Exam II
Chapters 16, 7, 13, 10 and 12,
Labs 5, 6, 7/8
Chapter 16 Fingerprints
1. What contributions did Henry Faulds, Francis
Galton, Juan Vucetich and Edward Richard Henry
each make to fingerprinting?
• Henry Faulds- claimed that fingerprints did not change over
time and that they could be classified for identification
• Francis Galton- developed a primary classification scheme
based on loops, arches and whorls
• Juan Vucetich- developed a fingerprint classification based on
Galton’s that is used in Spanish-speaking countries
• Edward Richard Henry- in collaboration with Galton instituted
a numerical classification system
2. Why are fingerprints considered individual
evidence and what is the foundation for their
acceptance in court?
• A fingerprint is an individual characteristic because no
two have yet been found to possess identical ridge
characteristics.
• The foundation for their acceptance in court:
- The probability that two fingerprints could match is
low.
- There are an estimated 64 billion different individual
prints.
- This is supported by the millions of individuals who
have had prints taken over the past 90 years in the FBI
central system-- no two have ever been found to be
identical!
3. What are fingerprints?
• Fingerprints are a
reproduction of friction
skin ridges found on the
palm of the fingers and
thumbs.
• Dermal papillae extend
outward and determine
the form and pattern of
ridges on the surface.
• Dermal papillae develop
in the fetus and the ridge
patterns remain
unchanged throughout
life except to enlarge
during growth.
Figure 16-3 Cross section of human skin.
4. How does thin skin differ from thick, or
friction, skin? How does epidermis differ from
dermis?
• Skin is composed of
layers of cells:
- thin skin has 4 layers
- thick/friction skin has
5 layers
• Epidermis is superficial
(outside) to the dermis,
which is deep (inside).
Figure 16-3 Cross section of human skin.
5. Be able to identify ridge characteristics, or
minutiae, on a sample fingerprint.
6. Be able to identify the general ridge
patterns that allow fingerprints to be
systematically classified:
 A loop must have one or more
ridges entering and exiting from
the same side. Loops must have
one delta.
 Types
 radial loop- opens toward
the thumb
 ulnar loop- opens toward
the “pinky” (little finger)
Figure 16-5 Loop pattern.
 A plain whorl or central pocket whorl has at least one ridge
that makes a complete circuit. A double loop is made of two
loops. An accidental is a pattern not covered by other
categories. Whorls have at least two deltas and a core.
Figure 16-6 Whorl patterns.
8
• An arch has friction ridges that enter on one side of the
finger and cross to the other side while rising upward in the
middle. They do NOT have type lines, deltas, or cores.
Figure 16-7 Arch patterns.
7. Be able to calculate an individual’s primary
classification number when given the point
values and equation.
Assign the number of
points for each finger
that has a whorl and
substitute into the
equation:
right
right
index
right
ring
left
left
thumb
left
left
middle little + 1
=
right
right
thumb middle
right
little
left
left
index ring
+1
10
8. What are latent prints?
• Latent fingerprints are those that are not visible to
the naked eye. These prints consist of the natural
secretions of human skin and require development
for them to become visible.
9. What three glands provide the secretions for
latent prints and how do they differ?
• Eccrine- largely water with both inorganic (ammonia,
chlorides, metal ions, phosphates) and organic
compounds (amino acids, lactic acids, urea, sugars).
Most important for fingerprints.
• Apocrine- secrete pheromones and other organic
materials.
• Sebaceous- secrete fatty or greasy substances.
10. Know some techniques for developing latent
prints including powders, iodine, ninhydrin,
silver nitrate, and cyanoacrylate.
• Powders- adhere to both water and fatty deposits.
• Iodine- fumes react with oils and fats to produce a
temporary yellow brown reaction; can be fixed for at
least several weeks with a 1% solution of starch in water
• Ninhydrin- reacts with amino acids to produce a purple color.
• Silver nitrate- reacts with chloride to form silver chloride, a
material which turns gray when exposed to light
• Cyanoacrylate- “super glue” fumes react with water and
other fingerprint constituents to form a hard, whitish deposit.
