Transcript BLOOD AND BLOODSTAINS

BLOOD AND
BLOODSTAINS
Introduction to Blood
Introduction to Blood
What you should already know:
It’s that red stuff that comes out of your
fingers following a kitchen accident.
Introduction to Blood
Blood Facts
The average adult has about FIVE liters of blood inside of
their body, which makes up 7-8% of their body weight.
Blood is living tissue that carries oxygen and nutrients to
all parts of the body, and carries carbon dioxide and other
waste products back to the lungs, kidneys and liver for
disposal. It also fights against infection and helps heal
wounds, so we can stay healthy.
There are about one billion red blood cells in two to three
drops of blood. For every 600 red blood cells, there are
about 40 platelets and one white cell.
http://www.bloodbankofalaska.org/about_blood/index.html
Introduction to Blood
Red Blood Cells = No DNA
White Blood Cells = DNA in nucleus
Introduction to Blood
White Blood Cells = DNA in nucleus
Introduction to Blood
 RBC = no DNA; WBC = yes DNA
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All blood cells have blood groups on
outside of cell.
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Red Blood Cells contain the protein
hemoglobin, which carries oxygen
Introduction to Blood
ABO blood groups found on outside of cell
Hemoglobin picks up and drops off oxygen
Unknown Stain at a Scene
Questions to be answered:
 Is it blood?
 Is it human blood?
 Whose is it?
 Determine blood type, alcohol
content, drugs present
 Determine the method(s) in which
blood may have been deposited
Forensic Analysis of Blood
1. Visual examination of evidence
2.
Presumptive screening test (Is it blood?)
3.
Confirmation test (Seriously, is it blood?)
4.
Determine species origin (human blood?)
5.
Identify the blood (whose blood is it?)
Forensic Analysis of Blood
1. Visual examination of evidence
2.
Presumptive screening test (Is it blood?)
3.
Confirmation test (Seriously, is it blood?)
4.
Determine species origin (human blood?)
5.
Identify the blood (whose blood is it?)
Presumptive Screening Tests
 Negative result means the questioned stain is not likely
blood
 Positive result means the questioned stain is likely blood
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Presumptive tests produce a color reaction or release of
light
Tests rely on catalytic properties of blood (hemoglobin
presence)
Three Categories
 Color
 Luminescent
 Fluorescent
Presumptive Screening Tests
Color Tests
 Apply chromogen (color
changing chemical)
 Apply oxidizing agent
(hydrogen peroxide)
 The catalyst of the reaction is
hemoglobin
Rapid color change is a positive result.
This means the stain is blood.
Presumptive Screening Tests
Color Tests
Remember, other non-blood substances
might catalyze the reaction also.
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Chemical Oxidants
 Plant materials
False Positive – A positive result given by a
substance that is not blood.
Screening Tests
 Based on the “peroxidase-like” activity of the
blood
Linked to the hemoglobin’s heme portion
 Basic reaction:
H2O2 + Heme  2[OH-]
Colorless substrate + 2[OH-]  Colored product + 2H2O
Screening Tests
 Extremely Sensitive
Presence of blood detectable even when there is
no visible staining
 EX: phenolphthalein – can detect 1 part blood in 1-10
million parts of dilutent
 Kastle-Meyer Color Test Mixture of
phenolphthalein and hydrogen peroxide on
blood cause the mixture to turn pink
Because hemoglobin reacts like a peroxidase
(enzyme that breaks down hydrogen peroxide),
reaction will give off oxygen in presence of
hydrogen peroxide
Hematest® Tablet
 reacts with the heme group in blood causing
a blue-green color
TMB
Tetramethylbenzidine (TMB)
 Positive result = Blue-green
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Most common test for blood
1. Rub stain with moist swab
2. Add TMB
3. Add peroxidase
Look for quick blue color
TMB
Tetramethylbenzidine (TMB)
 Positive result = Blue-green
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Most common test for blood
1. Rub stain with moist swab
2. Add TMB
3. Add peroxidase
Look for quick blue color
Presumptive Screening Tests
Chemiluminescence and Fluorescence
 More sensitive than color tests
 May damage blood stain (no blood/DNA typing)
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Used to locate and define areas of blood
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old blood stains
 cleaned floor
Presumptive Screening Tests
Luminol
 Method similar to color
test
 Luminol is combined
with oxidant and
sprayed over area
thought to contain blood
 Emits a blue-white to
yellow green glow
 Destroys important
markers for DNA
fingerprinting
Presumptive Screening Tests
Fluorescein
 Fluorescein is combined
with oxidant and sprayed
over area thought to contain
blood
 Fluoresces when treated with
a UV light
 Fluorescein includes a
thickener; this makes it more
effective on vertical surfaces
 Study showed no interference
with DNA analysis
Forensic Analysis of Blood
1. Visual examination of evidence
2.
