Transcript Is the stain blood?

Blood Basics and Other Body
Fluids
Objectives:
• Distinguish between blood types and their antigens
and antibodies.
• Explain what happens in the process of agglutination.
• Use whole blood typing to type blood.
• Explain what tests are used to characterizing a stain as
blood.
• Explain the significance of the precipitin test in
serology.
• Discuss the contribution of polymorphic enzymes and
proteins to blood’s individualization.
• Define chromosomes and genes.
• Use Punnett squares to determine the
probability of inheritance.
• Describe lab tests for seminal stains.
• Preservation of stains for lab examination.
• List the steps for collection of physical
evidence in rape investigation.
History
A. 1901- Karl Landsteiner discovered that people had different types of
blood. From his work the ABO classification system of blood types was
developed.
B. By 1937 the Rh factor was discovered.
C. At present over 100 different blood factors have been shown to exist,
but the ABO factors are still the most important for properly matching a
donor with a recipient.
1. If a forensic scientist individualized human blood by
Identifying all of the known blood factors, the resulting
evidence would be of the strongest kind for linking a suspect
to the crime scene.
D. With the advent of DNA technology, the blood typing has taken on a
secondary role. The analysis of the DNA found in blood individualizes a
blood sample with a very high degree of reliability.
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.
Components of Blood
Red Blood Cells
(Erythrocytes)
White Blood
Cells
(Leukocytes)
Platelets
(Thrombocytes)
Plasma
Components of Blood
Red Blood Cells
(Erythrocytes)
Red in color (hemoglobin is ironcarrying), made in the bone marrow, live
120 days, removed when damaged by
liver and spleen (made into bile), carry
O2, no nucleus, 30 trillion per body, …
White Blood
Cells
(Leukocytes)
Protect body from disease, have a nucleus,
colorless, may diff. kinds, make antibodies,
made in bone marrow and lymph nodes, 60
billion per body, …
Platelets
(Thrombocytes)
Cell fragments, no nucleus, involved in
blood clotting, made in bone marrow,
formed by pinching off of cytoplasm from
large cells, 1.5 trillion per body, produced
200,000 per day, live 7 days, …
Plasma
55% of the volume of blood, clear, straw
colored liquid, 90% water, contains
dissolved gases, nutrients, hormones,
wastes, salts, enzymes, plasma proteins, …
Comparing Animal Blood
What is 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.
• The concept of specific antigen-antibody reactions
has been applied to immunoassay techniques for
the detection of drugs of abuse in blood and urine.
Blood Facts
• The average adult has about FIVE liters of blood inside of
their body, which makes up 7-8% of their body weight.
• Blood is living tissue that carries oxygen and nutrients to
all parts of the body, and carries carbon dioxide and other
waste products back to the lungs, kidneys and liver for
disposal. It also fights against infection and helps heal
wounds, so we can stay healthy.
• There are about one billion red blood cells in two to three
drops of blood. For every 600 red blood cells, there are
about 40 platelets and one white cell.
Erythrocytes
• Transport oxygen from the lungs to the
body tissues
• Transport carbon dioxide from the tissues to
the lungs
• Red cells possess chemical structures on
their surfaces called antigens or
agglutinogens
– impart blood type characteristics
Blood Type
• Your blood type is determined before you are BORN, by
specific genes inherited from your parents.
• Three types (alleles) of blood type gene
– A, B, O
• Each individual inherits one blood type gene from their
mother & one from their father
– 6 possible combinations (genotypes)
• AA, BB, OO, AB, AO, and BO
• These genes determine your blood type by causing proteins
(or carbohydrates) called ANTIGENS (or agglutinogens)
to exist on the surface of all of you red blood cells.
Antibodies or Agglutinins
• Proteins that are present in the serum
• responsible for ensuring that the only blood
cells that can survive in a person are cells of
the correct blood type
Antigen-Antibody Reaction
• B-Antibodies produced by people with type
A blood remove any red blood cells
containing B antigens by clumping them
together
• A- Antibodies produced by people with B
blood remove any red blood cells
possessing A antigens
Type O Blood
• Possessed by people whose genotype is OO
– both parents passed on the O gene
– have no antigens
• these cells can be introduced into a person with
Type A or Type B because these cells are not
attacked by the antibodies these people possess
– have both A & B antibodies
• can only have other O type cells mixed with this
blood
Type A
• Possessed by people with genotype
– AA
– AO
• A is dominant to O
• Possesses antibody B
– will destroy any Type B red cells
– compatible with A or O red cells
Type B
• Possessed by people with genotype
– BB
– BO
• B is dominant to O
• Possesses antibody A
– will destroy any Type A red cells
– compatible with B or O red cells
Type AB
• Possessed by people with genotype
– AB
• A & B are co-dominant
• Possesses no antibody
– can have A, B, AB, or O cells added
– Can’t be added to any other blood type without
being destroyed by an antibody
What Type is it?
