1. Blood “Out damned spot! Out, I say
Here’s the smell of the blood still,
All the perfumes of Arabia will not
Sweeten this little hand. Oh, Oh, Oh!”
—William Shakespeare’s Lady Macbeth, in Macbeth

2. Unknown Stain at a Scene
Questions to be answered:
Is it blood?
Is it human blood?
Whose is it?
Determine blood type, alcohol content, drugs present
Determine the method(s) in which blood may have been deposited

3. Blood Evidence Class evidence for blood = blood type.
Chapter 10
Blood Evidence
Class evidence for blood = blood type.
DNA = individual evidence.
Blood stain patterns are considered circumstantial evidence in a court room. Experts argue many points including direction of travel, height of the perpetrator, position of the victim, left/right hand, whether the body was moved, etc.
Kendall/HUnt

4. Blood Spatter Evidence
Chapter 10
Blood Spatter Evidence
Deals with:
Physical properties of blood
Patterns produced under different conditions as a result of various forces being applied to the blood.
Kendall/HUnt

5. Serology Examination and analysis of body fluids.
Saliva, semen, urine, and blood.
Limited funds/time required for DNA testing - most labs still use many of the basic serology testing procedures.

6. Human vs Non-Human Blood
Microscopic observation – we will do this 
Precipitin test (Very sensitive; requires only a small amount of blood).
- blood injected into a rabbit
- antibodies are formed
- rabbit’s blood is extracted as an antiserum and antiserum is placed on sample blood.
- sample will react with human proteins if human blood is present.

7. Blood Characteristics
Plasma is the fluid portion of the blood (55%)
Cells (45%)
Erythrocytes are red blood cells. They are responsible for oxygen distribution.
Leukocytes are the white blood cells; they are responsible for “cleaning” the system of foreign invaders.
Thrombocytes or platelets are responsible for blood clotting
Serum is the liquid that separates from the blood when a clot is formed.

8. Kendall/Hunt Publishing Company
Chapter 10
Non-Human Blood
Larger nucleic red blood cells
Frog Blood
Kendall/Hunt Publishing Company
Kendall/HUnt

9. Human Blood Red blood cells are most numerous
Chapter 10
Human Blood
Red blood cells are most numerous
White blood cells are larger and less numerous
Platelets are tiny, cellular fragments
Kendall/HUnt

10. Human vs Non-Human Blood Microscopy
Chapter 10
Human vs Non-Human Blood Microscopy
Sketch the following:
One (1) HUMAN blood slide
Three (3) NON-human blood slides
(there are many to choose from)
Bullet differences
Note “what it looks like to you”
(camel, bovine, cat, dog, reptile, fish,
frog, sheep, bird, limulus)
Kendall/HUnt

11. Blood Droplet Characteristics
Chapter 10
Blood Droplet Characteristics
A blood droplet remains spherical in space until it collides with a surface
Once a blood droplet impacts a surface, a bloodstain is formed
A droplet falling from the same height, hitting the same surface at the same angle, will produce a stain with the same basic shape
Circumstantial evidence???
How will the shape change as the height is increased or decreased?
Kendall/HUnt

12. Conditions Affecting Shape of Blood Droplet
Chapter 10
Conditions Affecting Shape of Blood Droplet
Size of the droplet
Angle of impact
Velocity at which the blood droplet left its origin
Height
Texture of the target surface
On clean glass or plastic (nonabsorbent)—droplet will have smooth outside edges
On a rough surface (absorbent)—will produce scalloping on the edges
Kendall/HUnt

13. Chapter 10
Bloodstain Patterns
The harder, less porous surface, the more spatter will occur.
The pointed end of the blood stain faces the direction of travel.
A more prominent tail is visible.
Kendall/HUnt

14. Chapter 10
Bloodstain Patterns
The softer and more porous the surface, the more a blood drop will absorb into surface.
Kendall/HUnt

15. Bloodstain Geometry - Lab #1
Chapter 10
Bloodstain Geometry - Lab #1
Kendall/HUnt

16. Bloodstain Geometry - Lab #1
Chapter 10
Bloodstain Geometry - Lab #1
Use dropper to drop blood on each of the different surfaces
Each surface should be repeated a total of 4 times (1”, 2”, 36”, and 72”)
Clean lab area after each surface
Whiteboards should be cleaned with cleaner
Record data, SKETCH, and analysis questions in Lab Notebook
Kendall/HUnt

17. Questions Answered by Blood Spatter Interpretation
Distance between target surface and origin of blood
Point(s) of origin of blood
Movement and direction of person or object
Number of blows, shots, etc. causing bloodshed and/or the dispersal of blood.
Type and direction of impact that produced the bloodshed
Position of victim and/or object during bloodshed
Movement of victim and/or object after bloodshed

18. Blood Impact The more acute aoi = more elongated the stain.
Chapter 10
Blood Impact
Angle of impact—angle at which blood strikes a target surface.
The more acute aoi = more elongated the stain.
90º angles = perfectly round drops
80º angles -> more elliptical shape.
~ 30º stain begins to produce a tail.
The more acute the angle, the easier it is to determine the direction of travel.
Kendall/HUnt

19. Kendall/Hunt Publishing Company
Chapter 10
Kendall/Hunt Publishing Company
Kendall/HUnt

20. Bloodstain Patterns The shape of a blood drop:
Chapter 10
Bloodstain Patterns
The shape of a blood drop:
Round—if it falls straight down at a 90º angle.
Elliptical—blood droplets elongate as the angle decreases from 90º to 0º; the angle can be determined by the following formula:
Kendall/HUnt

21. Standardized/Theoretical Values
Chapter 10
Angle of Impact – Lab #2
Standardized/Theoretical Values
Angle
Average AOI 0˚
~ 90 ˚
15˚
~ 75 ˚
30˚
~ 60 ˚
45˚
~ 45 ˚
60˚
~ 30 ˚
75˚
~ 15 ˚
90˚
~ 0 ˚
*As the SURFACE angle increases,
the Angle of IMPACT decreases*
Kendall/HUnt

22. Area of Intersection and Convergence
Source can be determined by drawing lines from the various blood droplets to the point where they intersect.
Area of convergence is the point of origin = the spot where the “blow” occurred. May be established at the scene with measurement of angles by use of strings or lasers.

23. Bloodstain Terminology
Chapter 10
Bloodstain Terminology
Directionality—relates to the direction a drop of blood traveled from its point of origin
Terminal velocity—greatest speed a free falling drop of blood can accelerate in air. Dependent on acceleration of gravity and friction of the air against the blood—approximately 25.1 feet/second.
High velocity—greater than 25 feet per second, usually 100 feet per second; gives a fine mist appearance -> gunshot
Medium velocity—5 to 25 feet per second
Low velocity—5 feet per second or less
Kendall/HUnt

24. Angular Impact by Horizontal Motion Blood Lab #3
Chapter 10
Angular Impact by Horizontal Motion Blood Lab #3
Measure 10 ft on floor
Mark “Start” and “Finish” lines
Use phone/watch for timing
Begin moving a couple of feet BEFORE
“Start” line and end a couple of feet AFTER
Measure length and width of spatter after EACH round
Sketch pattern or cluster of stains
Kendall/HUnt

25. Bloodstain Terminology
Contact stain—bloodstains caused by contact between a wet blood-bearing surface and a second surface which may or may not have blood on it
Transfer—an image is recognizable and may be identifiable with a particular object
Swipe—wet blood is transferred to a surface which did not have blood on it
Wipe—a non-blood bearing object moves through a wet bloodstain, altering the appearance of the original stain