Presumptive screening test (Is it blood?)
3.
Confirmation test (Seriously, is it blood?)
4.
Determine species origin (human blood?)
5.
Identify the blood (whose blood is it?)
Confirmatory Tests
 Due to the possibility of false positives with the
presumptive tests, confirmatory tests are
necessary
 Confirmatory tests involve making crystals that
detect the presence of hemoglobin
 Teichmann Test and Takayama Test
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Small amount of blood added to microscope slide
Chemical solution is added
Slide is heated to form crystals
Crystals viewed under microscope
Forensic Analysis of Blood
1. Visual examination of evidence
2.
Presumptive screening test (Is it blood?)
3.
Confirmation test (Seriously, is it blood?)
4.
Determine species origin (human blood?)
5.
Identify the blood (whose blood is it?)
Species Origin
Most methods test for serum proteins
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Serum proteins are found in all animals,
but are slightly different
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Species ID methods based on
antigen/antibody interactions
Microscopic
Views
Fish Blood
Bird Blood
Horse Blood
Frog Blood
Cat Blood
Dog Blood
Human Blood
Snake Blood
Species Origin
 Antigen = serum protein
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Antibody = produced when foreign serum
protein is detected
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Certain antibody will only attach to one
species’ serum protein
Species Origin
Antibody is
in antiserum
Antigen (serum protein)
is in blood sample
 Human antiserum will only attach to human blood sample
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Rabbit antiserum will only attach to rabbit blood sample
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Dog antiserum will only attach to dog blood sample
Species Origin
Ring Precipitin Test
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Blood sample (dilute)
in top layer
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Antiserum in heavy
bottom layer
Species Origin
Ring Precipitin Test
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Blood sample (dilute)
in top layer
Precipitate means blood and
antiserum species match
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Antiserum in heavy
bottom layer
Species Origin
Ring Precipitin Test
Yes line = Yes human blood
Human Antiserum
Species Origin
Ring Precipitin Test
No line = Not human blood
Human Antiserum
Anti-human test
 Human blood is injected into an animal
 Usually a rabbit
 Animal will produce antibodies against human blood
 Serologist will extract antibodies from the
rabbit’s serum
Called Human anti-serum
Anti – Human Test
 Layer an extract of the blood stain on top of
the human anti-serum in a capillary tube
If blood is human, there will be a reaction
between the human anti-serum and the unknown
blood and a precipitate will form
Precipitin test
 An antibody that reacts
with its corresponding
antigen will be used on
the unknown stain to
see if it will precipitate
(solidify or crystallize)
False positives
 Contamination of the blood sample
 Blood is from higher order apes
 Close relatives of humans
 Orangutan
 Chimpanzee
 Gorilla
Other origin tests
 Gel diffusion
Same basic technique as a precipitin test except it
is done in a gel plate
 Antigens and antibodies will be attracted towards
each other
 Electrophoretic method
Apply an electrical charge to accomplish same
results
Secretor
 An individual who secretes his or her blood-
type antigen in body fluids
 Found saliva, semen, vaginal secretions, gastric
juices
Approximately 85% of people are secretors
Forensic Analysis of Blood
1. Visual examination of evidence
2.
Presumptive screening test (Is it blood?)
3.
Confirmation test (Seriously, is it blood?)
4.
Determine species origin (human blood?)
5.
Identify the blood (whose blood is it?)
Genetic Markers in Blood
If a stain is blood, and it is human blood, then
whose is it?
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Blood Group Markers
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Protein/Enzyme Markers
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DNA
Blood Group Markers
Many blood group markers, including:
 ABO Markers
 Lewis System
 Rhesus System
Blood Group Markers
ABO Markers
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Look at antigens on Red Blood Cells
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In this case, antigens are glycoproteins
and are attached to the outside of the cell
Blood Terminology
 ABO blood groups based on having an A, B, both or
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no antigens on red blood cells
Rh factor may be present on red blood cells; positive
if present and negative if not
Antigen  a substance that can stimulate the body to
make antibodies. Certain antigens (proteins) found in
the plasma of the red blood cell’s membrane account
for blood type.
Antibody  a substance that reacts with an antigen
Agglutination  clumping of red blood cells; will
result if blood types with different antigens are mixed
Introduction to Blood
ABO blood groups found on outside of cell
Blood Group Markers
ABO Markers (antigen and antibodies)
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A person will have antibodies (A or B) to
whatever blood group he/she doesn’t
have
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Otherwise, a persons blood would clump
up and cause death
Genetics of Blood Types
 Your blood type is established before you are BORN,
by specific GENES inherited from your parents.