11. What is sublimation?
• sublimation- solid that turns into a vapor without
passing through a liquid phase
e.g. iodine crystals
12. What other types of prints can be analyzed?
•
•
•
•
Ears- shape, length and width
Voice- electronic pulses measured on a spectrograph
Foot- size of foot and toes; friction ridges on the foot
Shoes- can be compared and identified by type of shoe,
brand, size, year of purchase, and wear pattern
• Lips- display several common patterns like short vertical
or horizontal lines, crosshatching and branching grooves
• Teeth- bite marks are unique and can be used to identify
suspects.
• Eye- the blood vessel patterns in the eye may be unique
to individuals
13. What is AFIS? How was it improved by
IAFIS?
• Automated Fingerprint Identification System
(AFIS)- a computer system for storing and
retrieving fingerprints that began in the 1970’s
 By the 1990’s most large jurisdictions had their
own systems in place. The problem: a person’s
fingerprints may be in one AFIS but not in others.
 IAFIS- the FBI’s Integrated Automated
Fingerprint Identification system which is a
national database of all 10-print cards from all
over the country
14. What are biometrics and how can they be
used?
• Use of some type of body metrics for the purpose of
identification. (The Bertillon system may actually
have been the first biometry system.)
• Used today in conjunction with AFIS
• Examples include retinal or iris patterns, voice
recognition, hand geometry
• Other functions for biometrics: can be used to
control entry or access to computers or other
structures, can identify a person for security
purposes, can help prevent identity theft or control
social services fraud.
Lab 5 Fingerprinting
15. What are latent prints? What are inked
prints?
• Latent prints- not visible to the naked eye;
must be developed to become visible
• Inked prints- taken from an individual for
identification purposes
16. Why did running one of your thumbs or
fingers down the side of your nose or through
your hair help you make a latent print?
• Pick up secretions from sebaceous glands as
well as eccrine glands.
17. How were latent prints developed with
powder and lifted?
•
•
•
•
•
•
•
•
Dip a soft fingerprint brush into the carbon black or aluminum fingerprint powder.
Then tap it against the top of the powder jar to shake off the excess powder.
With a circular, sweeping motion that barely touches the slide, brush across the
surface until you see the fingerprint begin to appear.
Once you see the fingerprint, apply powder in a direction that follows the ridge
flow.
When the print is clearly developed, stop brushing (or you may destroy the
fingerprint)!
If necessary, carefully shake off any excess powder from the slide over the powder
jar or trash can.
Unwind a piece of clear tape about 10 cm in length and place the free end of the
tape at a point about 7 cm from the top of the print on the slide. Smooth the
piece of tape over the print with your finger, moving slowly from the free end of
the tape to a point about 1 cm past the print.
When the print is entirely covered with tape, pull the whole piece of tape straight
up at once, carefully removing the tape and print from the slide.
Transfer the print to a clean white index card.
18. What are the components of a fingerprint?
19. How are ninhydrin, iodine, and super glue
used to detect latent fingerprints?
• ninhydrin- solution swabbed onto print; reacts
with amino acids to produce a pink/purple
color
• iodine- print placed in fuming jar for 3-5
minutes; reacts with oils to produce
yellow/brown color; then fixed in solution
• super glue- print placed in fuming chamber
for hours; polymerizes on secretions to
produce white print
Chapter 7 The Microscope
20. What are the differences between a simple
microscope, a compound microscope, and a
stereoscope or dissecting microscope?
• simple microscope- one lens
e.g. magnifying lens
• compound microscope- 2 lenses that
“compound” or magnify each other
• stereoscope or dissecting microscope- no special
slide preparation necessary
21. Know the functions and be able to label the
following parts of a compound light microscope:
• eyepiece
– the part of the microscope
you look into
– usually magnifies material
being viewed by 10x
– sometimes contains a
pointer that can be seen as
you look into the eyepiece
– may also be called the
ocular because it contains
the ocular lens
– may be monocular or
binocular
• body tube
- connects eyepiece to
nosepiece
• nosepiece
– part of microscope to
which the objectives are
attached
– rotates to allow for the
changing of objectives to
increase or decrease
magnification
• objectives
- scanning/low (4x)
- medium (10x)
- high (40x)
- oil immersion (60x)
• arm
– a secure part of the
microscope to hold on to
when the microscope is
being carried
• stage
- platform on which
microscope slide rests
• stage clip
• mechanical stage/slide
adjuster
- used for adjusting the
position of the slide for
viewing
• coarse adjustment/focus
knob
- controls large
movements of the
stage
or nosepiece
• fine adjustment/focus
knob
- controls more precise
focusing under higher
powered objectives
• diaphragm
- regulates the
amount of light
passing through the
slide
• illuminator
- light source
• base
- provides support for
microscope
22. Be able to calculate the total magnification
when given the magnification of the ocular lens
and an objective lens.
