1. Forensic Serology

2. Karl Landsteiner
First person to recognize that all human blood is not the same
Blood is distinguishable by its’ group or type
Now called the A-B-O System
Important because using the wrong blood cause instant death for those receiving transfusions
Today there are more than 100 different blood factors known

3. Blood as Identification
In theory, no two individuals, except for identical twins, could have the same combination of all individual blood factors (not just blood types)
Blood factors are controlled genetically and have the potential of being a distinctive feature for personal identification
Important in serious crimes where blood is found at a crime scene—homicides, assaults, and rape.

4. Blood as Evidence
Blood typing not so useful anymore because of DNA technology
Scientists can now characterize biological evidence by selecting regions of our DNA

5. The Nature of Blood
Blood: complex mixture of cells, enzymes, proteins, and inorganic substances
Plasma: the fluid portion of blood
Mostly water
55% of blood content
The other 45% is made of solid particles

6. The Nature of Blood Erythrocytes: red blood cells; found in plasma
Leukocytes: white blood cells; found in plasma
Platelets: clotting factor; found in plasma
Serum: the liquid that separates from the blood when a clot is formed

7. Important Parts for Forensic Science
Red Blood Cells—because of their importance in blood typing
Serum—because of its’ importance in carrying antibodies

8. Red Blood Cells and Blood Types
Protein resides on the Red Blood Cell called antigens
Antigens give blood-type characteristics to the Red Blood Cells
ABO and Rh systems are the most important blood types

9. Antigens and Blood Types
Type A Blood has Antigen A on the surface of the Red Blood Cell
Type B Blood has Antigen B on the surface of the Red Blood Cell
Type AB Blood has both Antigen A and Antigen B on the surface of the Red Blood Cell
Type O Blood has neither Antigen A nor Antigen B on the surface of the Red Blood Cell

10. Distribution of Blood Types in US
Type O Blood is the most prevalent with 43%
Type A Blood is the next most common with 42%
Type B Blood is less common with 12%
Type AB Blood is the most rare type with 3%

11. Rh Factor or D Antigen
Blood that contains the D Antigen is referred to as Rh +
Blood that does not contain the D Antigen is referred to as Rh -

12. A, B, D—that determines a person’s blood type.
In routine blood typing, it is the presence or absence of the three antigens—
A, B, D—that determines a person’s blood type.

13. Fundamental Principle of Blood Typing
Serum contains proteins known as antibodies
For every antigen, there is a specific antibody that reacts against it.
Anti-A reacts against antigen B
Anti-B reacts against antigen A
When antibodies react against its’ specific antigen, agglutination or clumping of RBCs occur.

14. Blood Type Antigens on RBCs Antibodies in Serum
Antigen A
Anti-B B
Antigen B
Anti-A AB
Antigen A and Antigen B
Neither Anti-A nor Anti-B O
Neither Antigen A nor Antigen B
Both Anti-A and Anti-B

15. What is Serology?
The term serology refers to a broad scope of laboratory tests that use specific antigen and serum antibody reactions.
Blood typing falls into this category.

16. Forensic Characterization of Blood Stains
Important Questions:
Is it blood?
From what species did the blood originate?
If the blood is human, how closely can it be associated with a particular individual?

17. Preliminary Determination of Blood
Sample tested with phenolphthalein
Turns deep pink color Positive for blood
Also known as the Kastle-Meyer Test
Use of Hemastix
When moistened with distilled water and placed in contact with stain, a bright green color indicates blood.

18. Preliminary Determination of Blood
Luminol Test
Produces light if blood is present in a darkened area
Extremely sensitive: can detect stains diluted up to 300X
Will not interfere with any subsequent DNA testing

19. Is it human blood? Precipitin Test:
Human blood is inserted into animal (rabbit)
Rabbits produce antibodies to react against the human blood
Blood is drawn from rabbit that contains the human antibodiesproduces human antiserum
Unknown blood sample, if human, will react with the human antiserum from the rabbit by forming a precipitate

20. Is it human blood? Gel Diffusion and Electrophoresis
Antibodies and antigens will move toward each other on an agar gel plate or in an electrophoresis chamber
Forms a precipitate where the human antibodies and antigens meet
No precipitate? Unknown sample is not human blood

21. Effectiveness of Tests for Human Blood
Precipitin Test:
Very sensitive and requires only a very small amount of blood
Works on very old samples
Even in washed items blood may be detected