Download Forensic Serology

Forensic Serology
“Out damned spot! Out, I say
Here’s the smell of the blood still,
All the perfumes of Arabia will not
Sweeten this little hand. Oh, Oh, Oh!”
—William Shakespeare’s Lady Macbeth, in Macbeth
Using Blood in Forensics
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Test for blood type
Provides DNA evidence
Analyze bloodstains
Blood spatter patterns
Livor mortis- pooling of blood in dead
organisms
Karl Landsteiner
• In 1901 he discovered that all humans do not
have the same blood type
• He discovered the A-B-O blood group system
• This saved millions of lives by preventing
mismatched blood transfusions
• Other researchers were able to discover the
Rh factor because of his research
• 29 years later, they gave Karl a Nobel Prize
Serology
Serology is the examination and analysis of body
fluids. A forensic serologist may analyze a variety
of body fluids including saliva, semen, urine, and
blood. From 1950 to the late 1980’s, forensic
serology was a most important part of lab
procedures. With the development of DNA
techniques, more time, money, and significance
was placed in developing DNA labs. However,
with limited funds and the time required for
DNA testing, most labs still use many of the basic
serology testing procedures.
Blood and Forensics
• No 2 individuals
(except identical
twins) can share all
the 100+ blood
factors
• So forensic scientists
used this tool to link
blood from a crime
scene to an
individual
Role of blood in the human body
1. Blood is a fluid connective tissue
2. Transportation
It transports oxygen, carbon
dioxide, nutrients, wastes, water,
ions, and minerals
Role of blood in the human body
3. Regulation
Hormones (to regulate body
functions)
Heat (to regulate body temperature)
4. Protection
– Clotting protects against blood loss
– Provides immunity to many
diseases
What is Blood?
3 Cell Types + Fluids:
• Erythrocytes (Red
Blood Cells)
• Leukocytes (White
Blood Cells)
• Platelets (Cell
fragments)
• Plasma
White Blood Cell
Platelets
Red Blood Cells
Characteristics of Red Blood Cells
• Red blood cells (erythrocytes) are
biconcave disks that contain the
oxygen-carrying protein hemoglobin.
Characteristics of Red Blood Cells
• In addition to 100s of cell surface proteins,
their cell surfaces have a special class of
blood factor proteins called Antigens.
• There are at least 15 different antigens, but
the most important are the ABO and Rh
antigens
Role of RBCs
• Transport inhaled O2 from lungs to all body cells
– O2 + hemoglobin = bright red blood
• Remove CO2 from all body cells and take it back
to lungs for exhalation
– CO2 + hemoglobin = dark red blood
• RBCs are destroyed after about 120 days
– Broken down by the liver
Oxygen rich blood vs Oxygen poor blood
Summary of Functions of WBCs
Leukocytes can squeeze between cells lining
walls of blood vessels and attack bacteria and
debris.
• Neutrophils and monocytes are phagocytic
(cell killers).
• Eosinophils moderate allergic reactions as
well as defend against parasitic infections.
• Basophils migrate to damaged tissues to
promote inflammation and to inhibit blood
clotting.
• Lymphocytes are the major players in specific
immune reactions and some produce
antibodies (Ex: T cells and B cells)
Summary of Functions of WBCs
Blood Platelets (Thrombocytes)
• Blood platelets are fragments of cells
• Platelets help repair damaged blood vessels
by adhering to their broken edges.
• Thrombopenia, or low platelet counts
increase bleeding risks
• Thrombocytosis or high platelet count may
lead to thrombosis (clotting, bruising,
strokes, heart attacks).
Blood Platelets (Thrombocytes)
Blood Clotting
• The blood clots when the protein
FIBRIN traps and meshes RBCs
together.
• SERUM is a yellow liquid that
remains after the RBCs clot.
Clotting
Blood Clotting – Fibrin Net
Blood Clotting and Forensics
• The clotting process begins 3-15 minutes from
injury.
– 1st forms dark, shiny, jelly-like mass
– 2nd begins to contract and separate from serum.
• How long ago did the victim begin bleeding?
– A few minutes: Blood is still liquid
– Less than an hour: Blood is shiny, gelantinous, in a
pool.
– Several hours: Blood has separated into clot and
serum
Hematocrit
Hematocrit means the
percentage of red
blood cells in blood.
Scientists use a
centrifuge to separate
the parts of blood
based upon density
of the parts.
• A blood hematocrit is normally 45% cells and 55% plasma.
Blood Plasma
• Plasma is the clear, strawcolored fluid portion of
the blood.
• Plasma is mostly water,
with a mixture of, amino
acids, proteins,
carbohydrates, lipids,
vitamins, hormones,
electrolytes, and cellular
wastes.
Hematocrit
• The liquid plasma
is separated by
the solid RBCs by
the Buffy Coat
layer.
Buffy Coat?
Buffy coat is the layer that contains
most of the white blood cells and
platelets.
“Buffy” because it is buff in color
The buffy coat is used to extract DNA
from blood - RBCs have no DNA (no
nucelus), only WBCs do (they have 1+
nuclei).
ABO Blood Group
• Antigens are on red blood cells and
antibodies are in the plasma.
ABO Blood Group
• Antigens are on red blood cells and
antibodies are in the plasma.
• Adverse transfusion reactions are avoided by
preventing the mixing of blood that contains
matching antigens and antibodies.
– Adverse reactions are due to the
agglutination of red blood cells.
Blood Groups and Transfusions Antigens
and Antibodies
• Clumping of red blood cells following transfusion is
called agglutination.