• Total Magnification = Magnification of Ocular
lens (10x) x Magnification of Objective Lens
23. What is the field of view and how does it
change as magnification increases?
• Field of View (FV) is the
illuminated circle that
you see when looking
through the
microscope.
• As magnification
increases, the size of
the FV gets smaller.
24. Be able to calculate the diameter of a field of
view under a new objective when given the
magnification and diameter of a field of view
under another objective.
• Step 1 Calculate the Increase in Magnification.
New Objective
Old Objective
• Step 2 Divide the old FV by the increase in
magnification calculated in Step 1.
Old FV (microns)
Increase in Mag
25. What is a comparison microscope?
• comparison
microscope- uses two
stages and sets of
objectives connected by
one body tube to one
eyepiece
26. What are electron microscopes?
• electron microscopesuse electrons to
illuminate a specimen
instead of light
- Scanning Electron
Microscope (SEM)
- Transmission Electron
Microscope (TEM)
Chapter 13 Hairs, Fibers and Paint
27. What is a hair follicle?
• Hair grows from a hair
follicle, extending from
its root or bulb, and
continuing into the
shaft before
terminating at the tip.
28. What are the three layers of a hair and
where are they located?
• cuticle- outside
covering formed
by overlapping
scales
• cortex- thickest
layer
• medulla- inner
row of cells
29. What scale patterns are found in the cuticles
of humans and animals?
• imbricate- human, dog
• spinous- rabbit
• coronal- cat
Figure 13-2 Scale
patterns of various
types of hair.
imbricate
spinous
coronal
30. In which part of the hair are pigment
granules embedded?
• cortex- embedded with pigment granules
whose color, shape and distribution provide
important features for comparison
31. What patterns can be found in the medulla?
• medulla- humans may
have a continuous, an
interrupted, a
fragmented, a solid, or
no medulla
Figure 13-4 Medulla
patterns for various
types of hair.
32. How do the medullary indexes differ
between humans and animals?
• The ratio of the diameter of the medulla relative to
the diameter of the whole hair is called the
medullary index (MI).
- Human hair usually has an MI of 1/3 or less.
- Animal hairs usually have an MI of ½ or more.
33. What are the three phases of hair growth
and how do they differ?
• anagen- growth phase that may last up to 6
years; root is attached to the follicle giving it a
flame-shaped appearance
• catagen- hair continues to grow, but at a
decreasing rate for 2-3 weeks; root takes on an
elongated appearance
• telogen- hair growth ends and hair is pushed out
of the follicle over a 2-6 month period; root has a
club-shaped appearance
Figure 13-6 Hair roots in the anagen phase, catagen
phase, and telogen phase.
34. What part of the hair is best for DNA
analysis?
• The follicular tag, when attached to the root,
allows for the best DNA analysis.
35. How does nuclear DNA differ from
mitochondrial DNA?
• nuclear DNA- DNA present
within the nucleus of a cell;
inherited from both parents
- obtained from follicular
tags of hairs in the anagen
or catagen phases
• mitochondrial DNA- DNA
present in organelles called
mitochondria; only
inherited from the mother
- can be obtained from any
hairs 1-2 cm in length
36. How many hairs are needed for a
representative sample of head hair? Of pubic
hair?
• The collection of 50 full-length hairs from all areas of
the scalp will normally ensure a representative
sampling of head hair.
• A minimum collection of 24 full-length pubic hairs
should cover the range of characteristics present in
pubic hair.
37. What is the difference between natural
fibers and manufactured fibers? Be able to
recognize examples of each.
• Natural fibers- derived
from animal or plant
sources
e.g. animal- wool,
cashmere, fur
plant- cotton
Figure 13-8
Photomicrograph of
cotton fiber.
• Manufactured fibersderived from either
natural or synthetic
polymers
e.g. rayon (regenerated
fiber), nylon (synthetic
fibers)
Table 13-1 Major
Generic Fibers
38. What is a monomer? What is a polymer?
• monomer- subunit
• polymer- chain of monomers
Figure 13-10 Starch and cellulose are natural
carbohydrate polymers consisting of a large number of
repeating units or monomers.
