1. Blood and Blood Splatter By the end of this unit you will be able to:
Explain the composition of blood
Describe the function of blood cells
Determine the blood type of a blood sample
Conduct a blood splatter analysis
Examine wounds and describe the nature of the weapon
Find and process blood evidence

2. Introduction Blood typing provides class evidence
More than one person has the same blood type
A, B, AB, & O blood types
Positive (+) or Negative (-)
DNA profiling provides individual evidence

3. Introduction (cont.) A blood splatter pattern provides information
the truthfulness of an account by a witness or a suspect
the origin of the blood
the angle and velocity of impact
the type of weapon used

4. History- Blood has been studied for thousands of years

5. History- Blood has been studied for thousands of years

6. Composition of Blood Blood is a SUSPENSION of cells in a liquid
Plasma—a liquid suspending other blood components
Red blood cells (Erthrocytes)—carries oxygen to the body’s cells and carbon dioxide away

7. Composition of Blood
White blood cells (Leukocytes)—fights disease and foreign invaders and, alone, contain cell nuclei
Platelets—aids in blood clotting and the repair of damaged blood vessels

8. Review of Cell Structure
Do you remember this?
Where is the DNA located?

9. Composition of Blood

10. The Immune System
Our bodies have the ability to discriminate between their own cells and molecules (self) and foreign invaders (non self).
Identifies foreign cells or molecules (bacteria, viruses, and other parasites)

11. White Blood Cells White blood cells engulf and digest the invaders
Other white blood cells secrete antibodies
White blood cells are the ONLY blood cells with a nucleus
What does this mean?

12. White Blood Cells

13. Cellular Components of Blood

14. Blood Typing—Proteins
Discovered in 1900 by Karl Landsteiner (A, B & O)
Identifies the presence or absence of particular proteins embedded in the cell
Quicker and less expensive than DNA profiling
Produces class evidence but can still link a suspect to a crime scene or exclude a suspect
Forensic Science: Fundamentals & Investigations, Chapter 8

15. Blood Typing—Proteins
42% 12% 3% 43%
of the population in the United States
A & B proteins located on the surface of some red blood cells (RBC’s)
Type O blood has neither, Type AB has both

16. Rh Factor
85% of the population has a protein called Rh factor on their blood cells
Discovered in 1940 by Alexander Weiner, while working with Rhesus monkeys. Blood can be Rh+ or Rh-

17. Blood Type Exercises
Blood Groups, Blood Typing, and Blood Transfusions Handout
Review of Mendelian Genetics & Genetics of Bloodtyping Handout
Blood Typing “Whodunit” lab
Forensic Science: Fundamentals & Investigations, Chapter 8

18. October 4, 2011
Objective:
Forensic Science: Fundamentals & Investigations, Chapter 8

19. Blood Typing—Antibodies
Antibodies are Y-shaped proteins secreted by white blood cells that attach to antigens to destroy them
Antigens are foreign molecules or cells that react to antibodies

20. Aggutination
When antibodies are present in the plasma and a cell with foreign antigens is introduced agglutination will occur.
The Y-shaped antibody will attach to multiple antigens on different cells
This will cause a clumping, preventing blood flow that can lead to death

21. Blood Spatter
Watch CSI – Season 1, Episode 7 “Blood Drops” for introduction

22. Blood Splatter 1939—splatter patterns first analyzed
Blood may splatter when a wound is inflicted
Blood splatter pattern—a grouping of blood stains
Patterns help to reconstruct the events surrounding a shooting, stabbing, or beating

23. History of Blood-Spatter Analysis
1894 Pitorski wrote the earliest reference to blood-spatter analysis
1939 Balthazard analyzed the meaning of the spatter pattern
1955 Blood-spatter evidence used in the defense of Sam Shepard helping to exonerate him
1971 used as a tool in modern forensic examinations by Dr. MacDonnell

24. Blood Splatter Analysis
Analysis of a splatter 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

25. Properties of Blood Blood is a mixture, but it doesn’t separate easily
It is mostly water and therefore has many of the same properties (remember from biology?!?) resulting from hydrogen bonding
Cohesion – sticks to itself
Adhesion – sticks to other stuff
Surface tension – elastic outer edge

26. Blood Splatter Analysis
Natural cohesiveness of blood results in circular/round drops
On a smooth surface drops will be smooth and circular
On a porous surface (cement, wood, paper, etc.) blood will form small spikes or extensions

27. Blood Splatter Analysis
Satellite droplets—
When blood falls from a height, or at a high velocity,
It overcomes its natural cohesiveness, and
Separates from the main droplet
Spiking patterns—
Form around the droplet edges when blood falls onto a less-than-smooth surface

28. 6 Patterns/Classifications
Passive fall - Blood falling directly to floor at 90° angle results in: circular drops, with satellites if texture surface
Arterial spurts/gushes – found on walls or ceilings, caused by pumping of heart
Splashes – shaped like exclamation points, shape and position can give location of victim at time of attack
Smears – left by victim as he/she touches or brushes against a wall or furniture
Blood trails – left by victim as the move from one location to another (can be round, smeared, or spurts)
Pools – form around a victim who is bleeding heavily and left in one location

29. Blood Splatter Analysis —Six Patterns
Match each of these:
Passive drops
Arterial gushes
Splashes
Smears
Trails
Pools

30. Blood Splatter Analysis — type of wound
Spatter patterns can help determine the type of wound
Fine mist indicates high velocity impact (i.e. gunshot)
Cast-off with lower-velocity pattern indicates beating (i.e. with a pipe)
Voids (empty spaces) can determine presence of a person or an object moved after attack

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?

32. Blood Splatter Analysis
Spatter pattern can be used to determine the
angle of impact of droplets
point of impact (or convergence)
two-dimensional representation of location of the victim

33. Blood Splatter Analysis —Directionality
Remember momentum?
Darker due to its adhesive properties
The shape of an individual drop of blood provides clues to the direction from where the blood originated.
Tail points away from origin!!
How will the point of impact compare with the rest of a blood pattern?

34. Blood Splatter Analysis
Lines of convergence—two or blood splatters can pinpoint the location of the blood source

35. Crime Scene Investigation of Blood
Search for blood evidence
Determine
Is the evidence blood?
Is the blood human?
What is the blood type?
Interpret the findings:
Does the blood type match a suspect’s blood?
If not, exclude that suspect
If yes, decide if DNA profiling is necessary

36. Summary
Blood consists of cellular components and plasma.
The various human blood types are caused by the presence or absence of A and/or B proteins on the surface of red blood cells.
Blood splatter evidence can be used to recreate a crime scene.
Investigators endeavor to (a) locate, (b) identify, and (c) interpret blood splatter patterns at crime scenes.