1. Blood & Blood Spatter

2. Blood and Blood Spatter OBJECTIVES:
explain the composition of blood
describe the function of blood cells
determine the blood type of a blood sample
conduct a blood spatter analysis
examine wounds and describe the nature of the weapon
find and process blood evidence
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Forensic Science: Fundamentals & Investigations, Chapter 8

3. Introduction and History
Blood typing can provide class evidence; whereas DNA profiling can provide individual evidence.
A blood spatter pattern can give information about the truthfulness of an account by a witness or a suspect.
It also can provide information about the origin of the blood, the angle and velocity of impact, and type of weapon used.
Our understanding of blood began in ancient times and continues to grow today.
Forensic Science: Fundamentals & Investigations, Chapter 8

4. (brief) History of Blood
2500 BCE – Egypt – bloodletting to “cure” disease
1659 – Leeuwenhoek viewed blood cells w/ microscrope
1901 – Landsteiner – three major blood types (A,B, O)
Forensic Science: Fundamentals & Investigations, Chapter 8

5. Review…
In 2500 BCE what method of curing illness was used in what country?
In 1659 the biologist Leeuwenhoek is credited for doing what?
In 1901 what contribution to blood analysis did Landsteiner make?
Forensic Science: Fundamentals & Investigations, Chapter 8

6. Blood Function
Transport of substances (O2, CO2, nutrients, waste, heat, hormones)
Regulation (pH, temperature, hydration)
Defense (blood loss, microbes, toxins)
Forensic Science: Fundamentals & Investigations, Chapter 8

7. Composition of Blood
Whole blood carries cells and plasma—the fluid with hormones, clotting factors, and nutrients.
Shown above respectively:
Red blood cells (RBC / erythrocytes) - disc shaped cells that carry oxygen to the body’s cells and carbon dioxide away.
White blood cells (WBC / leukocytes) fight disease and foreign invaders and, alone, contain cell nuclei.
Platelets aid in blood clotting and the repair of damaged blood vessels.

8. What is Blood? - YouTube (https://www.youtube.com/watch?v=CRh_dAzXuoU)
Forensic Science: Fundamentals & Investigations, Chapter 8

9. REVIEW… Name three main functions of blood.
Name at least two specific example of each of these functions.
Explain what blood plasma does.
Name the three type of cells in blood.
Explain each of these type of cells’ function
Forensic Science: Fundamentals & Investigations, Chapter 8

10. Blood Facts The average Human has 5 liters of blood.
This is about 7% to 8% of your body weight.
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.
Forensic Science: Fundamentals & Investigations, Chapter 8

11. Blood Facts
Blood is considered living tissue that carries oxygen and nutrients to all parts of the body.
It also fights against infection and helps heal wounds, so we can stay healthy.
Forensic Science: Fundamentals & Investigations, Chapter 8

12. Review Blood Facts
How many liters of blood does the average human body have?
Approximately what percentage is this of your weight?
About how many RBC are in a couple drops of blood?
What is ratio of platelets and WBC to RBC’s?
Forensic Science: Fundamentals & Investigations, Chapter 8

13. Antigens
An antigen is any substance that causes your immune system to produce antibodies against it. An antigen may be a foreign substance from the environment such as chemicals, bacteria, viruses, or pollen. An antigen may also be formed within the body, as with bacterial toxins or tissue cells.
Forensic Science: Fundamentals & Investigations, Chapter 8

14. Antibodies
An antibody is a protein produced by the body's immune system when it detects harmful substances, called antigens.
The antibodies can act themselves to disable an intruder,(antigens),or they can attract killer cells called macrophages to destroy antigens.
Forensic Science: Fundamentals & Investigations, Chapter 8

15. These % are important for later on.
Blood Typing
42% % 3% %
of the population in the United States
(of which 85% is Rh+)
Cell surface proteins (proteins on cell/plasma membrane) determine blood types
There are other proteins that can help identify blood such as Rh (Rhesus factor). Blood cells with RH proteins are said to be positive. Those without are negative.