39. When can fiber evidence be individual
evidence?
• If the analyst can fit pieces of fiber together at
their torn edges, then the evidence becomes
individual.
40. How can class characteristics obtained from
fibers aid in an investigation like the Wayne
Williams’ case?
• Fibers can be analyzed for characteristics such as
color, cross- section, type and other features.
Figure 13-13 A scanning electron photomicrograph
of the cross section of a nylon fiber removed from a
sheet used to transport the body of a murder
victim. The fiber, associated with a carpet in Wayne
Williams’s home, was manufactured in 1971 in
relatively small quantities.
41. How should fiber evidence be collected and
preserved?
• The investigator’s task of looking for strands of
fibers often becomes one of identifying and
preserving potential “carriers” of fiber evidence.
• Relevant articles of clothing should be packaged
carefully in separate paper bags.
• If it is necessary to remove a fiber from an object,
the investigator must use clean forceps, place it in
a small sheet of paper, fold and label the paper,
and place the paper packet inside another
container.
Lab 6 Examination of Hair and Textile Fibers by
Microscopy
42. Be able to label the medulla, cortex and
cuticle as in Figure 15-1.
43. Be able to identify the scale patterns as in
Figure 15-2.
43. How do human hairs differ from animal
hairs?
• Cuticle scale pattern
- humans- imbricate; animals- imbricate,
spinous or coronal
• Medullary Index
- humans 1/3 or less; animals ½ or more
45. What is the difference between a
longitudinal section and a cross section?
• longitudinal section- view of long axis
• cross-section- view of diameter
Chapter 10 Forensic Serology
46. How many different blood factors have been
identified? Which are the most important?
• There are more than 100 different surface
blood factors.
• The ABO factors are most important for
matching a donor to a recipient.
47. Why is blood important in forensic analysis?
• No two individuals (except identical twins) can
be expected to share all the 100+ blood
factors.
• There is a high frequency of occurrence of
bloodstains at crime scenes, especially crimes
of the most serious nature– that is, homicides,
assaults, and rapes.
48. What are the components of blood?
49. What are the different types of formed
elements found in blood? How do white blood
cells differ from red blood cells?
• platelets- fragments of cells that help repair
damaged blood vessels
• leukocytes- WBCs; responsible for immunity
• erythrocytes- RBCs; biconcave disks that
contain oxygen-carrying hemoglobin protein
- discard their nuclei, mitochondria and most
organelles during development.
50. What are antigens and antibodies?
• antigen- a substance, usually a protein, that
stimulates the body to produce antibodies
against it
• antibody- a protein that binds to a specific
antigen; produced by B lymphocytes
51. Be able to determine the type of blood
based on agglutination.
• The interaction of
antigens on red blood
cells with specific
antibodies carried in
the plasma results in
agglutination, the
clumping together of
red blood cells by the
antibody.
52. What is the Rh factor and how does it
influence blood type?
• The Rh factor was named after the Rhesus
monkey.
• If the Rh factor surface protein is present on
red blood cells, the blood is Rh positive;
otherwise it is Rh negative.
53. What is a gene? What is a chromosome?
• gene- a unit of
inheritance consisting
of a DNA segment
located on a
chromosome
• chromosome- a piece
of DNA wrapped around
various proteins
54. Know the terms karyotype, autosome, and
sex chromosomes.
• karyotype- picture of a
cell’s chromosomes
• Human cells have 46
chromosomes divided into
23 pairs:
- 22 pairs of autosomes
- 1 pair of sex chromosomes
55. Which sex chromosomes are found in
normal females? Normal males?
• XX females
• XY males
56. What are the female and male gametes?
What is a zygote?
• Female gametes, or sex
cells, are called eggs.
• Male gametes are
called sperm.
• At fertilization, the
zygote is formed with
46 chromosomes.
57. What is a locus? What is an allele?
• locus- location of a
gene on a chromosome
• allele- alternative forms
of genes
58. What do the terms homozygous and
heterozygous mean?
• homozygous- an
individual has identical
alleles for a gene
• heterozygous- an
individual has different
alleles for a gene
59. What do the terms dominant and recessive
mean?
• One allele may be
dominant to the other
that is recessive, or
masked.
e.g. Rh + allele is
dominant to Rh - allele
60. What do the terms genotype and phenotype
mean?
