1. Johnston Sr. High Forensics Mrs. Florio
Forensic Serology
Johnston Sr. High
Forensics
Mrs. Florio

2. Learning Objectives
1) List the A-B-O antigens and antibodies found in the blood for each of the 4 different blood types – A, B, AB, O
2) Understand and describe how whole blood is typed
3) List and describe forensic tests used to characterize a stain as blood

3. Learning Objectives (continued)
4) Understand the concept of antigen/antibody interactions and how it is applied to species identification and drug identification
5) Understand the inheritance of blood types

4. History
Karl Landsteiner – figured out blood was categorized – won Noble Prize
All human blood is not the same
Blood transfusions were previously a failure before this time
Developed ABO system
How may blood help at a crime scene?

5. The Nature of Blood
Mixture of cells, enzymes, proteins, and inorganic substances
Fluid portion – plasma
Mostly water, 55% of blood content
Suspended in plasma – cells (45%)
Red blood cells (erythrocytes)
White blood cells (leukocytes)
Platelets
Yellow portion in pic is serum (shown when
Clotting factor in blood is removed, centrifuged)

6. Antigens
Role of RBCs?
Transport oxygen to body tissues and remove carbon dioxide from tissues
On surface of all RBCs there are millions of chemical structures called ANTIGENS
a substance, usually a protein, that stimulates the body to produce antibodies against it

7. How does this relate to blood type?
Blood Type A – each RBC has A antigens on surface
Blood Type B – RBCs have B antigens
Blood Type AB – RBCs have both A and B antigens
Blood Type O – RBCs don’t have either A or B antigen

8. What about the Rh factor? + or -?
Rh factor – another antigen, sometimes called the D antigen
If you have it on RBCs = +
If you lack it = -
In blood banks, they must look for the presence of A, B, and Rh factor before donating blood

9. Antibodies Serum contains proteins called antibodies
Protein in the serum that destroys or inactivates a specific antigen
Anti-A – specific for only A antigen
Anti-B - for only B antigen
Anti-D – for only D antigen
Antiserum – blood serum containing specific antibodies

10. Antigen-Antibody relationship
Antibody reacts only with its specific antigen
Serum with anti-B added to RBC carrying B antigen, two will combine, causing antibody to attach itself to cell
Antibodies are bivalent – have 2 reactive sites, can attach to 2 RBCs

13. Agglutination
Antibody’s ability to be bivalent creates vast network of cross-linked cells seen as clumping, or agglutination.
Normal blood (L) antigens & antibodies coexist b/c antibodies present are not specific towards any of antigens
A foreign serum was added to blood (R) and causes antigen/antibody reaction, causing RBCs to link (agglutinate)

14. Blood Groups

15. Blood Typing Serology – study of antigen-antibody reactions
Ex: ABO identity
Type A type is agglutinated by anti-A serum (not natural)
Type B aggl. by anti-B
Type AB aggl. by both anti-A and anti-B
Type O aggli. by neither antibody sera

16. Population Distribution of Blood Type
AB – 3%

17. Population Frequencies

18. Cool Website on Blood Typing
Blood Typing Game

20. Level 6 Article Quiz Name one example of a test to detect blood.
What are the four different blood types?
What are the three main antigens? Where are they found specifically?
What do antibodies do to antigens?
Name 3 components to blood.

21. Level 6 continued… 6) What term describes the way blood flows slowly?
a) water y b) viscosity c) spatter
7)Which blood type has the highest frequency? (most common, neglecting Rh)
8) A person with blood type B has ____ antigens and ___ antibodies.

22. Level 6 continued…
9) Blood that flies off a surface under pressure is a(n) __________ stain.
a) projected b) transfer c) colloid
10) WBCs make up ___ percent of total blood volume.
a) 50% b) 10% c) 5%
11) This is the name for a test used to determine if blood is animal or human.

23. Level 7 Quiz
Which scientist was responsible for organizing blood into types?
If you have blood type O, with blood types can you receive?
Name the 4 main blood types.
What are the three “solid” parts in the blood?

24. Level 7 continued… 5) Be specific…where are antigens found?
6) Someone with blood type AB has ______ antigens and ____ antibodies.
7) What is the most common blood type? (neglecting Rh)
8) Term describing the ability of antibodies to attach to 2 antigen site.

25. Forensic Characterization of Bloodstains
Questions the criminalist must ask regarding blood stains…
1) Is it blood?
2) From what species does the blood originate?
3) If blood is human, how closely can it be associated with a particular individual?

26. Types of Tests Presumptive Confirmatory
Is It Blood, Semen, Urine, Saliva?
Look for proteins, substance activity
Confirmatory
Confirms the presence of the bodily fluid

27. COLOR TESTS – Presumptive test for Blood
Kastle-Meyer Test
Based on the fact that blood hemoglobin possesses peroxidase-like activity
Hemoglobin: RBC protein that transports oxygen
Peroxidases: enzymes that accelerate the oxidation of many organic compound when combined with peroxides
Combination of blood, peroxide, & phenolthalein reagant produces pink color

28. More on Kastle-Meyer Why is it not confirmatory?
False positives – oxidizing metals, potatoes, horseradish

29. Luminol – Another Presumptive Test for Blood
Reaction of luminol with blood produces light, rather than color
Must darken room – will produce a faint, blue glow – luminescence
Extremely sensitive, capable of detecting bloodstains diluted up to 300,000 times

30. Luminol – What you see

31. Takayama – Confirmatory for blood
Tests for human hemoglobin
Small amount of blood added to microscope slide
Chemical solution is added and heated
Crystals viewed under microscope
Also uses microscopy to detect blood cells

33. Precipitin Test Human or animal origin?
Precipitin – antibody that reacts with its corresponding antigen to form a precipitate
when animals are injected with human blood, antibodies form that react with the invading human blood to neutralize its presence

34. Gel Diffusion
Antibodies and antigens will diffuse or move toward one another on a plate made with a gel medium (agar).
Can also do this under influence of electrical field (electrophoresis)