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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?
http://learn.genetics.utah.edu/units/basics/blood/types.cfm
There are 3 alleles or genes for blood type: A, B, & O. Since we have 2 genes, there are 6 possible combinations.
Blood Types
AA or AO = Type ABB or BO = Type B
OO = Type OAB = Type AB
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-).
A+ A-B+ B-
AB+ AB-O+ O-
http://www.fi.edu/biosci/blood/rh.html
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?
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 Donor
Universal Recipient
Blood Groups
Type Antigen Antibody Can GiveBlood To
Can GetBlood From
A
B
AB
O
A
B
A and B
NeitherA nor B
B
A
NeitherA nor B
A and B
A, AB O, A
B, AB O, B
AB
A, B, O, AB
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
Bird Blood
Cat Blood
Dog Blood
Fish Blood
Frog Blood
Snake BloodHuman Blood
Horse Blood