16. Blood Typing O = Universal Donor (gives to everybody).
A can give to A or AB.
B can give to B or AB.
AB can give to no one but take from everyone.
Forensic Science: Fundamentals & Investigations, Chapter 8

17. Blood Typing If you mix A blood & B blood, what will happen?
Forensic Science: Fundamentals & Investigations, Chapter 8

18. Blood Typing
Agglutination – clumping of RBCs - Foreign blood type reacts w/ regular blood type & an immune response occurs (agglutination)
Forensic Science: Fundamentals & Investigations, Chapter 8

19. Blood typing
How could you use agglutination to help you blood type accurately?
Brain storm with your groups.
Forensic Science: Fundamentals & Investigations, Chapter 8

20. Review Blood Typing Describe what antigens are.
Describe what antibodies are.
Name the 8 types of blood, their antigens, antibodies and RH factor.
Describe agglutination.
Forensic Science: Fundamentals & Investigations, Chapter 8

21. Blood Spatter Analysis
Analysis of a spatter pattern can aid in determining the:
direction blood traveled.
angle of impact.
point of origin of the blood.
velocity of the blood.
manner of death.
Forensic Science: Fundamentals & Investigations, Chapter 8

22. Blood Spatter
In 1939 the meaning of the spatter pattern was first analyzed.
When a wound is inflicted, a blood spatter pattern may be created.
It takes a grouping of blood stains to make a blood spatter pattern.
The pattern can help to reconstruct the events surrounding a shooting, stabbing, or beating.
Forensic Science: Fundamentals & Investigations, Chapter 8

23. Blood Spatter Analysis
When blood falls from a height or at a high velocity, it can overcome its natural cohesiveness and form satellite droplets.
When it falls onto a less-than-smooth surface, it can form spiking (spines) patterns around the drops.
Forensic Science: Fundamentals & Investigations, Chapter 8

24. Blood Splatter Lab continued
Make a data table of speeds & shape of drops.
Drop blood as you walk slowly.
Drop blood as you walk faster.
Drop blood as you run.
Write the following questions down and answer:
How do the drop differ at different speeds?
Why would there be these differences?
Forensic Science: Fundamentals & Investigations, Chapter 8

25. Blood Drop Height Lab
Was there a noticeable difference in the size of splatter from height to height? Explain
 How much difference was there between the smallest spatter and the largest? Explain
Do you trust your results or were there problems with your experiment? 
What are your conclusions?
Forensi Science: Fundamentals & Investigations, Chapter 8

26. Angle of Impact (AOI)
The AOI for representative bloodstains helps to generate the 3rd dimension
(z-axis) in a crime scene.
This shows how high up off the ground the impact occurred.

27. Blood Spatter Analysis—Directionality
The shape of blood drops gives an idea of the direction of impact. How will the point of impact compare with the rest of a blood pattern?
Forensic Science: Fundamentals & Investigations, Chapter 8

29. Blood Spatter Analysis—Location of the Origin of the Blood
Lines of convergence
Draw straight lines down the axis of the blood splatters.
Where the lines converge, the blood originated.
Forensic Science: Fundamentals & Investigations, Chapter 8

30. Blood Spatter Analysis—Six Patterns
Describe each of these based on the images above:
a. passive drops
b. arterial gushes
c. splashes
d. smears
e. trails
f. pools
Forensic Science: Fundamentals & Investigations, Chapter 8

31. Blood Splatter Analysis—Impact
Patterns can help investigators determine the type of weapon used.
What kind of a pattern is produced by a gun shot?
What kind of a pattern is produced by a hammer blow?
Forensic Science: Fundamentals & Investigations, Chapter 8

32. Crime Scene Investigation of Blood
Search for blood evidence.
If any is discovered, process it determining:
Whether the evidence is blood.
Whether the blood is human.
The blood type.
Interpret the findings:
See if the blood type matches a suspect.
If it does not, exclude that suspect.
If it does, decide if DNA profiling is needed.
Forensic Science: Fundamentals & Investigations, Chapter 8