 You inherit one gene from your MOTHER and one
from your FATHER.
 These genes determine your blood type by causing
proteins called AGGLUTINOGENS to exist on the
surface of all of your red blood cells.
What are blood types?
Blood Types
There are 3 alleles or genes for blood
type: A, B, & O. Since we have 2 genes,
there are 6 possible combinations.
AA or AO = Type A
BB or BO = Type B
OO = Type O
AB = Type AB
http://learn.genetics.utah.edu/units/basics/blood/types.cfm
Blood Group Markers
ABO Markers
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A cells clump with anti-A
B cells clump with anti-B
AB cells clump with both
O cells do not clump
Blood Transfusions
A blood transfusion is a procedure in which blood is given to a patient through an
intravenous (IV) line in one of the blood vessels. Blood transfusions are done to replace
blood lost during surgery or a serious injury. A transfusion also may be done if a person’s
body can't make blood properly because of an illness.
Who can give you blood?
Universal Donor
People with TYPE O blood are called
Universal Donors, because they can give
blood to any blood type.
People with TYPE AB blood are called
Universal Recipients, because they can
receive any blood type.
Rh +  Can receive + or Rh -  Can only receive Universal Recipient
Rh Factors
 Scientists sometimes study Rhesus monkeys
to learn more about the human anatomy
because there are certain similarities between
the two species. While studying Rhesus
monkeys, a certain blood protein was
discovered. This protein is also present in the
blood of some people. Other people, however,
do not have the protein.
 The presence of the protein, or lack of it, is
referred to as the Rh (for Rhesus) factor.
 If your blood does contain the protein, your
blood is said to be Rh positive (Rh+). If your
blood does not contain the protein, your blood
is said to be Rh negative (Rh-).
http://www.fi.edu/biosci/blood/rh.html
A+ AB+ BAB+ ABO+ O-
Blood Evidence
 Blood samples – Can be analyzed to determine blood
type and DNA, which can be matched to possible
suspects.
 Blood droplets – Can be analyzed to give clues to the
location of a crime, movement of a victim, and type
of weapon.
 Blood spatter – Can be analyzed to determine
patterns that give investigators clues to how a crime
might have happened.
Blood Group Markers
ABO Markers (antigen and antibodies)
Blood Type Antigen
(blood group)
A
B
AB
O
Antibody
% population
Blood Group Markers
ABO Markers (antigen and antibodies)
Blood Type Antigen
Antibody
% population
(blood group)
A
B
AB
O
A
Anti-B
40
Blood Group Markers
ABO Markers (antigen and antibodies)
Blood Type Antigen
Antibody
% population
(blood group)
A
A
Anti-B
40
B
B
Anti-A
10
AB
O
Blood Group Markers
ABO Markers (antigen and antibodies)
Blood Type Antigen
Antibody
% population
(blood group)
A
A
Anti-B
40
B
B
Anti-A
10
AB
A&B
none
5
O
Blood Group Markers
ABO Markers (antigen and antibodies)
Blood Type Antigen
Antibody
% population
(blood group)
A
A
Anti-B
40
B
B
Anti-A
10
AB
A&B
none
5
O
H
Anti-A &
Anti-B
45
How common is your blood type?
46.1%
38.8%
11.1%
3.9%
Blood Group Markers
ABO Markers
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Testing is similar to species test
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An anti-A, anti-B, or anti-AB antiserum
(containing antibodies) is reacted with the
blood stain to detect blood cells
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A, B, or AB blood cells are reacted with a
blood stain to detect antibodies
Blood Group Markers
ABO Markers
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Tests can get complicated with absorbing
and releasing cells
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Final step is usually testing for
agglutination (blood clumping)
Other Markers
Protein or Enzyme Markers
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Some proteins or enzymes can be in
different forms (different shapes)
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These differences can be detected by
separating the proteins in a gel by
electrophoresis
Protein or Enzyme Markers
+
 Charge makes proteins
move through gel
 Different shapes move at
different rates
 After several minutes, their
location will tell what type
they are.
-
Ladder Type 1 Type 2 Type 3
Protein or Enzyme Markers
Genetic Markers in Blood
 ABO blood typing and protein analysis may help
eliminate a suspect.
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Since there are only a small number of
types (ABO = 4 types), a match does not
mean the stain definitely came from a
certain person
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DNA testing can identify a person, and is
becoming just as easy as the above tests