair is produced by dermal papilla cells.
The CATAGENIC Phase (Shedding) In this second phase, the papilla ceases secreting and hair falls out.
The TELOGENIC Phase (Rest) The papilla reaches a dormant state.

21. Questions that can be answered by hair analysis:
Area of body the hair originated from
Head, arm, chest, pubic
Racial origin……usually
Presence of and characteristics of medulla
Pigment presentation and distribution
Typical characteristics: curl, kink, straightness, etc.
Age and gender…sometimes
Only infant hair can be aged for sure
Dyes and other chemical treatments may give some clues
If follicular cells are present: DNA analysis
Individualize
Nuclear tag: DNA and mitochondrial DNA analysis

22. Questions that can be answered by hair analysis:
Poisoning and/or drug use
hair grows at a regular rate (about ½ inch per month);
residuals of chemicals ingested become part of hair’s
structure and can be analyzed
Trauma…
presence of follicular tag means hair was pulled out and
not shed naturally
Cross transfer
place suspect at crime scene
connect a suspect to a weapon
determine route to or from crime scene

23. Hair as evidence Where to look for hair evidence: the victim the crime scene the weapon a tool a vehicle an article of clothing the suspect

24. Collection of Hair Evidence
It is recommended that hair samples be collected from
various areas of the victim’s body in all homicide cases:
even if there in no initial hair evidence; samples should be collected before burial or cremation
samples should be collected by pulling or plucking to ensure obtaining a follicular tag or piece of the root for DNA and mDNA
reference samples or standards must be from the same area of the body as the suspect sample, as hair from different body areas exhibit different characteristics

25. Collection of Hair Evidence, continued
A sampling of hairs is recommended Hair removed from the head should be taken from the front, back, left, right and top Samples with roots should be air dried Use oblique lighting, scan the surfaces Use tweezers, being careful not to bend or break the hair Hairs can be gathered by tape lifting also Place samples in sterile container and seal; folded paper or envelops may be used as well; label to start COC; include in field notes

26. Hair is class evidence; it is usually NOT possible to determine in
court that a particular hair sample specifically came from a
certain person
Careful observations and analysis of hair samples can lead to other
evidence and corroborate it
Criminologists are interested in the microscopic examination of
hair samples by analyzing
color: distribution and intensity of pigment granules
length
diameter
medulla characteristics and medullary index
cuticle structure and integrity
presence of cortical fusi (air spaces in cortex, near the
proximal end)

27. Hair samples are prepared as whole mounts and as casts of scale patterns

28. Whole mount slides of hair samples

29. Scale casts of hair samples

30. Hair, Fibers and Paint Chapter 8
Fiber characteristics
Fiber as evidence

31. Fiber: any piece of natural or synthetic material
used for clothing, home furnishings and other
products.

32. Fibers can be classified into two broad categories
- natural and man-made
Natural fibers are derived from animal, vegetable
or mineral sources. 
Animal fibers include furs, wool, silk, horsehair, and
animal hairbrushes
  Vegetable fibers include cotton, linen, jute, hemp,
and sisal. Many ropes, clothes, paper, and packing
materials are made from vegetable fibers. 
Mineral fibers include asbestos, glass wool, and
fiberglass. Products such as insulation, auto body
repairs, clothing, drapery, safe insulation, and fire
proofing are produced from mineral fibers. 

33. By far, the most commonly encountered natural fiber is cotton
          By far, the most commonly encountered natural fiber is cotton.  However, due to the commonality of white and blue denim fibers produced from cotton, cotton fibers of these colors have little evidentiary value.

34. Man made fibers:
more than half of all fibers used in the production of
textile materials are man-made.
some originate from natural materials such as cotton
or wood
others originate from synthetic materials.
polyesters and nylons are the most common man-made
fibers, followed by acetate, acrylics and rayon

35. Regenerated fibers are a type of man made fiber manufactured from natural raw materials in which pure cellulose is extracted and chemically treated.  This type of fiber includes rayon, acetate, and triacetate fibers.  
Synthetic fibers are produced solely from synthetic polymers, long chains of molecules. These include nylon, polyester, and acrylic fibers.   These fibers can be found in clothes, drapery, bindings, fishing lines, and hosiery.

36. Cross transfers of fiber often occur in cases in which there is person-to-person contact, and investigators hope that fiber traceable back to the offender can be found at the crime scene, as well as vice versa.  Success in solving the crime often hinges on the ability to narrow the sources for the type of fiber found.
The problem with fiber evidence is that fibers are not unique.  Unlike fingerprints or DNA, they cannot pinpoint an offender in any definitive manner.  There must be other factors involved, such as evidence that the fibers can corroborate or something unique to the fibers that set them apart. For example, when fibers appeared to link two Ohio murders in the 1980s, it was just the start of building a case, but without the fibers, there would have been no link in the first place.

