Forensics Unit 4 Notes
Chapter 11 – Blood
Serology- the study of bodily fluids
I.
Blood – class evidence
a. Can be individualized if conditions are right – DNA
b. Plasma- the fluid portion of blood, obtained by centrifuging a sample of whole blood
c. Solid portion of blood
i. Erythrocytes-red blood cells
ii. Leukocytes-white blood cells
1. Has antibodies- respond to antigens and produce an immune response
2. Unique to people who are exposed to a foreign substance
a. disease
b. snake bite
c. bacteria
d. someone else’s blood
3. Valuable for DNA extraction
iii. Platelets – begin the clotting process
d. Blood Factors-specific combination of antigens, enzymes and proteins in blood
i. Many break down as blood dries
ii. No 2 people (besides identical twins) have the exact same blood factors
iii. Rh Factor-a basic blood factor besides ABO (+ or - , positive or negative)
e. Secretors- 80% of the population has blood antigens in bodily fluids besides blood
II.
How do you know if the stain is blood?
a. Presence of Heme in hemoglobin- the oxygen carrier that gives red blood cells their color.
i. Breaks down peroxides with the production of oxygen
ii. Used for the Hematest tablets or strips – turn blue
b. Luminol – (the one you see on T.V.) presumptive test for blood - chemiluminesce- emission of
light from a chemical reaction,
III.
How do we put blood into different classes?
a. Human or Animal?
i. Precipitin test- test that distinguishes b/t human and animal blood
1. uses an animal serum – a liquid that separates from clotted blood
2. Serum has antibodies specific to human antigens.
3. Antigens-foreign substances in the body that are capable of causing disease,
antigens trigger an immune response
4. agglutinate- red blood cells clump together in response to a particular antibody
b. ABO classification system- based on reaction of antigens and antibodies
Blood Type
A
B
AB
O
IV.
Antigen
A
B
A&B
none
Donor Blood Factors
Antibody
Donor for
B
A, AB
A
B, AB
None
AB
A&B
All
What can we learn from blood patterns?
a. LINK
Recipient for
A, O
B, O
All
O