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FRSC 570 > Microscopic Trace Evidence - Hair > Flashcards

Microscopic Trace Evidence - Hair Flashcards

1
Q

microanalysis is the application of a microscope and microscopically techniques to the

A

observation, collection, and analysis of microevidence that can not be clearly observed or analyzed without such devices

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2
Q

deals with ? in milligram or microgram size ranges

A

deals

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3
Q

what is trace evidence?

A

qualitative or quantitative analysis of the minor or ultraminor components of a sample

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4
Q

what is a sample?

A

entire submitted exhibit or a subsample of the exhibit

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5
Q

first theory of Locard’s Exchange

A

traces of the victim and the scene will be carried away by the perpetrator

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6
Q

second theory of Locard’s Exchange

A

traces of the perpetrator will remain on the victim, and the victim may leave traces of himself or herself on the perpetrator

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7
Q

third theory of Locard’s Exchange

A

traces of the perpetrator will be left at the scene

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8
Q

large forensic laboratories are generally more specific

A

fiber, hair, mineralogy, paint, serology, firearms analyses, controlled substances

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9
Q

small laboraties may be grouped differently, such as in sections of

A

chemistry, biology, microscopy, drugs and ballistics

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10
Q

what is the first tool used to examine trace evidence?

A

first

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11
Q

what type of microscope is compound in nature and often used?

A

stereo binocular microscopes

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12
Q

stereo microscopes have how many eyepieces, and views are separated by a small angle of what?

A

2 separate eyepieces
15 degrees

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13
Q

use of stereo microscopes allows for item being examined to been seen separately by each eye. this creates the appearance of ? dimensions

A

three

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14
Q

stereo microscopes are normally used with ? light

A

reflective

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15
Q

what is a compound binocular microscope

A

second most common type of microscope encountered in laboratory

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16
Q

two eyepieces are present, however, both eyes see the ? image

A

same

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17
Q

this microscope often employs ?, bright field illumination

A

transmitted

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18
Q

a scale calibrated with a stage micrometer can be placed in the eyepiece of microscope to measure an items:

A

length
width
thickness

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19
Q

what to use for the hair lab in order to determine the medullary index of the hairs/furs?

A

micrometer in the compound microscopes

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20
Q

hair is encountered as ? in a wide variety of crimes

A

physical evidence

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21
Q

although it is not yet possible to ? a human hair to any single head or body through its morphology, it still has value as physical evidence

A

individualize

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22
Q

when properly collected and submitted to the laboratory accompanied by an adequate number of standard/reference samples, hair can provide ?

A

strong corroborative evidence for placing an individual at a crime scene

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23
Q

what does a comparison microscope do?

A

an indispensable tool for comparing the morphological charcateristics of hair

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24
Q

when comparing strands of human hair, the criminalist is particularly interested in ?

