There are 20 questions to answer. They are numbered 4 … the blood human? To determine whether a...
61
There are 20 questions to answer. They are numbered 4-23. Read each slide. The questions (and answers) are straight off of the slides. You do not have to write the questions, just the answers.
Transcript of There are 20 questions to answer. They are numbered 4 … the blood human? To determine whether a...
There are 20 questions to answer. They are numbered 4-23. Read each slide. The questions (and answers) are straight off of the slides. You do not have to write the questions, just the answers.
Blood cells are made inside the bone
marrow
Plasma Over time, the solids in blood will settle to the bottom, leaving a clear fluid called Plasma
Serum • Characterized by its yellow hue,
and contains white blood cells and
platelets.
• Forensic analysts able to determine
the freshness of a blood sample by
examining serum (it clots several
minutes after exposure to air).
• A centrifuge can be used to
separate the clotted material from
the serum portion.
• Serum contains antibodies , proteins
floating in blood fluid, which have
significant forensic implications.
Blood Plasma contains carbohydrates, lipids, hormones, inorganic salts, proteins (such as antibodies), and clotting elements
4. Slides 1-8: Describe the parts of the blood and their functions on the back of your lab sheet.
5. Slides 8-11: Describe blood plasma or serum. Include the color.
Collection of evidence • Evidence must be collected and handled in a way that
prevents any change from taking place between the time
it is removed and the time it arrives at the lab.
Collecting tools
• The tools used in the
collection process are
as important as the
collection itself.
– Using the incorrect
tools can result in
contamination
Chain of Custody
• A written log of where evidence is and who
may have it, must be kept at all times.
• Any break in the chain will result in the
evidence being inadmissible in court
• Collection tools also
include the packaging
devices.
– In general manila
envelopes, pill bottles,
and cardboard pill
boxes are suitable
Collecting blood evidence
• When collecting blood evidence what type
of container should you use?
• If you use an airtight container then the
condensation is conducive to mold growth
and can ruin evidence.
6. What is Chain of Custody?
7. What is important to remember when collecting Blood Evidence?
The direction of travel of blood striking an object may be determined because the pointed end of a bloodstain always faces its direction of travel.
• From what direction did this blood come?
• The “tail” of a blood drop points to the direction it was moving!
8. Write this sentence:
The direction of the tail faces (the same/the opposite) as the direction of travel
SIN < = Width (a) 1.5cm
Length (c) 3.0cm
SIN < = 0.5
< = 30 degrees
9. What angle produces round drops?
Point of Origin – Draw lines through the long axis of each drop. Where the
lines converge is where the blood spatter originated – the Point of Origin.
10. How do you calculate the Point of Origin?
Can you complete this one?
Can you complete this one?
Point of
Origin
Point of Convergence (POC)
29
Blood or Unknown Stains at the
Crime Scene Whenever blood is found there are four
questions to ask:
1. Is it really blood?
2. Is the blood human?
3. From whom did the blood come?
4. How did the blood get there?
30
Is it really blood?
Luminol Test Luminol reagent is sprayed onto a surface,
in as dark of a room as possible.
If blood is present a luminescent glow will
show in the area of the blood, as it reacts
with the iron in the hemoglobin.
The Luminol test is very sensitive and can
detect bloodstains diluted up to 10,000
times!
Can be false positive with feces, urine, or
some bleaches
Luminol Test
Phenolphthalein( Kastle- Meyer’s) Test
33
Is it really blood?
Hemastix Strips Strip is moistened with distilled water and
placed on blood stain.
If blood is present, the strip will turn green.
34
Is the blood human?
To determine whether a blood sample is
from a human or animal source, samples
are tested with anti-human serum.
The forensic test consists of collecting the
blood sample in a test tube containing an
animal-derived serum containing antibodies
against human blood.
If an insoluble complex of precipitin (this
would be visible as agglutination) occurs, the
test is positive for human blood.
The precipitin test
Gel Diffusion
11. Hemostix test for what?
12. What does Luminol require to work?
13. Precipitin is also called Agglutination. Agglutination means something clumped up, or clotted. When the blood from the rabbit agglutinates, it proves that ___
From whom did the blood come?
Blood typing and/or DNA testing
(discussed later) can determine this.
