ilide.info-03-blood-and-blood-stains-forensic-chemistry-pr_f414dc37eb47827b4a6cf056534d995e.pdf

blood and blood stain pdf for information

1. Blood and Blood Stains

2. Topic Outline
1. Nature of Blood
2. Sampling, Handling and Preserving Blood
samples and Techniques

3. ACTIVATING
PRIOR KNOWLEDGE
Out of all the movies you have watched, what are
some of the movies you have watched that had a
crime scene wherein the blood was important or
vital in catching the criminals?
For you, how important is finding blood in a crime
scene?

4. Nature of Blood
The study of blood is essential in criminology
since this type of evidence is usually in violent
crimes such as murder, rape, robbery, assault,
and many more.
Understanding the nature of blood and different
techniques is vital in solving a lot of these crimes.

5. Nature of Blood
Blood is the red fluid that can be found in the body. Its
primary function is:
To supply oxygen to tissues (they are bound to hemoglobin,
which is carried by the red cells)
Supply nutrients
Remove wastes
Has Immunological functions
Responsible for coagulation
 Transports hormones and signal tissue damage.

6. Nature of Blood
Blood composes 8% of the body weight.
Its components are plasma, RBC, WBC and platelets.
Its color is due to the hemoglobin, which is also
responsible for transporting O2 and CO2 to the lungs.
It has a clear liquid (serum) that separates when blood
clots. Clotting is a defense mechanism to prevent blood
loss.

7. Erythrocytes or RBC
RBCs, also called erythrocytes (Greek erythrose, red; ytes, cell)
They are non-nucleated, biconcave-shaped cells measuring about 7.8
um diameter (unfixed).
RBCs lack organelles and consist only of a plasma membrane,
underlying cytoskeleton, hemoglobin, and glycolytic enzymes.
They are filled with 02-carrying protein called hemoglobin and are
the only blood cells that is able to not leave the vasculature.

8. Erythrocytes or RBC
"Humanrbc1000x" by John Alan Elson is licensed under
CC SA 3.0

9. Leukocytes or WBC
WBCs also called leucocytes are functional as they leave the blood and
goes to the tissues and conducts various work that helps in the
immunity of the body.
Leukocytes are divided into two major groups: granulocytes and
agranulocytes, based on their cytoplasmic granules' density.
All leukocytes are vital players in the constant defense against invading
microorganisms and repair damaged tissues, explicitly leaving the
microvasculature in injured or infected tissues.
Age, sex and physiologic conditions of a person has an effect on the
number of leukocytes in the blood.
Healthy adults have 4500-11,000 leukocytes per microliter of blood.

10. Leukocytes or WBC
"WHITE BLOOD CELL IN ELECTRON MICROSCOPE" by
Eladia Henning is licensed under CC0.

11. Platelets or Thrombocytes
Blood platelets (or thrombocytes) are tiny non-nucleated,
membrane-bound cell fragments only 2-4 μm in diameter.
Platelets originate by separation from the ends of cytoplasmic
processes extending from giant polyploid bone marrow cells
called megakaryocytes.
Platelets promote blood clotting and help repair minor tears or
leaks in small blood vessels' walls, preventing loss of blood
from the microvasculature.
Normal platelet counts range from 150,000 to 400,000/μL
(mm3) of blood.

12. Platelets or Thrombocytes
Circulating platelets have a life span of about ten days.
In stained blood smears, platelets often appear in clumps.
Each platelet is generally discoid, with a very lightly stained
peripheral zone, the hyalomere, and a darker-staining
central zone rich in granules, called the granulomere.
A sparse glycocalyx surrounding the platelet plasmalemma is
involved in adhesion and activation during blood coagulation
—the role of platelets in controlling blood loss (hemorrhage)
and in wound healing.

13. Platelets or Thrombocytes
"Thrombocytopenia" by Prof. Erhabor Osaro is licensed
under CC SA 4.0

14. Platelets or Thrombocytes
Circulating platelets have a life span of about ten days.
In stained blood smears, platelets often appear in clumps.
Each platelet is generally discoid, with a very lightly stained
peripheral zone, the hyalomere, and a darker-staining
central zone rich in granules, called the granulomere.
A sparse glycocalyx surrounding the platelet plasmalemma is
involved in adhesion and activation during blood coagulation
—the role of platelets in controlling blood loss (hemorrhage)
and in wound healing.

15. Sampling, Handling and Preserving
Blood samples and Techniques

16. Location
Strong oblique lights are used to examine the area,
articles, and clothing suspected to bear bloodstain.
UV (Ultraviolet), colored, and IR (Infrared) is also used.
IR locates bloodstains in colored objects (Photographs with
IT rays can also reveal blood spots).
A chemical called luminol is used to react with blood that
gives it fluorescence that makes the bloodstains visible.
Even decomposed blood reacts with the reagent.

17. Collection
A. Liquid Blood (Blood Pools)
You should collect two samples (5cm3 each) in clean test tubes or
vials.
In one of the samples, add sodium fluoride, oxalate, or citrate.
In the other, add no preservative for blood.
Seal them and cooled in a thermal box.
Collect the third sample in a piece of clean rag (3cm2).
The stain is dried and packed in a clean envelope or bottle, and
the material should be uncontaminated.

18. Collection
B. Wet Stains
A clean piece of rag or filter paper is taken and pressed against the stain.
If the stain is partially dry, the piece should be moistened with saline
solution and is pressed against the stain.
If the stain is a non-absorbent surface, it is allowed to dry, and the article
is collected.
If the stain contained sufficient liquid blood, it is collected in the same
way as liquid blood.
If the stain is on an absorbent surface and has penetrated the surface and
is allowed to dry and the article is collected.
A “control” from the place near the stained are also collected.

19. Collection
C. Dry Stains
Clothes
You should take the piece of clothing and record the stains' number,
position, and size correctly. Stains on different parts of the clothing
piece are not allowed to contaminate one another through cracking or
getting dislodged during packing on transit.
Absorbent Surfaces
Absorbent surfaces absorb the blood. For correct sampling, stained
and unstained materials are separately collected, as described in the
preceding notes.

20. Collection
Non-absorbent Surfaces
It would help if you collected the articles whenever possible. You
should moisten the clean piece of cloth or filter paper with a saline
solution and press it against the stain. Use an inert gum and stick it to
the moistened surface. Peel off when it dries as the stain is
transferred to the peeled piece.
Grass
Start to tie the grass with a thread. After that, cut the tuft and dry it.
Pack it in an envelope or glass jar. Make sure that the blood does not
get dislodged in the process.

21. Collection
Body
If you found blood in the hair, collect it by combining the hair.
 Cut and collect the hair if possible.
If you found blood in the fingernails, you could scrape out with a clean
toothpick.
 “Control” from an unstained fingernail should also be collected.
Cutting of fingernails should not be done.
If you find blood in other parts of the body; a wet piece of clean rag or filter
paper is pressed against the stain.
If the stain is adhering firmly to the body, it can be moistened with an inert
gum solution.