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FORENSIC SCIENCE
Serology
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What is forensic serology?
Forensic serology- is the study of blood
serum, along with saliva, semen and other
bodily fluids found at a crime scene.
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Blood Characteristics
• Plasma--fluid portion of the blood (55%)
• Cells (45%)
– Erythrocytes--red blood cells; responsible for
oxygen distribution
– Leukocytes--white blood cells; responsible for
“cleaning” the system of foreign invaders
– Thrombocytes--platelets; responsible for blood
clotting
• Serum--liquid that separates from the blood when
a clot is formed
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Blood components
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In addition, blood has:
•Water
•Cells
•Enzymes
•Proteins
•Other inorganic substances
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Blood components
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Blood
Questions to be answered:
• Is it blood?
• Is it human blood?
• Whose is it?
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Presumptive Tests for
Blood
• Kastle-Meyer color test--phenolophthalein
and hydrogen peroxide are mixed together the
blood’s hemoglobin will cause the formation of a
deep pink color.
• Leucomalachite test--leucomalachite green
mixed with acetic acid and distilled water; then a drop
of sodium perborate will turn blood green and then
darken.
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Other Tests for Blood
• Luminol test--reaction with blood results in
the production of light.
• Microcrystalline tests--add specific
chemicals to the blood in order to form
characteristic crystals
– Takayama
– Teichmann
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Human vs. Animal Blood
• Microscopic analysis
• Precipitin test
– blood is injected into a rabbit
– anti-human antibodies are formed
– anti-human antibodies which are then extracted from
the rabbit's serum
– If this antiserum is then placed on a sample from the
crime scene, and the blood displays clotting, the
forensic investigator can conclude that the blood is
human blood.
– precipitin line forms if sample is human blood
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Bloodstain Analysis:
Animal Blood?
*precipitin line forms if sample is human blood
Is It Human?
Microscopic Analysis
Frog Blood
Human Blood
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Historical Perspective
Of Blood Typing
1901- Karl Landsteiner: ABO typing based on
antigen-antibody reaction.
1915- Leone Lattes: applied ABO typing to
dried stains
1940- Landsteiner and Weiner: Rh factor
85% of Caucasians, 94% of Black Americans
and 99% of Asians are Rh positive.
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Blood Grouping
During the late 1930s, a series of antigen-antibody
reactions were discovered in blood, the most
common ones being ABH, MN, Rh, and Gm.
There are more than 256 antigens, and twenty-three
blood group systems based on association with
these antigens. A fundamental principle of serology
is that for every antigen, there exists a specific
antibody. In fact, all blood groups are defined by the
antigens on their red blood cells and the antibodies
in their serum.
Rh Factor (antigen in serum)
Blood can also be categorized
using the Rh (Rhesus disease)
factor.
If an individual has a positive Rh
factor, this means that his/her
blood contains a protein that is
also found in Rhesus
monkeys.
Approximately 85% of the
population has a positive Rh
factor, and doctors are trained
to monitor closely any woman
who is Rh negative and
becomes pregnant.
When a Rh(-) woman becomes
pregnant with Rh(+) child, the
woman's body might naturally
produce antibodies that attack the
baby's blood, he result of this
incompatibility will not affect the
health of the mother, but it can
affect the child's health. Potential
health problems include jaundice,
anemia, and brain or heart
damage. In severe cases, Rh
disease can kill the baby.
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Nature of Blood: Antigens in
Red Blood Cells
Red blood cells have antigens on
their surface. An antigen is a
substance that when introduced
into the body stimulates the
production of an antibody.
Antigens include toxins,
bacteria, foreign blood cells,
and the cells of transplanted
organs.
RBC: Antigens
Prior to birth, your lymphocytes learn which
cells belong as part of your body, and see
those as non-antigenic or safe. Your
immune system recognizes "you" and does
not try to destroy those cells. This is called
immunotolerance.
Any new substance noted by the immune
system will be considered an invader and
destroyed.
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Blood types
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Nature of Blood: Serum
-yellow hue
-contains white blood cells and platelets
-determine the freshness of a blood
sample by examining serum because it
clots several minutes after exposure to
air.
-in addition, serum contains antibodies,
proteins floating in blood fluid. The
purpose of an antibody is to identify and
neutralize antigens so that they cannot
make the host organism sick.
Blood Typing
Blood typing requires two antiserums: anti-A and anti-B.
By inserting a droplet of these antiserums in samples of
blood, one can determine which samples maintain a
normal appearance and which samples become clotted,
or agglutinated, under microscopic examination.
Type-A blood will be agglutinated by anti-A serum;
Type-B blood will be agglutinated by anti-B serum;
Type-AB blood by both; and
Type-O blood by neither.
Blood Groups
Type
Antigen
Antibody
Can Give
Blood To:
Can Get
Blood From
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
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Blood Reactions to Antiserum
REACTION
Anti-A Serum
Agglutination
Anti-B Serum
No agglutination
No agglutination Agglutination
Agglutination
Agglutination
No agglutination No agglutination
BLOOD TYPE
Type A
Type B
Type AB
Type O
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Population Distribution
of Blood Types in the U. S.
Type
Percent
O
45
A
39
B
12
AB
4
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Differentiating Blood Types
ABO and Rh factors
Iso-enzymes: Enzymes that exist in
different forms are called polymorphic
and can be broken down into their
separate proteins.
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Commonly Used
Blood Enzymes and Proteins
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Adenosine deaminase
Adenylate kinase
Carbonic anhydrase II
Erythrocyte acid phosphatase
Esterase D
Glucose-6-Phosphate dehydrogenase
G6PD
Glyoxylase U
Group-specific component
Ge
Haptoglobin
Peptidase A
Phosphoglucomutase
6-Phosphogluconate dehydrogenase
6PGD
Transferrin
AD
AK
CA II
EAP
EsD
GLO I
Hp
Pep A
PGM
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Tf
Product Rule
• Type A
• Rh(-)
• PGM-2
39%
15%
6%
(.39) * (.15) * (.06) = .00351
1/.00351 = 284.9
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Sperm
• Among the smallest and most
highly specialized cells in the
human body.
• Has a head and a tail
• Contains 23 chromosomes
with the genetic material
found in the head
• Males release 2.5 to 6
milliliters of seminal fluid per
ejaculation with approximately
100 million sperm per milliliter.
Magnified 400X
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Semen
Determination of Seminal Fluid
• Acid phosphatase color test
– acid phosphatase will turn purple in the
presence of sodium alpha
naphthylphosphate and Fast Blue B.
– will fluoresce under UV light when it comes
in contact with 4-methyl umbelliferyl
phosphate.
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Acid phosphatase color test
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Semen
Determination of Seminal Fluid
• Prostate Specific Antigen
(PSA) or p30--unique to
seminal plasma
– P30 is isolated and injected
into a rabbit where antibodies
are produced (anti-p30)
– The formation of a precipitation
line shows the presence of p30
in the sample stain. It must be
seminal fluid.
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Secretors
• 80% of people are considered secretors.
Their blood-type antigens are found in high
concentration in their body fluids such as
saliva, semen,vaginal secretions and gastric
juice. If you are a secretor, you will have a
higher concentration of A and B antigens
than does your blood!!
• With the advent of DNA, the secretor
evidence is not as important as it once was.
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