History of Blood Groups and Blood Transfusions
•Experiments with blood transfusions have been carried out for hundreds of years. Many patients have died and it was not until 1901, when the Austrian Karl Landsteiner discovered human blood groups, that blood transfusions became safer. • He found that mixing blood from two individuals can lead to blood clumping. The clumped RBCs can crack and cause toxic reactions. This can be fatal.
http://nobelprize.org/medicine/educational/landsteiner/readmore.html
Early blood transfusions – approximately 50% mortality rate (1/2 the
people died)
Genetics of Blood Types
• Your blood type is established before you are BORN, by specific GENES inherited from your parents.
• You inherit one gene from your MOTHER and one from your FATHER.
• These genes determine your blood type by causing proteins called AGGLUTINOGENS to exist on the surface of all of your red blood cells.
According to the ABO blood typing system there are four different kinds of blood types: A, B, AB or O (null).
•The blood group you belong to depends on what you have inherited from your parents.
ABO blood grouping system
AUTOSOMAL CHROMOSOME
Mustafa
Sara
one allele from Mustafa and one from Sara – child will have type AB blood
The alleles for Blood group are in the same
place on the chromosome 9. Each person gets one allele from their mother, and one from their father
A B
• Antigens, usually
proteins, are located on the surface of
red blood cells and are responsible for blood-type characteristics.
14.The protein on the red blood cell is called an ____ and is responsible for the ____ _____ _____
What are blood types?
http://learn.genetics.utah.edu/units/basics/blood/types.cfm
There are 3 alleles or genes for blood
type: A, B, & O. Since we have 2 genes,
there are 6 possible combinations.
Blood Types
AA or AO = Type A
BB or BO = Type B
OO = Type O
AB = Type AB
Copyright © 2013 Crosscutting Concepts, LLC. All Rights Reserved.
www.CrosscuttingConcepts.com
Blood Types
• ABO blood group antigens present on red blood cells
• IgM antibodies present in the serum.
15.The ____ is found in the plasma and is responsible for the blood _____ when the wrong type is transfused.
Blood group A Blood group A=A Antigen On RBCs B antibodies in your blood plasma.
Blood group B Blood group B=B antigens RBCs A antibodies in your blood plasma.
AB0 blood grouping system
Blood group O Blood group O, neither A or B antigens on the surface of your RBCs Both A and B antibodies in your blood plasma.
16.What are the 4 blood types?
17.What are the 2 different blood alleles?
18.Which blood type has neither allele?
19.Which blood type has both alleles?
20.Every person gets ___ allele from their father and ____ allele from their mother.
Blood Terminology
ABO blood groups—based on having A, B, both, or no antigens on
red blood cells
Rh factor—may be present on red blood cells; positive if present and
negative if not
Antigen—a substance that can stimulate the body to make antibodies.
Certain antigens (proteins) found in the plasma of the red blood
cell’s membrane account for blood type.
Antibody—a substance that reacts with an antigen
Agglutination—clumping of red blood cells; will result if blood types
with different antigens are mixed
Blood Typing
Blood type A has antigen A on the surface of the cell and will agglutinate with blood type B.
Blood type B has antigen B on the surface of the cell and will agglutinate with blood type A.
Blood type AB has antigens A and B on the surface of the cells and will not agglutinate with either type A or type B blood.
Blood type O has neither antigen A nor B and will not agglutinate.
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-).
A+ A-
B+ B-
AB+ AB-
O+ O-
http://www.fi.edu/biosci/blood/rh.html
How common is your blood type?
46.1%
38.8%
11.1%
3.9%
21.The most common blood type is type ___.
To Test for Blood Type:
Expose blood drop to
material that reacts with
A, and with B
If the blood reacts, it is
that type
Blood Groups
Type Antigen Will kill
type:
Can Give
Blood To Can Get
Blood From
A
B
AB
O
A
B
A and B
Neither
A nor B
B or O
A or O
A, B, or O
Safe for all
A, AB O, A
B, AB O, B
AB
A, B, O, AB
A, B, O, AB
O
22.Is this OK? A person with type AB blood receives type O blood in a transfusion?
23.Is this OK? A person with type O blood receives type B blood in a transfusion?
