Transcript Forensic Serology

Chapter 8 Forensic Serology
Courtesy of C. Fanning
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-1
Unit Objectives for Serology





Understand the anatomy and philology of blood.
Understand the concept of the antigen – antibody
interactions and how they are applied to species
identification and drug identification.
Contrast chromosomes and genes including
Punnett squares, genotypes and phenotypes of
offspring.
List and understand how whole blood is typed.
List and describe forensic tests used to characterize
a stain as blood.
Describe the proper collection of physical evidence
in a rape case.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-2
Nature of Blood
•The word blood refers to a highly complex mixture of cells,
enzymes, proteins, and inorganic substances.
•Plasma, which is the fluid portion of blood, is composed
principally of water.
•Red blood cells (erythrocytes), white blood cells (leukocytes),
and platelets are the solid materials suspended in plasma.
•Antigens, usually proteins, are located on the surface of red
blood cells and are responsible for blood-type characteristics.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-3
Nature of Blood
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-4
The
Circulatory
System


The main
arteries carry
blood to the
body.
Veins carry
blood back to
the heart.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-5
The Circulatory
System

Blood spirts out
from the arties
and veins
because of blood
pressure
provided by the
heart pumping
the fluid around.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-6
Blood Cells


Blood cells are formed in the bone marrow.
All blood cells arise from the same bone
marrow stem cells. Stem cells are immortal,
meaning they never die (at least not until
you do).
Stem cells are also undifferentiated.
meaning they have not yet developed into a
particular cell type. Furthermore, stem cells
are pluripotent, meaning they have the
potential to become any type of blood cell.
These immortal, undifferentiated, pluripotent
stem cells give rise to erythrocytes,
leukocytes and platelets.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-7
Leukocytes: Types and names


The diagram below illustrates the
different types of blood cells.
Leukocytes, also known as white blood
cells, are a group of related cell types
that involved in immune function.
Leukocytes include neutrophils,
eosinophils, basophils, lymphocytes
and monocytes.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-8
Leucocytes: White Blood Cells
and Erythrocytes : Red Cells
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-9
Erythrocytes: Red Cells


Erythrocytes, also known as red
blood cells (RBCs), function to transport
oxygen in the blood. The shape of
erythrocytes is ideal for this function, they
are biconcaved discs.
This shape increases the surface area-tovolume ratio of the cell, thus increasing the
efficiency of diffusion of oxygen and carbon
dioxide into and out of the cell. They have a
flexible plasma membrane. This feature
allows erythrocytes, which have a 7mm
diameter, to squeeze through capillaries as
small as 3 mm wide.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-10
Red Blood Cells – cont.

Erythrocytes contain tremendous amounts
of hemoglobin, the protein that binds
oxygen. In order to make room for more
hemoglobin to carry more oxygen,
erythrocytes loose their nucleus and other
organelles as they develop in the bone
marrow. Because they lack a nucleus and
other cellular machinery, erythrocytes
cannot repair themselves when damaged,
consequently they have a limited life span of
about 120 days.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-11
Erytropoesis:
Production of
Blood Cells

The removal of old and dying erythrocytes is
carried out by the spleen. Erythrocytes,
which represent the most numerous cell
type in the body die at a rapid rate, 2-3
million erythrocytes die every second.
Erythrocyte production must equal
erythrocyte death or the cell population
would decline. Erythrocytes are produced
through a process called erythropoesis.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-12
Hematocrit



Whole blood is composed of plasma
(liquid), cells and platelets. If whole
blood is placed into a tube and
centrifuged, the cells and the plasma
will separate.
The erythrocytes will pack into the
bottom of the tube, the plasma will be
at the top of the tube, and the
leukocytes and platelets will form a
thin layer in the middle.
The hematocrit is defined as the
percentage of whole blood made up of
erythrocytes.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-13
Hematocrits vary by Gender


This value is determined by dividing the
height of the erythrocytes by the total height
of the blood in the tube and multiplying by 100.
Hematocrits vary but there is a range of
values that is considered normal. Average
hematocrit values are:




males.......... 40-50%
females....... 38-45%
athletes........ > 50%
Any activity or condition that consistently lowers oxygen levels
in the blood will cause an increase in erythropoesis and a
subsequent rise in the hematocrit.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-14
How Blood Clots



