1) Forensic serology involves analyzing blood, semen, saliva and other bodily fluids to answer key questions in criminal investigations. 2) Blood typing examines the antigens on red blood cells to determine a person's blood group using the ABO and Rh systems. Mixing blood samples with specific antibodies can indicate blood type. 3) Analysis of bloodstain patterns and dimensions can provide clues about the direction and angle of impact to reconstruct crime scenes.

1. Forensic Serology
Identification Using Blood Groups
This presentation contains graphic pictures.

2. 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 identification in rape cases
• DNA techniques used for identification

3. The Composition of Blood
Blood is a mixture of many components:
cells inorganic substances (salts)
enzymes water
proteins
55 % of blood content is plasma – mostly water
and substances dissolved in it
Most of the solid materials (by weight) are cells
red blood cells, RBCs (erythrocytes)
white blood cells (leukocytes)

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?

5. Luminol
• Red blood cells contain hemoglobin
(Hb) – the protein responsible for
transporting oxygen
• Each Hb contains four iron (Fe)
containing hemes
Heme structure

6. Luminol
• Red blood cells contain hemoglobin
(Hb) – the protein responsible for
transporting oxygen
• Each Hb contains four iron (Fe)
containing hemes
Heme structure

7. Forensic Characterization of Bloodstains
Three questions that must be answers by forensic
investigator:
1) Is it blood?
Benzidine Test
Kastle-Meyer Test
Hemastix (o-tolidine, TMB)
Luminol Test
Enzymatic Tests
2) Is it human blood?
Precipitin Test
3) Can it be associated with an individual?

8. Precipitin Test

9. 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

10. Blood Typing
Blood typing involves determination of the antigens
present on an individual’s 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

11. 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

12. Blood Typing
When blood containing a
specific antigen is mixed with
blood containing the
corresponding antibodies, the
blood clots
The clots can then be
removed by the host system

13. 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

14. 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, found on other cells

15. 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

16. Blood Splatter Analysis
Categories of Bloodstains:
Passive (dripping)
Transfer (smearing)
Projected
Projected Bloodstains occur in shootings, trauma
from blunt weapons, hacking, or slashing attacks.

17. Projected Bloodstain Analysis
Two Important Determinations:
a. direction of splatter
b. angle of impact with surface
sin α = (width drop / length drop)

18. Forensic Characterization of Semen
Many crimes involve sexual misconduct
Normal males, upon ejaculation, release seminal fluid. This fluid
is a mixture of components:
• water
• spermatozoa
• enzymes
• inorganic salts
Semen at a crime scene (clothing, bed sheets, carpet, cushions)
can be located and identified by three common methods:
• microscope examination to find sperm
• acid phosphatase test
• p30 (also called prostrate specific antigen) immunoassay test

19. Forensic Characterization of Saliva
Saliva is a mixture of many components:
99% water
Mucin (protein helps in swallowing)
Amylase (enzyme to help digest carbohydrates)
Cheek cells (good for DNA)
Adults produce 1.0-1.5 liters of saliva/day and it is not
uncommon at crime scenes (especially involving bite marks).
A simple test for saliva involves mixing
starch, iodine, and a sample of the
presumed saliva together. Starch and
iodine are a deep blue color when mixed
together. The amylase breaks down
starch, however, and the color fades
(takes about 15 mins @ 37 o
C).