• Blood typing is done by reacting whole
blood with antibody A and antibody B
Blood Typing
Anti-A
+ Blood
+
Anti-B
+ Blood
-
Antigen
Present
A
Blood
Type
A
-
+
B
B
+
+
A and B
AB
-
-
Neither
A or B
O
How Common Is Your Blood
Type?
46%
39%
11%
4%
A+ AB+ BAB+ ABO+ O-
Rh Factors
Scientists sometimes study Rhesus monkeys to learn more
about the human anatomy because there are certain
similarities between the two species. While studying Rhesus
monkeys, a certain blood protein was discovered. This
protein is also present in the blood of some people. Other
people, however, do not have the protein.
The presence of the protein, or lack of it, is referred to as
the Rh (for Rhesus) factor.
If your blood does contain the protein, your blood is said to
be Rh positive (Rh+). If your blood does not contain the
protein, your blood is said to be Rh negative (Rh-).
Secretors
• An individual who secretes his or her blood
type antigen(s) in all body fluids.
Approximately 80% of the population are
secretors.
Blood Enzymes and Proteins
• Enzymes: proteins that have important functions in regulating the
body’s chemistry.
• Enzymes have the characteristic of existing in different forms
(polymorphic) and can be separated into protein components called
iso-enzymes.
• A common polymorphism is Hb, which causes sickle-cell anemia.
• Iso-enzymes can be separated by electrophoresis.
• Forensic serologists have studied these iso-enzymes with the goal of
being able to individualize blood samples found at crime scenes.
• While there are many iso-enzymes in blood, only those that survive the
drying and aging process are useful to the forensic serologist.
Iso-enzymes and Probability
• Each of these protein and enzyme variants, as well as all blood
subtypes, have known distributions in a population.
• It's therefore a simple matter to calculate probability estimates that
border on individualized blood typing.
• Probability is defined as the frequency of an event occurring.
• If there are several event that may occur, the overall probability will be
the product of these probabilities.
• Probability is usually expressed in per cent (i.e., 25%), while the
frequency of an event is expressed as a decimal value (i.e., 0.25)
• At a crime scene, a blood sample and the suspect’s blood had the
following characteristics: A blood (42%), basic subtype A2 (25%),
protein AK (15%) and enzyme PGM 2 (6.0%). What is the frequency
of occurrence of these blood characteristics in the general population?
• Answer: 0.00094 (0.42 X 0.25 X 0.15 X 0.06) or 0.094% probability!
BLOODSTAIN
CHARACTERIZATION
• Bloodstain analysis traditionally follows the following
steps:
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–
–
–
Is the stain blood?
Is the stain animal or human blood?
If human blood, what type?
Can the sex, age, and race of the source of blood be determined?
• Is the stain blood?
– The benzidine test was long used until replaced by the Kastle-Meyer test.
Benzidine was found to cause cancer.
– Both tests are color tests based on the observation that hemoglobin will oxidize
several classes of organic compounds.
– Kastle-Meyer color test- when the reagent- phenolphthalein is mixed with
hemoglobin in blood, the clear phenolphthalein will turn a deep pink.
• Not a specific test for blood, some vegetables react with the reagent in the
same way, for example potatoes and horseradish.
• From a practical point of view, a positive Kastle-Meyer test indicates blood
because how often will potatoes or horseradish contaminate a crime scene?
BLOODSTAIN
CHARACTERIZATION
Is the stain blood?
• Another test used is a Hemastix® strip, which will turn green in the
presence of blood.
• Luminol is an important presumptive identification test for blood. The
iron in hemoglobin reacts with the luminol and causes the emission of
light (luminescence). Needs to be done in a dark room.
– Extremely sensitive test- can detect
bloodstains diluted to 300,000 times.
– Spraying large areas is possible
– Does not interfere with subsequent
DNA tests.