• genotype- alleles
present in an individual
• phenotypecharacteristic that
results from genotype
e.g. blood type
61. How does the Kastle-Meyer Color Test
indicate the presence of blood? What are false
positives?
• When blood, phenolphthalein and hydrogen
peroxide are mixed, the hemoglobin in the
blood will turn the normally colorless
phenolphthalein to a bright pink color.
• false positives- materials other than blood
(such as potatoes and horseradish) that also
produce the bright pink positive result
62. What is Luminol? What are the advantages
and disadvantages of using Luminol?
• Luminol is a chemical
that, when mixed with
hydrogen peroxide,
exhibits
chemiluminescence in
the presence of a
catalyst such as the iron
in hemoglobin.
Advantages
• Allows one to detect stains
that would not ordinarily be
visible.
• Extremely sensitive-- can use it
to detect very dilute
concentrations.
• CSIs can spray large areas with
it.
• It does not interfere with DNA,
so a CSI can collect samples for
DNA analysis even after they
were sprayed with luminol.
Disadvantages
• Luminol glows even in the
presence of certain other
fluids-- semen, feces,
bleach, tonic water,
potatoes, etc.
63. How do precipitin and gel diffusion tests
indicate whether blood is from a human or a
specific type of animal?
• Antiserum against the
specific type of blood
(human, deer, dog, etc.)
will react to specific
antigens, forming a
precipitate.
Figure 10-8 Gel Diffusion
Test
64. Can the human immune system naturally
detect the presence of drugs or other
chemicals?
• No.
• The immune system only creates antibodies
and launches attacks against foreign proteins
(either free proteins or ones bound to cells)
and not against other chemical compounds,
like drugs.
65. What is the difference between polyclonal
and monoclonal antibodies? How are each
produced?
• Antigen is injected into an animal such as a rabbit.
• The animal’s immune system will create antibodies
that are specific to the shape of the antigen.
• We can then isolate these antibodies from the
animal’s blood serum.
• polyclonal antibodies- antibodies that bind to a
variety of sites on an antigen
• monoclonal antibodiesantibodies that all recognize
a single site on an antigen
• A mouse is immunized
against a specific antigen
and then its spleen cells are
fused with myeloma
(cancer) cells.
• Clones, groups of identical
cells, are grown and each
produces one type of
monoclonal antibody.
66. What is EMIT and how is it used to detect
marijuana metabolites in blood?
• Enzyme-Multiplied Immunoassay Technique (EMIT)
• Monoclonal antibodies for THC-9-carboxylic acid are added to the
sample to be tested (blood, urine).
• The antibodies will immediately bind to any THC-9-carboxylic acid
molecules present in the sample.
• Enzyme-labeled THC-9-carboxylic acid molecules are then added to
the sample.
• Any antibodies that did not bind to THC-9-carboxylic acid prior to
this step (extra antibody molecules), will bind to the enzymelabeled THC-9-carboxylic acid.
• One can now measure the amount of unbound or unused enzymelabeled THC-9-carboxylic acid to get a value of THC originally
present in the sample.
• more unbound enzyme-labeled THC-9-carboxylic acid = more THC9-carboxylic acid originally present in sample
67. What is acid phosphatase and why is it used
to detect semen?
• Acid phosphatase is an enzyme secreted by the
prostate gland into seminal fluid, where its
concentration is 400x greater than those found in other
body fluids.
• When acid phosphatase comes in contact with a
solution of sodium alpha napthylphosphate and Fast
Blue B, a purple color appears.
• However, some substances, including cauliflower,
watermelon, fungi, contraceptive creams and vaginal
secretions also give positive acid phosphatase results,
though usually not as quickly or strongly.
68. What is oligospermia? What is aspermia?
• oligospermia- males
with abnormally low
sperm counts
• aspermia- males who
do not produce sperm
69. What evidence is collected from a victim as
part of a rape kit?
• Appropriate items of physical evidence
including clothing, hairs, and swabs can be
collected for subsequent laboratory
examination.
• All outer and under garments should be
carefully removed and packaged separately in
paper (not plastic) bags.
• Bedding, or the object upon which the assault
took place, may also be carefully collected.
70. How does Locard’s exchange principle
influence rape evidence?
