The Nature of Blood
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
1980s, forensic serology was a most important part of lab
procedures. With the development of DNA techniques, more
time, money, and significance were placed on 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 Characteristics
Plasma is the fluid portion of the blood (55
percent).
Cells (45 percent)
Erythrocytes are red blood cells. They
are responsible for oxygen
distribution.
Leukocytes are the white blood cells;
they are responsible for “cleaning”
the system of foreign invaders.
Thrombocytes or platelets are
responsible for blood clotting.
Serum is the liquid that separates from the
blood when a clot is formed.
Historical Perspective of Blood Typing
Around 1900, Karl Landsteiner discovered that there are four
different types of human blood based on the presence or
absence of specific antigens found on the surface of the red
blood cells.
In 1940, Landsteiner and Weiner reported the discovery of the Rh
factor by studying the blood of the Rhesus monkey. 85 percent
of Caucasians, 94 percent of Black Americans, and 99 percent
of all Asians are Rh positive.
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
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.
Blood Terminology
ABO blood groups—based on having A, B, both, or 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
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
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
Blood Typing
Blood type A has antigen A on the surface of the cell and will
agglutinate with blood type B.
Blood type B has antigen B on the surface of the cell and will
agglutinate with blood type A.
Blood type AB has antigens A and B on the surface of the cells and
will not agglutinate with either type A or type B blood.
Blood type O has neither antigen A nor B and will not agglutinate.
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-
How common is your blood type?
46.1%
38.8%
11.1%
3.9%
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
Blood Groups
Type
Antigen
Antibody
Can Give Can Get
Blood To 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
Blood Evidence
Class evidence for blood includes blood type. If you can determine
the DNA, you will have individual evidence.
Bloodstain patterns are considered circumstantial evidence in a
courtroom. Experts can argue many points, including direction of
travel, height of the perpetrator, position of the victim, left/right
hand, whether the body was moved, etc.
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.
Microscopic
Views
Fish Blood
Bird Blood
Horse Blood
Frog Blood
Cat Blood
Dog Blood
Human Blood
Snake Blood