BLOODSTAIN
CHARACTERIZATION
• microcrystalline tests- Takayama and Teichmann tests
– Both depend on the addition of specific chemicals to the blood so
that the characteristic crystals with hemoglobin derivatives will be
formed.
– Crystal tests are far less sensitive than color tests and they are more
susceptible to interference from contaminants that may be present
in the stain.
BLOODSTAIN CHARACTERIZATION
Is the stain animal or human blood?
To answer this question, forensic serologists use antiserum tests.
The standard test is called the precipitin test
This involves forming antibodies to human blood in an animal.
The animal serum thus treated will cause a precipitate to form
when reacted with human blood.
Precipitin test is very sensitive and requires
only a small amount of blood for testing.
Extracts from mummies 4-5 thousand
years old have given positive reactions to
this test. So the age of the blood tested can
be very old.
Also, bloodstains diluted by washing in
water still give positive precipitin tests
BLOODSTAIN
CHARACTERIZATION
• Gel diffusion- takes advantage of the fact that antibodies
and antigen will move toward each other on an agar gelcoated plate forming a line of precipitate in between the
two.
• Electrophoretic method- an electric potential is applied to
the gel medium; the antibodies and antigens move toward
each other forming a line of precipitate in between the two,
but the process is quickened.
Principles of Heredity
• Transmission of Traits
– 1.Antigens, proteins and enzymes that have been previously
discussed are genetically controlled traits.
– Accomplished by genes, which is the basic unit of heredity.
– Genes are on chromosomes (46 in 23 pairs). Each chromosome in
a pair has the same genes in the same order at the same spot.
– The human egg and human sperm contain 23 chromosomes, which
combine during fertilization.
•
•
•
•
A female has XX chromosome, and male has XY chromosome.
Genes and chromosomes come in pairs.
The position of a gene on the chromosome is called the locus.
Alleles are alternative forms of genes that influence an inherited
characteristic.
• An example of allele genes is the A-B-O blood type system.
• Genotype- the exact allelic combination
• Phenotype- the physical appearance of the organism as a result of the
genotype.
Principles of Heredity
• Transmission of Traits
• A-B-O blood types:
– When a gene is made of two similar genes, they are said to be
homozygous. Examples include AA ,BB , or OO.
– If the gene is made up of two different genes, it is said to be
heterozygous. An example would be AB, AO, or BO.
– A and B genes are dominant, while O genes are recessive.
– A pair of A-B-O allele genes together are the genotype of an
individual.
– The phenotype of an individual is the outward characteristic of the
individual.
– There is no lab test to determine a person’s A-B-O genotype.
– If the genotypes of both parents are known, a Punnett square may
be constructed to determine potential genotype of offspring.
Paternity Testing
• Blood typing can be used to resolve cases of disputed
paternity.
• The more blood groups tested, the more certain one can be
that the suspect is indeed the father.
– HLA (human leukocyte antigen) test relies on identifying a
complex system of antigens that exist on the surface of white blood
cells. If a suspect cannot be excluded as fathering a child after this
test is performed then there is a 90% chance that he is the father.
– DNA testing has raised the odds of establishing paternity to
beyond 99%.
• ( Do the punnett square in your notes- OO x AB and then
go to the last page of your notes to do the practice sheet
on paternity.)
Forensic Characterization of
Semen
• Tests used to locate seminal stains– Acid phosphatase color test- acid phosphatase is an enzyme
secreted by the prostate into seminal fluid. Its concentrations in
seminal fluid are 400 times greater than in any other body fluid.
Moistened filter paper is rubbed on suspect fabric or surfaces and
then Fast Blue B solution is applied. This enzyme will turn purple
in the presence of Fast Blue B solution. A reaction time of less
than 30 seconds indicates the presence of semen. (Other substances
will react but not as fast.)
– MUP test- Moistened filter paper is pressed against a suspected
garment and then MUP solution is sprayed onto the paper. Under a
UV light semen stains will fluoresce.
Acid Phosphatase Test
• The more semen, the deeper the purple
Forensic Characterization
of Semen
• Microscopic identification of spermatozoa. Sperm are elongated
structures 50-70 microns long. The criminalist would immerse the
stained material in distilled water, stir rapidly, dry the fluid on a slide
and examine under 400x. it is difficult to locate sperm this way due to
several reasons:
• Sperm bind tightly to cloth materials
• They are extremely brittle when dry and easily disintegrate.