37. As is the case with glass and paint, a positive association in forensic fiber analyses is usually not a conclusive identification. 
A positive association will typically result in a conclusion that a questioned fiber is consistent with a known fabric. 
The importance of this finding may be directly related to how rare or how common the specimens may be, in terms of availability. 
Again, no statistical data is typically applied to this type of conclusion.  

38. The first step in fiber analysis is to compare color and diameter
The first step in fiber analysis is to compare color and diameter.  If there is agreement, then the analysis can go into another phase. 
Dyes can also be further analyzed with chromatography, which uses solvents to separate the dye's chemical constituents. 
Under a microscope, the analyst looks for lengthwise striations or pits on a fiber's surface, or unusual shapes—such as with the one short and two long arms of the tri-lobal fibers.
lengthwise
cross sectional of nylon

39. Generally, the analyst gets only a limited number of fibers to work with—sometimes only one.  Whatever has been gathered from the crime scene is then compared against fibers from a suspect source, such as a car or home, and the fibers are laid side by side for visual inspection through a microscope.
A compound microscope uses light reflected from the surface of a fiber and magnified through a series of lenses, while the comparison microscope (two compound microscopes joined by an optical bridge or a stereomicroscope) is used for more precise identification. 
A different device, the phase-contrast microscope, reveals some of the structure of a fiber, while the various electron microscopes either pass beams of electrons through samples to provide a highly magnified image, or reflect electrons off the sample's surface.  A scanning electron microscope converts the emitted electrons into a photographic image for display.  This affords high resolution and depth of focus.

40. Laboratory examination of fibers is principally performed using a polarizing light microscope. Using this instrument and oils of known refractive indices, a scientist can examine and compare color, thickness, cross- sectional shape, amount of delusterant, birefringence, weave pattern, and composition.
Other instrumental techniques, such as FTIR*, are commonly used to determine synthetic fiber composition. UV-VIS microspectrophotometry can be used to discriminate color in the ultraviolet and visible regions that cannot be discerned visibly.
*Fourier Transform  Infra Red
Analysis of dyes present in fibers can also be performed.

41. Fiber microscopy
wool flax cotton

42. Other types of fiber examinations commonly conducted are physical matches of torn fabric and the examination of fabric impressions formed when a fabric contacts a hard surface. 
An example of this type of impression is a corduroy impression from the victim’s pants left in the paint of a suspect vehicle in a hit and run incident. 
The analytical scheme for fiber analysis and comparison varies depending on fiber type and sample size.   This scheme may include polarized light microscopy, micro-FTIR, visible microscpectrophotometry and/or pyrolysis gas chromatography-mass spectrometry.

43. Another useful instrument is the spectrometer, which separates light into component wavelengths.  In 1859, two German scientists discovered that the spectrum of every organic element has a uniqueness to its constituent parts. 
By passing light through something to produce a spectrum, the analyst can read the resulting lines, called "absorption lines."  That is, the specific wavelengths that are selectively absorbed into the substance are characteristic of its component molecules. 
Then a spectrophotometer measures the light intensities, which yields a way to identify different types of substances.

44. A combination of these instruments for the most effective forensic analysis is the micro-spectrophotometer. 
The microscope locates minute traces or shows how light interacts with the material under analysis.  Linking this to a computerized spectrophotometer increases the accuracy. 
The scientist can get both a magnified visual and an infrared pattern at the same time, which increases the number of identifying characteristics of any given material.
microscopic cross section of man-made fiber

45. In short, the fiber analyst compares shape, dye content, size, chemical composition, behavior in and around a flame, analysis of residuals after contact with an open flame and chemical reagents as well as microscopic appearances. Yet all of this is still about "class evidence." 
Even if fibers from two separate places can be matched via comparison, that does not mean they derive from the same source, and there is no fiber database that provides a probability of origin.
analyzing

46. Fibers are gathered at a crime scene with tweezers, tape, or a vacuum
Fibers are gathered at a crime scene with tweezers, tape, or a vacuum.  They generally come from clothing, drapery, wigs, carpeting, furniture, and blankets. 
Fiber transfers can be either direct (primary) or indirect (secondary)
direct (primary): occurs when a fiber is transferred from a
fabric directly onto a victim’s clothing
indirect (secondary): occurs when already transferred fibers
on the clothing of a suspect are transferred to a victim’s
clothing or body
Transfer does NOT always occur and depends upon the type of fiber
or fabric, the duration of contact and the conditions of the garment,
ie damage

47. Other considerations about transfer of fibers: :
length of time between crime and collection of evidence
mobility of victim and suspect
type of physical contact between victim and suspect
how fabric is constructed
tightly vs loosely woven
knitted vs woven
filament vs spun yarns
integrity of the fabric
age
damage
surface fibers

48. Fiber evidence collection:
photograph everything first
remove large objects and carpeting (wear booties!)
place all items separately, in large paper bags; label
start a chain of custody log
have one person collect victim evidence and
another collect suspect evidence
floor surfaces should be vacuumed
smaller surfaces can be taped or scraped and picked