Blood Clots on the outside of the body
to stop the flow of blood through cuts.
They can also form on the inside of the
body due to trama or disease.
http://www.biosbcc.net/doohan/sample/htm/Hemostasis.htm
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-15
Blood Clots
Blood clots have a 13
step process to form
blood clots.
Injuries like stabbings
and shootings can
cause secondary
blood clotting that can
kill the individual.
Lipid deposits can
cause thinning of the
blood vessels and
beginning points of
clots.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-16
Blood Clotting from injury
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-17
Blood Typing
•More than 15 blood antigen systems have been identified, but the
A-B-O and Rh systems are the most important. This system
determines which blood can be given to a patient and also helps to
identify and eliminate suspects in criminology.
•These blood types are due to antigens and antibodies that can
cause blood to clot or coagulate into small clumps.
•An individual that is type A has A antigens on his/her red blood cells,
type B has B antigens, AB has both A and B antigens, and type O
has neither A nor B antigens. The antibodies are in the blood and
determines which blood can be used in a transfusion attempt.
•Rh factor is determined by the presence of another antigen, the D
antigen.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-18
Blood Typing
•People having the D antigen are Rh positive; those not having the
antigen are Rh negative.
•For every antigen there is a specific antibody that will react with it to
form clumps known as agglutination.
•Thus, if serum containing anti-B is added to red blood cells carrying
B antigen, they will immediately react.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-19
Blood Agglutination Explained
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-20
Serology
•The term serology is used to describe a broad scope of
laboratory tests that use specific antigen and serum antibody
reactions.
•The identity of each of the four A-B-O blood groups can be
established by testing the blood with anti-A and anti-B sera.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-21
Serology Antigen-Antibody Reaction
•The concept of specific antigen–antibody reactions has
been applied to immunoassay techniques for the detection
of drugs of abuse in blood and urine.
When joined due to
incompatibilities
they form
agglutinations or
precipitates
Antigens and
Antibodies
freely flowing in
the blood.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-22
Immunoassay
•A number of immunological assay techniques are commercially
available for detecting drugs through antigen-antibody reaction.
•One such technique, the enzyme-multiplied immunoassay
technique (EMIT), is used by toxicologists because of its speed
and high sensitivity for detecting drugs in urine.
•In a typical EMIT analysis, antibodies that will bind to a specific
drug are added to the subject’s urine.
•Other immunoassay procedures are also available, such as
radioimmunoassay (RIA), which uses drugs labeled with
radioactive tags.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-23
Antigen-Antibody Reaction
•When an animal, such as a rabbit or mouse, is injected with an
antigen its body will produce a series of different antibodies, all
of which are designed to attack some particular site on the
antigen of interest.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-24
Antigen-Antibody Reaction
•This collection of antibodies is known as polyclonal antibodies.
•Alternately, a more uniform and specific collection of antibodies
designed to combine with a single antigen site can be
manufactured.
•Such antibodies are known as monoclonals.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-25
Forensics of Blood
•The criminalist must be prepared to answer the following
questions when examining dried blood:
1. Is it blood?
2. From what species did the blood originate?
3. If the blood is of human origin, how closely can it be
associated to a particular individual?
•The determination of blood is best made by means of a
preliminary color test.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-26
Testing for Blood
•A positive result from the Kastle-Meyer color test is highly indicative
of blood. Hemoglobin causes a deep pink color.
•Alternatively, the luminol test is used to search out trace amounts
of blood located at crime scenes.
•Luminol produces light (luminescence) in a darkened area.
Courtesy of C. Fanning
)
Courtesy of C. Fanning
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
Courtesy of C. Fanning
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-27
Testing for Blood
•Microcrystalline tests, such as the Takayama and Teichmann tests,
depend on the addition of specific chemicals to the blood so that
characteristic crystals will be formed.
Cont.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-28
Testing for Blood
•Once the stain has been characterized as blood, the precipitin
test will determine whether the stain is of human or animal
origin.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-29
Testing for Blood
•
•
•
The precipitin test uses antisera normally derived from
rabbits that have been injected with the blood of a
known animal to determine the species origin of a
questioned bloodstain.
Once it has been determined that the bloodstain is of
human origin, an effort must be made to associate or
dissociate the stain with a particular individual.
DNA analysis has allowed forensic scientists to
associate blood to a single individual.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-30
A-B-O vs. DNA
•
•
•
Prior to the advent of DNA typing, bloodstains were
linked to a source by A-B-O typing and the
characterization of polymorphic blood enzymes and
proteins.
This approach has now been supplanted by the newer
DNA technology.
DNA analysis has allowed forensic scientists to
associate blood and semen stains to a single individual.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-31
Heredity and Paternity
•
•
•
•
The transmission of hereditary material is accomplished by
means of microscopic units called genes, located on
chromosomes.
Alternative forms of genes that influence a given
characteristic (such as eye color or blood type) are known
as alleles.
Paternity testing has historically involved the A-B-O blood
typing system, along with blood factors other than A-B-O.
Currently, paternity testing has implemented DNA test
procedures that can raise the odds of establishing paternity
beyond 99 percent. How its done.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-32
Punnett Squares


Punnett Squares are
used to show the
crossing of the genes
from the mother &
father to produce the
genotype of blood type.
The Phenotype is the
physical presentation of
the organism after birth.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-33
Blood Type Genetics Example
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-34
Testing for Seminal Stains
•
•
Many of the cases sent to a forensic laboratory
involve sexual offenses, making it necessary to
examine exhibits for the presence of seminal stains.
The best way to locate and at the same time
characterize a seminal stain is to perform the acid
phosphatase (an enzyme secreted into seminal
fluid) color test.
 A purple color indicates acid phosphatase
enzyme.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-35
Testing for Seminal Stains
Semen can be unequivocally identified by either the presence
of spermatozoa or of p30, a protein unique to seminal
plasma.
Forensic scientists can successfully link seminal material to
an individual by DNA typing.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-36
Rape Evidence
•
•
•
•
The rape victim must undergo a medical examination as
soon as possible after the assault.
At that time the appropriate items of physical evidence
including clothing, hairs, and vaginal and rectal swabs
can be collected for subsequent laboratory examination.
All outer and undergarments should be carefully
removed and packaged separately in paper (not plastic)
bags.
Bedding, or the object upon which the assault took
place, may also be carefully collected.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-37
Rape Evidence
•
•
•
If a suspect is apprehended within 24 hours of the
assault, it may be possible to detect the victim’s DNA on
the male’s underwear or a swab of the suspect.
Items routinely collected from the suspect include all
clothing, pubic hair, and a blood sample or buccal mouth
swab for DNA typing.
The forceful physical contact between victim and
assailant may result in a transfer of such physical
evidence of blood, semen, saliva, hairs, and fibers.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
8-38