1. WARM-UP Do you know your blood type? Have you ever donated blood?
Have you ever received a blood transfusion or know someone who has?
What do you think is the importance of blood typing in Forensic Science?
What are you looking forward to in this unit, what are you dreading?

2. Identification Using Blood Groups
Forensic Serology
Identification Using Blood Groups

3. Forensic Serology
Serology – term used to describe a broad range of laboratory tests using reactions of blood serum and body fluid
The serology section of a forensic laboratory may deal with any or all of the following:
blood typing
characterization of unknown blood
stain patterns for crime reconstruction
paternity testing
semen or saliva identification
DNA techniques used for identification

4. Forensic Characterization of Bloodstains
Three questions that must be answered by the forensic investigator:
1) Is it blood?
Benzidine Test
Kastle-Meyer Test
Hemastix (o-tolidine, TMB)
Luminol Test
2) Is it human blood?
Precipitin Test
3) Can it be associated with an individual?
Blood Type Testing (anti-serums)

5. Blood Antigens
On the surface of red blood cells are chemical structures (proteins) called antigens
The presence of antigens allow a living system to recognize foreign biological substances
Antigens also impart specific characteristics to the red blood cells. These characteristics can be partly used to identify individuals
Human red blood cells have more than 15 different antigen types that have been discovered

6. Blood Typing
Blood typing involves determination of the antigens present on an individual’s red blood cells (RBCs)
The two most common blood typing systems used are the A-B-O method and the Rh method
type A blood – contain “A” antigen on RBCs
type B blood – contain “B” antigen on RBCs
type AB blood – contains both A and B antigens
type O blood – contain no A or B antigens
Rh+ blood – contain Rh antigen
Rh- blood – no Rh antigen

8. Blood Typing
Blood also contains antibodies – proteins that recognize and bind to certain, specific antigens
Blood Type Antigens on RBC Antibodies
A A anti-B
B B anti-A
AB AB none
O none both A & B
Rh Factor: A red blood cell that contains Rh antigens is said to be positive; no Rh antigens is said to be negative. The antibody is called “anti-D”

10. Blood Typing
Red blood cells containing A antigens do not combine with B antibodies
Red blood cells containing B antigens are clumped together (blood clot) in the presence of B antibodies

11. Blood Typing
Human serum containing specific antibodies can be purchased
Separately mix a drop of unknown blood sample with drop of each anti-serum
Reaction between blood and anti-serum
No reaction between blood and anti-serum

12. Blood Typing Example
A sample of unknown blood is mixed with three anti-sera samples:
Tube 1 (Anti-A): No reaction
Tube 2 (Anti B): No reaction
Tube 3 (Anti Rh): Cloudy reaction
In terms of the A-B-O and Rh systems, what type blood is the sample?
The ABO antigens are not confined to RBC; 80% of Americans are secretors, same antigens found on other cells
O positive

14. Principles of Heredity – Vocabulary Review
Gene: basic unit of heredity, consisting of a DNA segment located on a chromosome.
Chromosome: a threadlike structure in the cell nucleus, along which the genes are located.
Egg: female reproductive cell
Sperm: male reproductive cell
Zygote: cell arising from the union of an egg and a sperm cell
X-chromosome: female sex chromosome (XX – female)
Y-chromosome: male sex chromosome (XY – male)

15. Principles of Heredity – Vocabulary Review
Allele: any form of a gene located at the same point on a particular pair of chromosomes
Homozygous: a gene pair made up of two similar alleles (dominant/dominant AA & BB; recessive/recessive OO)
Heterozygous: a gene pair made up of two different alleles (dominant/recessive AO & BO; co-dominant AB)
Genotype: pair of allele genes in cell
Phenotype: physical manifestation of a genetic trait (shape, color, blood type)
Ex. Phenotype: Type A Genotype possibilities: AA or AO

17. Punnett Square Practice
If a mother has type AB blood, and a father has type O blood, answer the following questions:
What is the genotype of the mother and father?
What are all the possible genotype combinations their offspring could have? Fill out the Punnett square below.
A B O
- 50% Chance offspring is Type A
- 50% chance offspring is Type B AO BO

18. Paternity Testing in Forensics
Genotyping of blood factors useful applications for transmissions of blood characteristics, but no direct relevance to criminal investigations
Has implications in disputed-paternity cases (civil, not criminal cases)
Resolved by comparing blood group genotypes of suspected parents and offspring. Does not always mean the suspect is the father, as many other males may also have the same blood type
HLA (human leukocyte antigen) test looks at white blood cell antigens (90% accurate)
DNA test procedures (over 99% accurate)

19. Punnett Square Practice
Jane has type AB blood, and John has type O blood. If Jane’s child has type AB blood, is there a possibility that John is the father?
A B O
In the words of Maury Povich:
“John… You are NOT the father” AO BO AO BO