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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
Chapter 10
Using Blood in Forensics
 Test for blood type
 Provides DNA evidence
 Analyze bloodstains
 Blood spatter patterns
 Livor mortis- pooling of blood in dead
organisms
Chapter 10
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
Chapter 10
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.
Chapter 10
Blood and Forensics
Chapter 10
 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
 3. Regulation
 Hormones (to regulate body functions)
 Heat (to regulate body temperature)
 4. Protection
 Clotting protects against blood loss
 Provides immunity to many diseases
Chapter 10
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
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 (T cells and B cells)
Blood Platelets

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 Clotting
The blood clots when
the protein FIBRIN
traps and meshes
RBC’s together.
 SERUM is a yellow
liquid that remains
after the RBC’s clot.

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,
straw-colored fluid portion
of the blood.
• Plasma is mostly water,
with a mixture of, amino
acids, proteins,
carbohydrates, lipids,
vitamins, hormones,
electrolytes, and cellular
wastes
Buffy Coat?
Buffy coat is the layer that contains most of
the white blood cells and platelets.
“Buffy” because it is buff (color of naked skin)
in color
The buffy coat is used to extract DNA from
blood - RBCs have no DNA, only WBCs do.
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





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?





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.
2.
3.
Is it blood?
Is it human blood?
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



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




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


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.