49. Collection of fiber at the crime scene: some considerations
gather elimination fibers from all possible sources,
including personnel
prioritize collection:
collect large items first
proceed to trace evidence
collect other types of evidence next: blood, fingerprints,
bullets, etc.
any damp or blood soaked items must be air-dried

50. Fiber evidence collection methods
scraping vacuuming
and
picking

51. Pertinent information related to the collection of specific
types of fiber evidence:
Socks: of victim; many victims are transported by vehicle;
socks come in contact with the interior of the
vehicle and fibers may be transferred.
Shoes: of both victim and suspect; fibers from rugs and
vehicles can be picked up and deposited by
shoe soles and laces or velcro.
Weapons and other tools: fibers can be picked up in
structural mechanisms of weapons and tools.
Windows and door jams: especially if there is
evidence of a break in.
Bedding items and throw rugs: usually maintain fibers
that are deposited.

52. Characteristics of Fibers
“poly” means
many
“mer” means
unit
Characteristics
Color, diameter, birefringence, shape, presence or absence of delustering particles (usually titanium dioxide)
Rayon
is classified as regenerated fiber (derived from natural material-cellulose)
First man-made fiber 1911
Forensic Fiber
Examination
Guidelines

53. Paint Chapter 8
Paint Chips- color & layer
Automobile finishes

54. Paint Chips Paint Chips
Paint chips- individualized to a single source by examining color and layer structure
Pyrolysis gas chromatography- compares the polymeric make-up of paint binders
Automobile finishes- contain an electro-coat, primers, color coat and clear coat

55. Paint as Trace Evidence
As with most types of "trace evidence" it is not generally possible to individualize paint evidence to a single source to the exclusion of all other sources. Paint exhibits class characteristics.  
The utilization of a proper analytical scheme; however, can make it possible to associate known and questioned samples to the exclusion of most other paint samples in our environment. Then this paint will exhibit individual characteristics.

56. Constituents of Paint Paint consists of three parts:
the "vehicle" or binder which is composed of an organic polymer and additives
the solvent and
pigment which includes inorganic (non-color producing) extender pigments, organic coloring pigments and inorganic coloring pigments. 

57. Paint as a chemical mixture
Paint is really a mixture of components
dissolved or dispersed in a solvent
Components:
pigment:
opacity
color: inorganic and organic compounds
binder:
polymeric substance
support medium for pigment
solvent: dissolves the other components
high vapor pressure: evaporates readily

58. Paint analysis
Through the analysis and classification of paint binder (polymer and additives) systems, the intended end use of the paint (automotive, architectural, industrial) can generally be determined. 
In cases involving automotive paint, the year, make and model of the vehicle from which the paint originated can usually be determined. There’s a data base.  
State of the art analytical schemes for paint analysis include micro-fourier transform infrared spectrometry and pyrolysis gas-chromatography mass-spectrometry for organic components of paint and polarized light microscopy, visible microspectrophotometry and scanning electron microscopy-energy dispersive spectroscopy for inorganic and color analysis.

59. Collecting Paint as Evidence
Paint chips: collect using forceps; careful not to
break the chip
Paint smear: take the whole specimen
Reference samples:
should be uncontaminated
be sure to include all layers
use a scalpel
¼ inch square if possible
Tools and impressions: whole sample

60. Paint chip analysis
The techniques used for glass analysis are also employed for paint chips.  Chips from cars can be compared to samples in the National Automotive Paint File, which holds more than 400,000 samples.  Undercoats help to narrow down the possible manufacturers.  Also the shape of a chip can be matched to an area where a chip is missing, and its chemical constituents can be analyzed via releasing the gases and using gas chromatography.  That creates identifying characteristics for each layer and establishes points of comparison. 

61. Paint analysis
layer structure gas chromatograph

62. Goals of Analysis
To establish common origin and individual characteristics
Tools:
microscope:
color match
layer structure: number and sequence
piecing of chips
gas chromatograph:
determination of chemical make up
infra red spectrophotometer:
binders in paint absorb infra red radiation and
produce a unique spectrum

63. Goals of Analysis continued
Emission spectroscopy:
of paint pigments: can detect elements
present in sample

64. Case Study:
A trace of yellow paint was found in a spot where a rapist had hidden his car was traced to a specific model.  When a suspect was located through a computer database that included those cars, his vehicle showed the scrape at the appropriate height.  With the police on his trail and evidence accumulating, he confessed and was sent to prison.

65. Describe the proper collection and preservation of paint evidence from an automobile suspected of being involved in hit-and-run incident. Paint that is foreign to the suspect automobile is observed on the hood.
Scrape the foreign paint as well as all underlying layers of paint off the car’s surface using a clean knife or scalpel. The scraping must clearly show the layer structure of the paint.
Obtain a control paint sample from an adjacent undamaged area of the car. Again, all layers must be included.
Package each paint specimen separately in a proper container. A druggist fold or a vial makes an excellent container.
Label all specimen containers. Evidence collector’s name or initials, the date, and the sampling location are to be shown. All items collected are to be described in the evidence collector’s field notes.

66. The End