• The forceful physical contact between victim
and assailant may result in a cross-transfer of
such physical evidence as blood, semen,
saliva, hairs, and fibers.
• If a suspect is apprehended within 24 hours of
the assault, it may be possible to detect the
victim’s DNA on the male’s underwear or on a
penile swab from the suspect.
Chapter 12 Crime-Scene Reconstruction:
Bloodstain Pattern Analysis
71. How does surface texture influence
bloodstains? What is satellite spatter?
• The harder and less porous the surface, the
less spatter that results.
• satellite spatter- small droplets of blood that
are distributed around the perimeter of a
drop or drops of blood and were produced
as a result of the blood impacting the target
surface
Figure 12-2 Bloodstain on glass surface versus
cotton sheet.
72. How is the direction of travel determined
from a bloodstain?
• The pointed end of a bloodstain faces its
direction of travel.
Figure 12-3 Bloodstain pattern produced by
drops of blood traveling from left to right.
73. How does the angle of impact influence
bloodstains?
• A drop deposited at an
angle of 90°, directly
vertical to the surface,
will be approximately
circular in shape.
• As the angle of impact
deviates from 90°, the
stain becomes more
elongated.
Figure 12-4
74. How are the areas of convergence and origin
determined from bloodstains?
• If you draw straight
lines through the long
axis of several blood
stains, you can
determine the area of
convergence.
• The area of origin may
further be determined
by considering the
angle of impact.
Figure 12-8
75. How do bloodstains resulting from arterial
gush or spurt often appear?
• Bloodstains resulting from blood exiting the
body under pressure from a breached artery
often show a pattern related to the heart
beat.
76. How do cast-off stains often appear and
what can they reveal about a crime?
• Blood released or thrown from a blood-bearing object in
motion (e.g. knives, bludgeons) often appears in an arc.
• Can reveal whether assailant used left or right hand and how
many times victim was struck.
77. What is impact spatter?
• impact spatter- bloodstain patterns produced
when an object makes forceful contact with a
source of blood, projecting drops of blood
outward from the source
78. What is the difference between forward and
back spatter?
• forward spatter- blood that travels away from
the source in the same direction of the force
that caused the spatter
• back spatter- blood directed back toward the
source of the force that caused the spatter
79. How do low-velocity, medium-velocity and
high-velocity impact spatter differ?
• low velocity- created by a force travelling at 5
feet/sec or less; produces relatively large stains
greater than 4 mm in diameter
• medium velocity- created by a force travelling at
5- 25 feet/sec; produces stains 1 – 4 mm in
diameter; normally associated with blunt-force
trauma
• high velocity- created by a force travelling at 100
feet/sec or greater; produces stains with
diameters less than 1 mm; normally associated
with gunshot exit wounds or explosions
80. What is a transfer bloodstain and what can it
reveal about a crime?
• A transfer bloodstain is
created when a wet,
bloody surface comes in
contact with a secondary
surface.
• A recognizable image of
all or a portion of the
original surface may be
observed in the pattern,
as in the case of a bloody
hand or footwear print.
Lab 7/8 Blood
81. What is the difference between a
presumptive test and a confirmatory test?
• Initial tests are called presumptive tests because of
their potential results. Presumptive tests can, at best,
only strongly indicate that the tested substance is
correctly assumed because other substances can also
give a positive result.
• Confirmatory tests do not usually give false
positives. It is only after you have a positive result
from a confirmatory test that you can make a
positive identification of the substance.
82. Be able to interpret the results of a KastleMeyer Test.
• clear- negative
• pink, within 10 sec- positive for blood
• color change earlier or later- false positive
83. Be able to interpret the results of a blood
typing test.
• When antibody binds antigen, agglutination (clumping)
results.
• No clumping indicates antibody does not bind to
antigen.
Type A blood clumps in anti-A serum
Type B blood clumps in anti-B serum
Type AB blood clumps in both anti-A and anti-B
sera
Type O blood does not clump in either anti-A or anti-B
sera
84. How does Luminol detect the presence of
blood?
• Traces of blood can be detected when Luminol
is prepared with hydrogen peroxide as a basic
solution. When a catalytic amount of iron is
provided from the hemoglobin in blood it will
generate the blue chemical glow that is
described as chemiluminescence.
85. How is the impact angle of blood calculated?
width of stain = sine of the impact angle
length of stain