Hair and Fibers

Question 1

fiber definition

Answer 1

the smallest unit of a textile material that has a length many times greater than its diameter

Question 2

how do fibers occur?

Answer 2

• naturally as plant and animal fibers
• synthetic, man-made

Question 3

hairs and fibers - evidence types

Answer 3

• biological &/or physical
• indirect
• trace evidence
• class

Question 4

4 categories of fibers

Answer 4

• animal fiber
• vegetable fiber
• mineral fiber
• man made fiber

Question 5

animal fiber

Answer 5

wool is most common, but only 1% of textile fibers

Question 6

vegetable fiber

Answer 6

• 24% of all textile fibers
• cotton is most common

Question 7

mineral fiber

Answer 7

• rare
• only asbestos

Question 8

man made (synthetic) fibers

Answer 8

75% of all textile fibers

Question 9

characteristics of synthetic/man made fibers

Answer 9

• uniform
• variety of shapes
• absence of features

Question 10

characteristics of animal & vegetable fibers

Answer 10

• irregular only
• circular to oblong
• visible features (cuticle & medulla)

Question 11

what do fiber analysts compare?

Answer 11

• shape
• dye content
• size
• chemical composition
• microscopic appearences

Question 12

fiber association

Answer 12

• fibers from two separate places can be associated via comparison, that does not mean they derive from the same source
• there is no fiber database that provides a probability of origin

Question 13

Fiber Population Studies

Answer 13

relative frequencies of fiber type/color (generic) on particular surfaces

Question 14

Color Block Studies

Answer 14

ability of a specific protocol to discriminate between similar fibers (type/color)

Question 15

Target Fiber Studies

Answer 15

probability of finding significant numbers of a specific fiber type by random chance

Question 16

direct transfer of fibers

Answer 16

fibers may be transferred from a victim to a suspect

Question 17

example of direct transfer of fibers

Answer 17

fibers from victims sweater found on suspect

Question 18

secondary transfer of fibers

Answer 18

fibers are picked up by victim and then transferred to suspect

Question 19

example of secondary transfer of fibers

Answer 19

victim picks up fibers from his/her couch earlier in day & then transfers to the suspect later

Question 20

how is primary vs secondary transfer determined?

Answer 20

can be determined if the order of events is known

Question 21

what kind of timing is essential for fiber collection?

Answer 21

early collection

Question 22

why is it essential that fibers are collected early?

Answer 22

within 24 hours an estimated 95% of all fibers may have fallen off a victim or been lost from a crime scene

Question 23

which fibers at the crime scene are investigated?

Answer 23

only fibers not expected to be found at a crime scene are investigated

Question 24

textile shedding

Answer 24

the most common form of fiber transfer to be encountered is the shedding from a textile

Question 25

textile (fabric)

Answer 25

a flexible, flat material made by interlacing yarns

Question 26

examples of textiles

Answer 26

- clothing - carpets - upholstery

Question 27

which is the smallest: fiber, yarn, textile

Answer 27

fiber

Question 28

which is the biggest: fiber, yarn, textile

Answer 28

textile

Question 29

5 major types of weave patterns

Answer 29

- plain - basket - satin - twill - leno

Question 30

what determines the weave pattern?

Answer 30

warp and weft

Question 31

warp

Answer 31

length wise fiber

Question 32

weft

Answer 32

crosswise fiber

Question 33

plain weave pattern

Answer 33

- alternating warp & weft pattern - single fibers

Question 34

basket weave pattern

Answer 34

- alternating warp & weft pattern - double fibers

Question 35

satin weave pattern

Answer 35

weft goes over 3 or more warps

Question 36

leno weave pattern

Answer 36

adjacent weft threads cross over each other

Question 37

twill weave pattern

Answer 37

- weft goes over two then under two warps - warp goes over two then under two wefts

Question 38

thread count

Answer 38

threads per inch

Question 39

high thread count =

Answer 39

higher price

Question 40

what kind of fiber analyzing techniques are prioritized?

Answer 40

non-destructive techniques

Question 41

dyes can be analyzed with Thin Layer Chromatography (TLC)

Answer 41

dye components are separated by their differential migration caused by a mobile phase flowing through a porous, absorptive medium

Question 42

what are the variations of hair?

Answer 42

- color - length - diameter - body distribution

Question 43

how are hair variations influenced?

Answer 43

influenced by ancestral affinity and age

Question 44

3 main parts of hair

Answer 44

- cuticle - cortex - medulla

Question 45

cuticle

Answer 45

outside transparent covering

Question 46

cortex

Answer 46

- 2nd layer made of keratin & embedded with melanin - contains air sacs called cortical fusi - gives hair color, form, and shape

Question 47

medulla

Answer 47

- innermost layer running down the center of the cortex - gives hair its flexibility & offers insulation

Question 48

advantages to hair toxicology

Answer 48

- easy to collect and store - externally available - can provide info on the individuals history of drug use or evidence of poisoning

Question 49

animal cuticle types

Answer 49

- coronal - spinous

Question 50

human cuticle type

Answer 50

imbricate

Question 51

medulla types

Answer 51

- fragmentary - interrupted - continuous - stacked - absent

Question 52

human medulla types

Answer 52

- fragmentary - interrupted - continuous

Question 53

animal medulla types

Answer 53

- continuous - stacked

Question 54

medullary index

Answer 54

width of medulla / width of cortex

Question 55

typical human medullary index

Answer 55

0.33 or less

Question 56

typical animal medullary index

Answer 56

0.50 or more

Question 57

collecting hairs

Answer 57

collect 30-50 hairs from each body region

Question 58

Postmortem Root Band (PMRB)

Answer 58

proteomic analysis of decedent scalp hair segments exhibiting a postmortem hair root band