Transcript Forensics Blood

Blood
Blood Evidence
Blood typing = class evidence
 DNA profiling = individual evidence
 Blood-spatter: recreate crime scene

History of the study of blood
2500 B.C.
Egyptians - bloodletting to cure
diseases
500 B.C.
Greeks – distinguished between
arteries and veins
1659 A.D.
Leeuwenhoek – view blood cells with
microscope
1795
First blood transfusion performed
1901
Landsteiner – discovered 3 blood types
(A, B, O)
1902
Decastello – discovered AB blood type
1922
Oliver – established blood donor
service
1935
Mayo Clinic – developed a method to
store blood for transfusions
1900s
Kastle – developed first presumptive
blood test
1959
Belgian Congo – first AIDS case
recorded
1984
Gallo – identified virus causing AIDS
1987-2002 Development of blood-screening tests
for infectious disease
Composition of Blood
1.
Cells (45%)
 red blood cells (RBC)
 white blood cells (WBC)
 Platelets
2.
Plasma (55%)
 90% water
 Dissolved proteins (antibodies, hormones,
clotting factors)
 Nutrients (O2, glucose, amino acids, salts,
minerals)
 Wastes (urea, CO2)
Red Blood Cells
Erythrocytes
 carry gases (oxygen, carbon dioxide)
 produced in bone marrow
 no internal organelles (no nucleus)
 hemoglobin is iron-containing protein that
binds to O2

– gives blood the red color
White Blood Cells
Leukocytes
 fights disease and foreign invaders
 produced in bone marrow
 true cell – has nucleus

Platelets
Tiny cell fragments
 Helps in blood clotting

Kastle-Meyer
Presumptive Blood Test
Procedures
Wet cotton swab with distilled water and gently
rub on stain
 Ethyl alcohol: breaks open cells, exposes
hemoglobin
 Phenolphthalein (Kastle-Meyer Reagent):
reducing agent; turns pink when oxidized
 Hydrogen peroxide: reacts with hemoglobin

If blood is present, swab will turn PINK.
False Positives

Some non-blood substances can yield a
positive Kastle-Meyer test:
– vegetables with peroxidases (potatoes, beets,
horseradish, broccoli, cauliflower)
– copper and nickel salts
Leucomalachite Green

Leucomalachite Green, or LMG
– Similar to Kastle-Meyer test
– Replaces phenolphthalein with leucomalachite
green
– When added to the substance, a green color
will be produced will be produced if blood is
present.
Blood Typing
Why do blood typing?
Less expensive and quicker than DNA
profiling
 Class evidence
 Can be used to link or exclude suspect to
crime scene (but doesn’t prove guilt)

Discovery of Blood Types
Karl Landsteiner (1901)
 Blood from one person did not always mix
freely with another person
 Clumping of mixed blood results in death
 Cell-Surface Proteins (RBC’s):

– A and B proteins
– Rh factor proteins

Antibody reaction test used to identify
blood types
ABO Blood Types
42%
Type
 Type
 Type
 Type

12%
3%
43%
A: has A antigen on surface of RBC
B: has B antigen
AB: has both A & B antigens
O: has no antigens on surface
Antibodies
Our bodies have the ability to recognize
between own cells (self) and foreign
invaders (non-self)
 White blood cells engulf and digest
invaders
 Antibodies: Y-shaped proteins secreted by
WBC’s which aid in immune response
 Antibodies bind to antigens (foreign
substance or cell that reacts to antibodies)

Antibodies
 Type A: makes anti-B antibodies
 Type B: makes anti-A antibodies
 Type AB: no antibodies
 Type O: makes anti-A and anti-B
antibodies
Antigen-Antibody Response
Immune system attacks and
destroys foreign invaders:
WBC’s make antibodies that
attach to foreign proteins
2. WBC’s engulf invader
1.
Agglutination: clumping of blood
cells
Rh Factor

Rh protein found on RBC’s when
Alexander Weiner worked with Rhesus
monkeys (1940)
Rh+ : 85%
Rh- : 15%
Blood Typing Analysis
Blood Typing Analysis
Blood sample mixed with 3 antibodies
 If blood clumps, proteins are present
 If no clumps, no proteins are present

Anti-A antibody test
Anti-B antibody test
Rh antibody
test
Other forms of identification
Additional enzymes and proteins have been
found in the blood:
– Phosphoglucomutase (PGM)
– Adenylate kinase (AK)
– Adenosine deaminase (ADA)
– Esterase D (EsD)
– Glucose-6-phosphate dehydrogenase (G-6PD)
– Polymorphic proteins: Group-specific
Components (Gc) and haptoglobins (Hp)