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Trace Evidence > Hair PPT > Flashcards

Hair PPT Flashcards

1
Q

Three types of animal hairs.

A

Vibrissa
Bristle
Wool

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2
Q

Vibrissa hair:

A

Tactile and sensitive whisker of many animals, largest and longest hair on body.

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3
Q

Bristle hair:

A

Coarse bristle or guard hair that provide a protective coat ; can be readily identified, distinctive in appearance and morphology

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4
Q

Wool hair:

A

Fur hair that provides insulation from wet and cold; shorter finer hairs that cover bodies of all mammals.

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5
Q

Types of hair on human body:

A

Primodial
Lanugo
Vellus
Terminal

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6
Q

Primodial

A

Appear at 3rd month of gestation on upper lip, eyebrows, palms and soles of fetus.

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7
Q

Lanugo hair:

A

Found in fetal life, shed after 6th month of gestation. Smooth surface; observed on aborted fetus and can be used in infanticide investigation.

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8
Q

Vellus hair:

A

Spread uniformly over body surface. Soft fine unmedullated, rarely exceed 2cm in length. Cover entire body of human except soles of feet, palms of hands, lips and nipples.

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9
Q

Terminal hair:

A

Coarser hairs that replace vellus at specific sites and times of life; found on scalp, eyebrows, eyelashes, lesser extent on limbs of both sexes at all ages. Puberty accompanied by pubic and axillary hair growth.

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10
Q

Hair is:

A

Appendage of the skin that grows out of an organ called “hair follicle.”

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11
Q

Root is:

A

Portion of hair that lies in the follicle, whereas the portion above skin surface is called the “shaft.”

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12
Q

Bulb is:

A

Enlarged base of the root,which surrounds a mass of loose connective tissue called “dermal papilla.”

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13
Q

Hair is excellent for biological study:

A

The resist biological and chemical degradation.

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14
Q

Hair is excellent for biological study:

A

Hair is composed of a group of proteins called “keratins” that interconnect to form stable fibrils.

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15
Q

Hair is excellent for biological study:

A

Keratin protein chains are complex and produce an integral structure.

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16
Q

Hair is excellent for biological study:

A

Bonding of sulfur atoms between adjacent keratin chains makes them extremely resistant to degradation.

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17
Q

Microscopic structure of hair:

A

Cuticle, medulla and cortex

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18
Q

Cortex is:

A

Inner darker portion of hair

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19
Q

Medulla is:

A

Canal-like structure in the center of the cortex.

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20
Q

Cuticle is:

A

Outer layer of scales that surround the hair shaft.

21
Q

“Color of hair” is due to:

A

pigment granules in the cortex and air bubbles in the medulla.

22
Q

Types of Medulla:

A

Interrupted, Fragmented, Continuous, Absent or not present

23
Q

Hair growth phases:

A

Anagen, Catagen and Telogen.

24
Q

Anagen phase:

80-90 % of follicles

A

Active growth 2 to 6 years.

Follicle actively producing hair. When pulled, follicle tag maybe present, which is good DNA source.

25
Q

Catagen phase:

2% of follicles

A

Transition growth 2 to 3 weeks. Root takes elongated appearance.

26
Q

Telogen phase:

10-18% of follicles

A

Resting phase 5 to 6 weeks. Final growth phase in which hair falls out of the skin. Root takes a club-shaped appearance. After 2 to 6 months of growth, hair will naturally shed.

27
Q

When hair is removed by “Force:”

A

Anagen phase - follicle tissue from root sheath may still be attached.

28
Q

When hair is removed by “Force:”

A

Telogen phase - in resting phase before being shed, could be forcibly removed during an assault, otherwise, no way to tell.

29
Q

When hair is removed by “Force:”

A

Only when tissue is attached can it be said the hair was forcibly removed.

30
Q

Post Mortem:

A

“Decomposition”

  • Color changes
  • Loss of soft tissue
  • Degradation of cortical structure
31
Q

Post Mortem:

A

At decomposition, if anagen hairs are pulled, banding may appear around base of hair.

32
Q

Post Mortem Banding:

A

useful to indicate hair was deposited after death, body has been moved or hairs plucked after death and dropped elsewhere.

33
Q

Identification of human hair:

A

Species origin, racial origin and body or somatic location.

34
Q

Species origin:

A

Scales on “human” cuticular surface are generally small and margins form irregular mosaic. Scales are flattened, outer cuticular margin show little if any serration.

35
Q

Species origin

A

“Animals” exhibit wide range of cuticular patterns.

36
Q

Species origin:

A

“Human” medulla index is less than 1/3 diameter of hair shaft. Untreated hairs are uniform in color. Pigmentation concentrated toward shaft perihery.

37
Q

Species origin:

A

“Animal” medulla greater than 50% of hair shaft. There color changes along the shaft (banding). Pigmentation concentrated around medulla.

38
Q

Racial origin:

A

Three major groups:
Caucasoid
Mongoloid
Negroid

39
Q

Racial origin:

A

Primarily applied to head hair. Racial mixture, limited sample, size, and poorly defined characteristics may make it difficult to conclude racial origin based on hair.

40
Q

Identification of hair:

A 
Look for:
Structure
Color
Cuticular traits
Length
Disease
41
Q

Identification of hair:

A

“Length of Cuticle”

  • length of each hair should be measured directly
  • hair in question must be within range of lengths found in exemplar
  • cuticular surface may reveal comparable damage and scale morphology.
42
Q

Identification of hair:

A

Hair shaft abnormalities do not occur often. Blood crusts, fibers, dandruff. Diseases - unusual banding along hair shaft owing to presence of numerous small irregular air spaces.

43
Q

Identification of hair:

A

Hair can be linked to an individual by DNA in the root or follicular tissue. Pulled hairs have the follicular tag (rich in DNA).

44
Q

Identification of hair:

A

In the absence of follicle tissue, examiner relies on hair root.

45
Q

Identification of hair:

A

“Anagen” phase has higher rate for DNA extraction. Telogen phase has inadequate amount of DNA.

46
Q

Collect hairs for examination:

A

Facial- from mustache,beard and sideburns. Head hair from each of the major regions. Hairs should be pulled from skin. 50 hairs from each region. Vigorous combing or brushing.

47
Q

Instrumentation:

A

Stereomicroscope - determine range of characteristics related to hairs. Aid of different temperature illuminators and colored backgrounds, examiner can discriminate specimens in initial color observations.

48
Q

Instrumentation:

A

Compound microscope

with higher magnification and resolution, delineate hair’s finer characteristics.

49
Q

Instrumentation:

A

Comparison microscope

compare questioned hair samples side by side.

Trace Evidence (17 decks)

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