• Agglutination is due to the interaction of proteins
on the surfaces of red blood cells (antigens) with
certain antibodies carried in the plasma.
Rh Blood Group
• 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.
• There are no corresponding antibodies in the plasma
unless a person with Rh-negative blood is transfused
with Rh-positive blood; the person will only then
develop antibodies for the Rh factor.
Blood Groups
Antibody Can Give
Can Get
Blood From
Type
Antigen
A
A
B
A, AB
O, A
B
B
A
B, AB
O,B
AB
A and B
Neither
A nor B
AB
A, B, O, AB
O
Neither
A nor B
A and B
A, B, O, AB
O
Blood To
Universal Donor is O, Universal Recipient is AB.
Agglutination of RBCs
Population Distribution
of Blood Types in the U.S.
Type
Percent
O
45
A
40
B
11
AB
4
Relative Frequency of Blood Types in
Human Populations
Population
US whites
US blacks
Chinese
Eskimos
Armenians
Bolivian
Indians
O
.453
.491
.439
.472
.298
.931
A
.413
.265
.270
.452
.499
.053
B
.099
.201
.233
.059
.132
.016
AB
.035
.043
.058
.017
.080
.001
• Genotype: describes the allelic pair
combination
• Phenotype: describe the trait/characteristic
expressed
Genetic Blood Typing (Genotypes)
Mother
Father
A
B
O
A
AA
AB
AO
B
AB
BB
BO
O
AO
BO
OO
Transmission of our traits
Allele
Combinations
Blood Type
(phenotype)
AA + AO
A
BB +BO
B
AB
AB
OO
OO
Paternity Testing
• Human leukocyte antigen (HLA) is used in
paternity testing.
• If a man and child share the HLA markers
there is a 90% probability that the man is the
child’s father.
• The Haptoglobin marker + ABO + HLA
increases the probability to 95%
DRUG - DETECTION
Hypothesis:
Since foreign substances in blood are identified and
then isolated by the immune system, it should be
able to detect the presence of drugs and other
chemicals.
This hypothesis is incorrect. 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.
We can fool the immune
system
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The drug can be attached to a carrier molecule that is a
protein
This drug-protein combo can be injected into an animal
such as a rabbit or rat (no human volunteers)
The animal’s immune system will create antibodies that
are specific to the shape of this drug-protein combo
molecule
We can isolate these antibodies from the animal’s blood
serum
And use these antibodies to detect the presence of the
drug in human blood or urine
Now how does a criminalist use these
antibodies?
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To detect drug presence in blood, urine, etc.
A.K.A. EMIT assays (bio jargon for test)
EMIT stands for Enzyme-multiplied
Immunoassay Technique
EMIT is most often used to test for marijuana
(THC) metabolites in urine.
One of the primary THC metabolites is THC9-carboxylic acid
Questions for a Criminalist:
1. Is it blood?
2. Is it human blood?
3. If it is human, can it be linked to a suspect /
victim and how closely?
The Kastle-Meyer Test to ID Blood
(tests for hemoglobin)
• Phenolphthalein = colorless
• Blood+ phenolphthalein + hydrogen peroxide
= bright pink because of hemoglobin
• This test can yield some false positives
• Certain vegetable matter can produce the
bright pink positive (such as potatoes)
Death By Potato?
• Although the KastleMeyer test can give a
false positive in the
presence of certain
plant matter, it is
unlikely that this plant
matter would be
present at a crime
scene and be mistaken
for blood.
Other blood detection tests
• Doctors use Hemastix© strips to detect blood
in urine, but these strips can be used at a
crime scene to detect fresh or dried blood.
• Moisten them with distilled water and wipe
the bloodstain. A color change to green is a
positive indicator of blood
Bayer Hemastix©
Luminol
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Luminol is a chemical that exhibits chemiluminescence,
with a striking blue glow, when mixed with an
appropriate oxidizing agent. It is a white to slightly
yellow crystalline solid that is soluble in water and most
polar organic solvents.
Usually, a solution of hydrogen peroxide (H2O2) and a
hydroxide in water is used as the activator.
In the presence of a catalyst such as an iron compound,
the hydrogen peroxide is decomposed to form oxygen
and water:
What do you see with luminol?
It glows a bright blue in the dark, when it comes in contact with bloo
Advantages of using Luminol
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Allows one to detect stains that would not be
ordinarily be visible
Extremely sensitive - can use it in very dilute
concentrations
This allows the CSI to spray large areas with it
It does not interfere with DNA, so a CSI can
collect samples for DNA analysis even after it
was sprayed with luminol.
Bloody Footprints that were wiped
Drawbacks
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Luminol glows even in the
presence of certain other
fluids – semen, feces,
bleach, tonic water, etc.
Luminol glows in the
presence of certain
vegetable matter - Mr.
Potato head strikes again!
Thanks to Quinine
So we know its blood – but is it human?
• The Precipitin Test
– Rabbits injected with human blood
– They make antibodies in their serum
– They are bled and the serum recovered
– The serum is called human antiserum,
because it will react to human antigens
– It will cause coagulation when mixed with
human blood
Precipitin Test
(Human blood)
(Human antiserum
made in rabbits)
Is it human blood?
• Human Blood
• Frog Blood
Gel Diffusion Test
• Antigen (blood) and antibodies (human
antiserum from rabbits) are placed in separate
wells in a gel.
• They are forced to move towards each other. If
they bind to each other, they form a single line
of precipitate in between the wells
• This is a positive for human blood
DNA TEST
• DNA testing is the ultimate for learning as
much as possible about a blood sample.
• It has made many other tests obsolete.