Serology; the study of
bodily fluids
• Living portion of blood is:
• Erythrocytes (red blood
cells…RBCs)
• Leukocytes (white blood cells)
• Platelets
Liquid part of the blood with no
cells in it is called the plasma.
(Mostly water with salts, ions,
proteins.)
Separation of blood
BLOOD TRANSFUSIONS were not working!
OUTLAWED IN MOST COUNTRIES IN EARLY 1900’S
ABO Blood Typing
(Karl Landsteiner – 1901)
A classification of blood: A, B, AB, O
Rhesus monkey factor (Rh) discovered in 1940.
If you have it, you’re Rh+ and if you don’t you’re Rh-
Theoretically, no two people have the same combination of blood factors and it
should be possible to individualize evidence using blood, but in reality this is
not the case.
Testing for every factor on RBCs in not practical, and many factors break
down as blood dries and ages.
Blood is still important in forensics because testing can be done on both whole
blood and dried bloodstains quickly and inexpensively.
Each antibody binds to a
specific antigen; an
interaction similar to a
lock and key.
The antibody destroys
the antigen
AGGLUTINATION
THE CLUMPING
TOGETHER
OF RED BLOOD
CELLS
Lattes slide method
Uses
antibody-antigen
reactions
to test for
blood types
Blood typing can be used to:
-show that two samples had different origins (exclude a suspect)
-determine the probability of an individual having a particular
blood type
What is the probability that an
American has type AB- blood?
4/100 x 15/100 = 60/10,000 or 0.6%
Determines whether a substance is blood or not, but does
NOT distinguish between human and animal blood.
Hemastix test
LUMINOL TEST
LUMINESCES WITH BLOOD OR SEMEN
PRECIPITIN
TEST
• Determines if
blood is human
• An animal
(mammal) is
injected with
sample. If
human, animals
produce
antibodies.
Non-mammals
Oval red blood
cells with a
visible nucleus
Mammals
• Circular redblood cells
• No nucleus
Secretors
• 80 % of population
• Blood type antigens
are secreted in bodily
fluids (saliva, semen,
perspiration,
gastric and vaginal
secretions)
Blood
enzymes
Proteins that regulate
chemical reactions
Iso-enzymes
Protein components into which enzymes can be separated
(1) PGM – an enzyme that has 10 variations
(2) importance- allows forensic scientists
to reduce the number of possible sources
BLOOD SPATTER
SIZE AND SHAPE OF DROPS
ARE AFFECTED BY:
• HEIGHT OF FALL
• ANGLE OF IMPACT
• SURFACE ON WHICH THE DROPS LAND
Shape is
determined by
the impact
angle
Measure the length
and width
of the stain
Determination of Impact Angle
• Divide the width by the length to get arc sine of the impact angle
Width / Length = arc sine of impact angle
Ex:
width = 2.4 cm
length = 3.1 cm
Ratio of width/length =
2.4 cm / 3.1 cm =
.77419
50.7
Enter:
“sin -1 (.77419)”
Answer:
50.7 degrees
Use your calculator to get the
impact angle
1. Height of drops vs. drop
size
2. Angle of drop vs.
drop shape
3. Surface texture vs. drop
size and shape
Blood spatter labs
The Nobel Prize in Physiology
or Medicine – Educational
(Blood type simulation)
American Justice; Jeffrey MacDonald