A

matching the color, length , and diameter

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25
a careful microscopic examination of hair will reveal ?
morphological features that can distinguish human hair from the hair of animals
26
what is particularly important in animal hair identification?
scale structure, medullary index, medullary shape
27
what are the important features for comparing human hair?
the presence or absence of a medulla the distribution, shape, and color intensit of the pigment granules present in the cortex
28
the most common request is to determine whether or not hair recovered at the crime scene ?
compares to hair removed from the suspect
29
however, microscopic hair examinatins tend to be ?
subjective and highly dependent on the skills and integrity of the analyst
30
appendage of skin that grows from the ?
hair follicle
31
hair extends from its ? embedded into the shaft, and temrinates at the tip end
root/bulb
32
it is the shaft, which is composed of three layers: that is subjected to the most intense examination by the forensic scientist
-the cuticle -cortex -medulla
33
hairs and furs are ?
fibers of animal origin
34
hair exmainers can often conclusively ? a person as a source of hair
eliminate
35
however, rarely can the exmainer absolutely ? a hair to a person
associate
36
hairs are generally grouped by ?
racial origin and body location
37
what is an anagen?
active growth phase of hair follicles
38
characteristics of anagen hair phase
-cells in the root of the hair are dividning rapidly, adding to the hair shaft -during this phase, the hair grows about 1 cm every 28 days -scalp hair stays in the active phase of growth for 2-7 years -the amount of time the hair follicle stays in the anagen phase is genetically determined -at the end of the anagen phase an unkown signal causes the follicle to go into the catagen phase -flame-shaped root bulb
39
what are the 3 types of hair phases?
- anagen - catagen - telogen
40
what is the catagen phase?
short transition stage that occurs at the end of the anagen phase. it signals the end of the active growth of a hair. this phase lasts for about 2-3 weeks
41
what type of root bulb does a catagen hair phase have?
elongated root bulb
42
what is the telogen hair phase?
the resting phase of the hair follicle. when the body is subjected to extreme stress, as much as 70 percent of your hair prematurely can enter a phase of rest
43
charcateristics of telogen hair phase
-these hairs begin to fall out -club-shaped root bulb -the club hair is the final product of a hair follicle in the teolgen stage, and is dead hair -fifty to one-hundred club hairs are shed daily from a normal scalp
44
how does the hair growth cycle times vary from scalp?
-the time these phases last varies from person to person -different hair color, and follicle shape affects the timings of these phases
45
cycle time for anagen, catagen, and telogen phase
anagen phase: 2-3 years (occasionally much longer) catagen phase: 2-3 weeks telogen phase: around 3 months
46
eyebrows cycle times for phases
anagen phase: 4-7 months catagen phase: 3-4 weeks telogen phase: about 9 months
47
the cuticle is the ? structure covering the exterior pof the hair (translucent)
scale
48
the scales always point ? the tip of the hair
towards
49
provides resistance to chemical decompisition and retains ? features
structural
50
the scale pattern is useful in ? identifcation
species
51
what is the method of studying the scale pattern of hair?
to make a cast of its surface
52
how is the cast made?
- the hair is embedded into a soft medium like clear nail polish or liquid latex -when the medium has hardened, the hair is removed, leabing a clear, distinct impression of the hair's cuticle -the cuticle can then be viewed under a microscope
53
3 types of scales
spinous imbricate coronal
54
what is a spinous sclae?
triangular or protrude from shaft and usually found on cats, seals, minks, not humans
55
what is an imbricate scale?
flattened scales, like shingles on a roof and generally found on humans
56
what is a coronal scale?
resemble stacks of paper cups and found on small rodents and bats, rarely humans
57
what is the cortex?
the main body of the hair shaft
58
its major forensic importance is the fact that is is embedded with the ? granules that impart hair with color
pigment
59
the color, shape, and distribution of these granules provide the criminalist with important points of ?
comparison among the hairs of different individuals
60
medulla
a cellular column running through the center of the hair
61
the medullary index measures the diameter of the medulla relative ?
to the diameter of the hair shaft
62
for humans, the medulla generally occupies less than ? the diameter of the shaft, while for animals it is generally ? or greater
one-third, one-half
63
the medulla may be continuous, interrupted, ?, ?
fragmented, absent
64
the presence of the medulla varies from individual to individual and ?
even among hairs of a given individual
65
medullae also have differrent shapes, depending on
species
66
types of medulla patterns
fragmented interrupted continuous absent
67
fragmented
starts, stops, starts, stops, small chunks
68
interrupted
startssssss, stops, larger chunks
69
continuous
medulla runs whole entire length of hair shaft
70
absent
no medulla present at all
71
the root and other surroundings cells in the hair follicle provide the ? necessary to produce hair and continue its growth
tools
72
when pulled from the head, some translucent tissue surrounding the hair's shaft near the root may be found. this is called ? tag
follicular
73
by using DNA analysis on the follicular tag, the hair may be ?
individualized
74
what can hair tell us?
-hair can be dtermined from any location: head, pubic area, limb, beard chest, pubic, axillary or other areas -racial origin of hair can determined and classified as Cauccasian, Negroid or Mongoloid -the age of an individual cannot be learned from a hair examination except with infant hair. Nuclear DNA will allow for sex determination
75
was the hair forcibly removed?
-if tissue is present, the hair may have been forcibly removed or removed via brushing/combing -however, forcibly removed hairs may also be void of tissue -may exhibit stretching
76
what can hair tell us with someone being harmed?
-cut -razor -burned
77
what can hair tell us about individualization?
-if a hair has a root attached, it can be identified as belonging to a single person through (nuclear) DNA -if a hair does not have a root, it cannot be individualized. but can be linked maternally (mtDNA)
78
what type of hair is generally collected for forensic hair comparisons?
head hair or pubic hair
79
the collection of ? full length hairs from all areas of the scalp will normally ensure a representative sampling of head hair
50
80
a minimum collection of two ? fulllength pubic hairs should cover the range of characteristics present in pubic hair
two dozen
81
hair samples are also collected from the victims of ?
suspicious deaths during an autopsy
82

FRSC 570 (3 decks)

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