• Many sex crimes involve individuals with low sperm counts, a
condition known as oligospermia, or they may involve individuals with
no sperm at all, a condition known as aspermia.
• Today, forensic scientists can link seminal material to one individual
with DNA technology.
Collection of Rape Evidence
• Finding evidence of rape:
– Physical injuries such as bruises or bleeding tend to confirm the
fact that a violent crime took place.
– Forceful physical contact will result in transfer of physical
evidence- blood, semen, hairs, and fibers. This evidence will help
forge a link between the between the crime and the criminal.
• Protection of Physical Evidence– Place a clean bed sheet on the floor and lay clean paper over it.
– The victim removes their shoes and stands on the paper.
– All outer and inner garments of the involved parties should be
carefully removed and placed in separate paper bags one item at a
time to avoid cross contamination. The paper collects any loose
foreign material that falls from the clothing.
– The paper should be then folded so that all
foreign materials will be contained inside.
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•
•
•
•
•
– The bedding or object upon which the assault took place should be
submitted to the lab for processing. Items suspected of containing
seminal stains must be handled carefully to avoid the loss of
material.
– If it is not possible to transport the stained article, the stained area
should be cut out and submitted with an unstained piece as a
substrate control.
– The rape victim must be examined by medical personnel as soon as
possible after the assault. At this time the appropriate items of
physical evidence should be collected by trained personnel. The
following evidence should be collected:
Pubic combings
Hair- pubic and head for standard reference
Smear- vaginal, rectal and oral- for DNA typing
Blood sample- for toxicology testing
Fingernail scrapings
Urine- for drug testing (GHB, Rohypnol)
Saliva residues for DNA typing
Collection of Rape Evidence
• If the suspect is apprehended the following items are routinely
collected:
– all clothing
– Pubic hair combings
– Pulled head
– hair and pubic hair for standard references
– Penile swab
– A blood sample
Vocabulary:
• DNA: abbreviation for deoxyribonucleic
acid- the molecules carrying the body’s
genetic information. DNA is double-stranded
in the shape of a double helix
• Plasma: the fluid portion of unclotted blood
• Serum: the liquid that separates from the
blood when a clot is formed
• Antigen: a substance, usually a protein that
stimulates the body to produce antibodies
against it
• Antibody: a protein that destroys or inactivates a
specific antigen. Antibodies are found in the blood
serum
• Antiserum: blood serum in which there are specific
antibodies
• Agglutination: the clumping together of red blood
cells by the action of an antibody
• Serology: the study of antigen-antibody reactions
• Hemoglobin: a red blood cell protein responsible for
transporting oxygen in the bloodstream and the red
coloring of blood
• Precipitin: an antibody that reacts with its
corresponding antigen to form a precipitate
• Secretor: an individual who secretes his or
her blood-type antigen(s) in body fluids.
Approximately 80 percent of the population
are secretors
• Enzyme: a type of protein that acts as a
catalyst for certain specific reactions
• Polymorphism: the existence of more than
one form of genetic trait
• Iso-enzymes: multiple molecular forms of an
enzyme, each having the same or very similar
enzyme activities
• Gene: a unit of inheritance consisting of a
DNA segment located on a chromosome
• Chromosome: a rodlike structure in the cell
nucleus, along witch the genes are located. It
is composed of DNA surrounded by other
material, mainly proteins
• Egg: the female reproductive cell
• Sperm: the male reproductive cell
• Zygote: the cell arising from the union of an
egg and a sperm cell
• X-chromosome: the female sex chromosome
• Y-chromosome: the male sex chromosome
• Locus: the physical location of a gene on a
chromosome
• Allele: any of several alternative forms of a
gene located at the same point on a particular
pair of chromosomes. For example, the genes
determining the blood types A and B are
alleles
• Homozygous: having two identical allelic
genes on two corresponding positions of a pair
of chromosomes
• Heterozygous: having two different allelic
genes on two corresponding positions of a pair
of chromosomes
• Genotype: the particular combination of
genes present in the cells of an individual
• Phenotype: the physical manifestation of a
genetic trait such as shape, color, and blood
type
• Acid phosphatase: an enzyme found in high
concentration in semen
• Oligospermia: a condition describing an
abnormally low sperm count
• Aspermia: the absence of sperm; sterility in
males