1. The study of body fluids
Serology
The study of body fluids

2. Serology-Definition The study of antigen/antibody reaction
The study of biological fluids
Blood, sweat, tears, saliva, semen, etc.

3. But, I was not even at the crime scene…
If you leave behind a body fluid sample, it proves your presence at the scene.
Serological evidence has more weight than fingerprinting.
Often used in cases of paternity and ancestry

4. Quiz… What is the most common body fluid left behind at a crime scene?
Blood

5. Blood Info Plasma Leukocytes – white blood cells
Liquid portion of whole blood
Contains proteins, enzymes, clotting factors, electrolytes, and 3 types of cells
Leukocytes – white blood cells
Erythrocytes – red blood cells
Platelets – cells involved in clotting

6. Blood Serum
When blood clots and the clotted material is removed, a yellowish liquid remains
Yellowish fluid is serum
Serum contains the majority of proteins and enzymes
Serum contains the antibodies

7. Important components
2 components of blood are very important to forensic scientists
RBC’s and serum
With these two components, a serologist can determine blood type from any sample or stain
With more than 100 blood factors known, it is theoretically impossible for two people other than identical twins to have the same combination of blood factors.

8. Blood Types
Dr. Karl Landsteiner – responsible for ABO blood typing system, allowed for safe matching of blood donor to recipient
Knowing the blood type helps to narrow the suspect list

9. Blood Types Determined by antigens present on cells A – a antigen
B – b antigen
D antigen – Rh factor
Found in most people, responsible for violent antigenic reactions
Can be harmful if Rh negative meets Rh positive during mating

12. Antigens
A substance, usually a protein, that stimulates the body to produce antibodies to fight an intrusion
There are more than 15 known blood antigens

14. Antibody For every antigen, there is an antibody
An antibody is highly specific, this means that only recognizes and interacts with its specific antigen
The combination of antigen and antibody forms an antigen-antibody complex – the basis for blood typing

15. How do you type blood?
Use antiserum to test for agglutination (clumping)
Anti A – will make type A clump
Anti B – will make type B clump
Type O will not clump with either Anti A or Anti B
Anti Rh – will make Rh+ clump

16. Some Blood Statistics 43% of Americans have type O
42% of Americans have type A
12% of Americans have type B
3% of Americans have type AB

17. Who is the Universal Donor?
A- receive blood from A & O
Give to A & AB
B- receive blood from B & O
Give to B & AB
AB- receive blood from A, B, AB, O
Give to AB
AB is the Universal Receiver
O- receive blood from O
Gives to A, B, AB, and O
O is the Universal Donor

18. What to do with crime scene blood…
Type each blood sample separately
At scenes with multiple victims, typing and antigen-antibody complexes help reconstruct crime scene

19. How much blood is needed?
Modern technology allows us to test minute amounts of blood, but the sample does not hold substantial weight like a large sample
Chemical reactions from the antigens and DNA fingerprinting could degrade small samples
Putrefaction- the decay of cells due to bacterial activity in old samples

20. What is done with blood evidence?
Typing often tells the story of how and when things happened
Time of bloodstain is difficult to determine
Exclude suspects
Extract DNA
Pg in text for explanation of why time is hard to determine

21. Secretors
A secretor is a person who provide blood typing requirements in all body fluids.
Examples: saliva, semen, gastric juices, etc.
Do not confuse blood typing with DNA typing – you can obtain DNA from all body fluids of every person
DNA TYPING AND BLOOD TYPING ARE NOT THE SAME THING

22. How do you know if a stain is blood?
Presumptive Testing
Kastle-Meyer Color Test
Hemastix
Luminol
Specific Testing
Microcrystalline Test
Precipitin Test

23. Kastle-Meyer Color Test
Blood stain + phenolphthalein + hydrogen peroxide = deep pink color
Being a color test, it is only considered presumptive
False Positives: Potatoes and Horseradish

24. Hemastix Test
Hemastix strip moistened with distilled water + blood sample = green color
Also a color test and thus is presumptive

25. Luminol Test Luminol + blood + dark = light Must be viewed in the dark
Extremely sensitive
Can detect bloodstains diluted up to 10,000,000 times
Does not interfere with DNA testing

26. Microcrystalline Test
Confirmative test
2 popular versions
Takayama
Teichmann
Both versions depend on chemical additions to the blood
Test is susceptible to interferences of contamination

27. Precipitin Test Human antiserum added to blood sample
If agglutination occurs, then the sample is human blood
2 methods: capillary tube, gel diffusion
Can be used on samples up to yrs old
Has produced positive test on 4-5 thousand year old mummies

28. Not human blood?
You can still use the precipitin test with other antiserums
Using a species specific antiserum, a serologist can determine the source of the blood

29. DNA Fingerprinting/Typing
Testing for paternity
You inherit your blood type from your parents
Paternity confirmation plays a role in child support, custody, visitation
Also has role in crimes that involve kidnapping, insurance fraud, and inheritance

30. Heredity Transmission of hereditary material is done through genes
Genes are found on chromosomes
Humans have 46, 23 from mother, 23 from father, found in pairs resulting in 23 chromosomes in normal cells
XX – female
XY – male
Females always donate X, Males donate either X or Y

31. Genetics Locus- Position of a gene on a chromosome
Alleles- alternative forms of genes
Homozygous- AA, aa
Heterozygous- Aa
Dominant- always represented
Recessive- not seen if dominant is present
Codominant- not seen in full effect

32. Genetics continued… Genotype- specific genetic make-up
Phenotype- observed characteristics
Punnet Square- diagram of genetic possibilities