1. Bloodstain Pattern Analysis
Serology III
Bloodstain Pattern Analysis

2. Blood Spatter Interpretation
Forwards
Backwards

3. Oh, the stories that blood stains tell…
So far we have attempted to identify the types and looked at how DNA analysis can be done.

4. The reconstruction of how it occurred….
Now, we are going to look at physical evidence and figure out not who it came from but how it occurred…..
The reconstruction of how it occurred….

5. Types of Bloodstain Patterns
Blood drops
Impact patterns
Transfer patterns
Smears and Motion Patterns

6. What can you learn from bloodstain patterns?
Angle of deposit
Distance from target
Direction of travel
Trails
Object that caused the pattern
Time since deposit
Volume of blood

7. Factors Affecting Bloodstain Patterns
Energy/Speed
Low
Medium
High
Distance
Target surface
Angle of deposit

8. Target Surface

9. Low Velocity Patterns
Low velocity spatters happen when an object moving less than 5 ft/sec strikes a surface, with drops that are 4mm or larger in size.
Example: Blood dripping only under the influence of gravity…. The drop will change shape depending on whether or not the source is standing still or moving

10. Low-Velocity Pattern

11. Low Velocity Patterns cont.
Arterial bleeding – If an artery is damaged during an assault, suicide attempt or accident, the blood loss may take the form of gushes or spurts.

12. Low Velocity Patterns cont.
Cast-off blood – blood that is flung from an object

13. Cast-off blood tends to be a fairly uniform trail of droplets
Cast-off blood tends to be a fairly uniform trail of droplets. You can figure out the point of convergence as well as the number of blows with the weapon that made contact to the victim. You can figure out the position of the assailant, the height of the perpetrator and even if the assailant was right or left handed.

14. Ahhh…now the Medium Velocity Spatters
Medium–velocity spatters come from objects moving between ft/sec. The spatters are generally smaller than the big ol’ low velocity ones. They vary from one to four millimeters in diameter.
Example – Spatters caused by blunt objects

15. Medium-Velocity

16. Some Low, Some Medium

17. High Velocity Spatters
High-velocity spatters occur when an object strikes a victim at a speed faster than 100 ft/sec. The spatters are very small, mist-like patterns and are generally less than 1 millimeter in diameter.
Example: A bullet produces spatters near an entrance wound or an exit wound.

18. High Velocity Spatter
FYI: The spatter that a bullet causes is different depending on whether the bullet is entering or exiting the victim.

19. Which way did it go?
A drop of blood ‘on the move’ will leave a tail. The tail points to the direction that the blood was traveling. This would then reveal the direction of the origin.

20. Where did the blood come from?
Click on hammer!

21. Angles

22. Ellipse

24. Angle of Impact
Now that we know how to figure out the direction of travel, we can determine the angle of impact. Take out your calculators.
Sine of impact angle = width of bloodstain (mm)
length of bloodstain (mm)

25. Math time….
Suppose that a drop of blood measures 10 mm in width and 18 mm in length. At what angle did the drop hit the target?

26. Area of Convergence
The area of convergence represents the point from which a stain emanated.

27. Area of Convergence

28. Void Patterns
A void pattern is an absence of blood spatter in an area where you’d otherwise expect to see them. Many times something blocks the spatter and creates what looks like a white shadow among spatter patterns. Many times this void indicates where the attacker stood.

29. Transfer Patterns Contact Transfer Motion: Wipe vs Swipe
So, there is a difference?

30. Transfer patterns result when an object soaked with blood comes in contact with an unstained object.
Example: Bloody fingerprints and shoeprints

31. What caused the transfer of these patterns?
How specific can you be?

32. Are you telling me that there is a difference between a wipe and a swipe ?

33. To wipe or to swipe, that is the question…
Wipe - pattern created when a secondary target moves through an existing wet blood stain on some other object
Swipe - the transfer of blood onto a target (clean) surface by a bloody object that is usually moving laterally

34. After all, you don’t call them windshield swipers, right?

35. Facts About Blood Accounts for 8 % of total body weight
5 to 6 liters of blood for males
4 to 5 liters of blood for females
A 40 percent blood volume loss = irreversible shock (death)
A blood loss of 1.5 liters = incapacitation

36. Homework Questions
Describe the different types of blood stain patterns.
What can you learn from bloodstain patterns?
Give examples for low, medium and high velocity patterns.
What is a void pattern?
What is the difference between a wipe and a swipe?